Sampling strategy and selection of material

Fieldwork was undertaken in the highlands of the central Andes between 2015 and 2022 covering all species of Caryophyllaceae. Herbarium specimens were collected with duplicates and corresponding leaf tissue was dried in silica gel. Collecting focused on eight Andean departments of Peru (c. 200 localities), allowing us to cover most of the type localities of previously described species in Arenaria, Pycnophyllopsis and Stellaria as hitherto classified. In addition, herbarium material was evaluated from B and several other herbaria from which material was loaned to B (GOET, L, LPZ, O and PRC) and sampled for molecular analysis in case the respective taxon was not found in the field. The following institutions were visited: CONC, CUZ, F, GOET, HSP, HOXA, HUT, K, LP, LPB, LPZ, MO, MOL, NY, P, PRC, SI, US and USM (herbarium codes according to Thiers continuously updated).

Following a first round of phylogenetic assignment of the material to major clades using short sequences (plastid trnL-F and nrITS) that could easily be generated for many samples following the approach of Mansion & al. (2012), a fraction of these samples including species from all three genera mentioned above turned out to belong to a very distinct subclade of a Stellaria clade. Further research then focused on these samples. To determine the precise position of this subclade, the sampling was extended to represent all major lineages of Stellaria, guided by the trees of Sharples & Tripp (2019).

Compilation of all previously published names / taxa

A list of Arenaria names was received from the WFO Data Centre in February 2018 and imported into the EDIT Platform. This import included names accepted in the WFO backbone and their synonyms therein (WFO 2018). For Plettkea, Pycnophyllopsis and Stellaria, the names were obtained from the World Checklist of Vascular Plants dataset received from the Royal Botanic Gardens, Kew in December 2019 (Kew WCVP 2019). In both cases, the import included accepted names and synonyms and each of these taxonomic states was preliminarily assigned to entities that were considered to be part of the Plettkea lineage based on molecular data. With the objective of ensuring that we gathered all names published in our study group, the relevant treatments of South American Caryophyllaceae were also consulted, especially Williams (1898), Mattfeld (1922), Macbride (1936), Zarucchi & Gereau in Brako & Zarucchi (1993) and Beck & al. (2014) for the central Andes. Furthermore, the Catálogo de las plantas vasculares del Cono Sur was considered (Zuloaga & al. 2008) and the recent review by Montesinos-Tubée & Teillier (2022) for Chile. Further names were entered into the TEN's database using the EDIT Platform for Cybertaxonomy (Berendsohn 2010), if not already present. The EDIT Platform is an open-source software with tools and services covering all parts of the taxonomic workflow. Moreover, we cross-checked this data set with Tropicos. org (2023). We then used JSTOR Global Plants (JSTOR 2023) to search for type material associated with the respective names to verify information in the protologues and discover additional type specimens.

Identification of plant material and elaboration of the taxonomic treatment

In the absence of a modern Flora or identification keys, type and other herbarium specimens cited in the original works were examined for a spectrum of morphological characters including those mentioned in the original descriptions to compare with our recently collected material. This process included further specimens of our Andean study group at the cited herbaria to assess the amount of morphological variation and to group the available specimens into morphologically distinct entities including the type specimens. It must be noted that many of the herbarium specimens had so far remained unidentified to species. In a second step, these entities were compared with the specimens included in lineages recovered by molecular phylogenetic analysis in order to check consistency in the presence of morphological character states. In general, in terms of species delimitation the molecular trees are taken as a hypothesis of what the closest relatives of a species are, and thus the differences in morphology these taxa will be discussed (in the notes of the taxonomic treatment). Also, the geographic location of the type specimens was checked in order to see if these localities were included within a hypothesized range of a respective taxon at species level. Due to the often very small number of specimens available for the respective entities, we did not employ any morphometric approach.

Assessment of morphological characters

Habit characters were mostly examined during fieldwork and recorded for the collected specimens. All other characters were assessed from herbarium specimens with Olympus SZX10 and NSZ-405 1X-4.5X stereo microscopes. For new to be described species, macro photos were taken in addition to the text description. The colour of the distinct organs was assessed with a colour chart. Seed morphology was evaluated under a Hitachi FE-SEM (Field Emission Scanning Electron Microscope) at BGBM. Furthermore, field photographs of the collected and analysed specimens were taken. In Fig. 1 the cushion type habits of species belonging to the Plettkea clade is shown. Fig. 2 depicts living specimens of species of the ‘Petiolares’ clade of Stellaria from Peru.

DNA extraction, PCR amplification and sequencing

Genomic DNA was isolated from silica-gel dried or herbarium materials using the triple extraction Cetyltrimethylammonium bromide (CTAB) procedure by Borsch & al. (2003).

The chloroplast trnL-F region was amplified with universal primers trnTc and trnTf (Taberlet & al. 1991). Reaction conditions entailed 5.0 ul of 10X Taq Reaction Buffer, 3.0 ul of 25 mM MgCl2, 5.0 ul of 5 M betaine, 2.0 ul of 10 pm/ul of the forward and reverse primer, 6.25 ul of dNTP (each 1.25 mM) and 0.25 ul Hot Start Taq polymerase made up to a total of 50 ul with ultrapure water. The following temperature and timing were applied for the PCR amplifications: denaturation at 95 °C for 2 min; 30 cycles consisting of 94 °C for 30 s, 52–54 °C for 30 s, 72 °C for 90 s; and 72 °C for 10 min; 4 °C hold. Due to microsatellites, primers trnL460F (Worberg & al. 2007) and trnTd (Taberlet & al. 1991) were employed as additional sequencing primers. For matK we amplified the whole region spanning the trnK 5′ exon to the psbA gene, thus covering the trnK group II intron, the matK CDS and the trnK-psbA spacer. This region was generally amplified in two halves using primers trnKF + CARYmatK1440R (upstream) and CARmatK480F + psbA5R (Steele and Vilgalys 1994). For degraded DNAs from herbarium samples, the region was amplified in quarters using primer pairs trnKF + CARmatK978R (5′-TTT GGT TAG AAW AAT TAG CCG-3′; designed here), CARmatK745F (5′-CTA TCC ACT TAT CTT TCA GG-3′; designed here) + CARYmatK1440R (Schäferhoff & al. 2009), CARmatK480F (GBOL Project, T. Borsch, pers. comm.) + CARmatK910R (5′-AAT GAC TGC AAA TCC TTC TGA-3′; designed here), and CARmatK1040F (5′-AGT CAA ATG TTA GAA AAT GC-3′; designed here) + psbA5R. Due to several mismatches that prevented amplification the new primer CARmatK1033F (5′-GGTACGGAGTCAAATGTTAG-3′) was designed for Stellaria radians to replace CARmatK1040F. Most of these primers were also used for sequencing. CARmatK537R (5′-TTTAGATTATTCCAATTATG-3′) was designed as an additional specific sequencing primer to fill gaps between long microsatellites in some species. The nrITS region was generally amplified with the universal primers ITS4 and ITS5 (White & al. 1990). Since this led to the amplification of fungal DNA in a number of samples, the Caryophyllaceae-specific primer CARITS5 (5′-AGGATCATTGYCGAAACCTG-3′) was designed to replace ITS5 in these cases. PCR products were then run over a long gel and excised to remove unspecific fragments and purified over a GenepHlow™ Gel/PCR Kit from geneaid (article no. DFH300). Concentrations were measured using the Nanodrop – Spectrophotometer nd-1000-v3.7. Cycle sequencing was then carried out by Macrogen Europe in Amsterdam (the Netherlands) with the BigDye® Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems) on an ABI 3730xl DNA Analyzer (96-capillary sequencer).

Multiple sequence alignment, indel coding and tree inference

Pherograms were assembled with PhyDE 0.9971 (Müller & al. 2010) and errors in base calling, which occurred as a slippage effect in particular after long microsatellites, were corrected manually. Multiple sequence alignment followed a motif approach to recognize microstructural mutational events including one to several nucleotides at once (Kelchner 2000; Morrison 2009) following the alignment rules as laid out in Löhne & Borsch (2005). Simple indel coding (Simmons & Ochoterena 2000) was done through SeqState (Müller 2005). Maximum parsimony was implemented in PAUP* version 4.0a169 (Swofford 2002) using random addition with 1000 replicates, TBR Branch swapping an MULTREES in effect. PAUP* was also used for Jackknifing with 36.788 % of characters deleted in each of 10,000 replicates. The program jModeltest 2.1.10 (Darriba & al. 2012) was used to determine the best-fitting evolutionary models using the Akaike Information criterion to select them. For the trnK intron and trnK-psbA spacer as well as the trnL-F region TIM1+G were found, for the matK CDS the TVM+G model and for ITS (SYM+I+G). Bayesian trees were inferred with MrBayes v. 3.2 (Ronquist & al. 2012), implementing four independent runs with four chains each and 5 million MCMC generations. Convergence and effective sample size (ESS) were checked with Tracer v. 1.7 (Rambaut & al. 2018). The burn-in was set at 2500 and every 1000^th generation was sampled to calculate a majority rule consensus tree. The detailed specifications in the MrBayes block can be seen in the matrices provided for the plastid and ITS partitions (see results). Maximum Likelihood calculations were done with RAxML v.8.2.12 on XSEDE in CIPRES using the GTR model for substitutions and the BIN model for indel characters. TreeGraph 2.15.0-887 beta (Stöver & Müller 2010) was used to visualize and annotate the trees based on the Bayesian majority rule consensus, and depicting confidence values for nodes from all three tree inference methods. Scleranthus annuus L. was selected to root the trees to a relatively distant taxon outside the Alsineae and Arenarieae tribes as its putative sister (Arabi & al. 2022). This way, the circumscription of Stellaria proposed by Sharples & Tripp (2019) could be further tested with sequence data and an extended taxon sampling including many species hitherto not represented in any phylogenetic analysis.

Fig. 1

(p. 120). Habit in natural environment of some species of the Plettkea clade of Stellaria. – A: S. alpamarcae, Huánuco, Huamalies, 4400 m (Montesinos 5487, CAR440); B: S. congesta, Huánuco, Huamalies, 4200 m (Montesinos 4900, CAR661); C: S. galianoi, Cusco, Urubamba, near Malaga pass, 4240 m, shady rocky slopes in moist grasslands (Montesinos & von Mering 4523, CAR677); D: S. macbridei, Huánuco, Lauricocha, 4790 m (Montesinos 4590, CAR630); E: S. pedunculosa, Moquegua, near Ticsani volcano, 4818 m, pumice slopes (Montesinos & Chicalla 5395d, CAR777); F: S. utcubambensis, Amazonas, Chachapoyas, Leymebamba, Tajopampa, 3700 m, rocky summits of recently burnt slopes (Montesinos & Garcia 4979, CAR433); G: S. weberbaueri, Arequipa, 4876 m, forming cushions with eventually elongated stems (Montesinos & von Mering 4496, CAR670); H: S. xanthophylla Amazonas, S Leymebamba, 3540 m, forming dense mats (Montesinos 6970a, CAR691). – All photographs by Daniel B. Montesinos-Tubée.

Sequence data sets

The plastid data set contained 51 samples. The trnL-F and trnK-matK sequences of 49 samples (all 23 from the Plettkea clade) were generated in this investigation and two (DB38206 Rabelera holostea (L.) M. T. Sharples & E. A. Tripp and DB38311 Stellaria cf. alsine Grimm) were taken from the German Barcode of Life (GBOL) project. The multiple sequence alignment of the trnL-F region contained 1345 positions, from which the first 32 and the last 36 were trimmed ( Supplementary appendix S1 (wi.53.53301_Supplementary_appendix_S01_trnK-matK-psbA_trnL-F_annotated.pde)). Seven short mutational hotspots were excluded because of poly-AT microsatellites (poly GC in pos. 1256–1267 in Arenaria) and a part of the trnL p8 loop (pos. 364–455) constituted by a long polyA/T satellite and AT-rich elements for which no homology could be assessed between the Stellaria clade (including Plettkea) and the other lineages. The trnL-F region contributed 1105 characters to the final matrix of which 420 (34.9 %) were variable and 220 (18.3 %) were informative, plus 99 indel characters of which 37 were informative. The multiple sequence alignment of the trnK-matK partition ( Supplementary appendix S1 (wi.53.53301_Supplementary_appendix_S01_trnK-matK-psbA_trnL-F_annotated.pde)) had a length of 3124 positions, comprising the complete trnK intron with the matK CDS, the trnK 3′ exon, the trnK-psbA intergenic spacer and 40 nucleotides of the psbA gene. Ten short mutational hotspots (mostly microsatellites and regions comprising short AT-rich repetitive elements without clear homology) were excluded from the trnK intron partition. The matK-trnK region contributed 2935 characters, of which 1086 (37 %) were variable and 535 (18.2 %) informative. The indel partition contributed 117 of these characters from which 38 were informative. The complete combined plastid matrix used for analyses is provided in  Supplementary appendix S2 (wi.53.53301_Supplementary_appendix_S02_combined_cp_matrix_sic_MrBayes.nex).

The ITS dataset included 49 sequences, from which 47 were generated in this study and 2 were obtained from the GBOL project to complement the ITS partition for the same samples. The alignment contained 802 nucleotide positions ( Supplementary appendix S3 (wi.53.53301_Supplementary_appendix_S03_ITS.pde)), all of which were used in the matrix for tree inference. Simple indel coding resulted in additional 78 binary characters ( Supplementary appendix S4 (wi.53.53301_Supplementary_appendix_S04_ITS_matrix_sic_MrBayes.nex)).

Trees inferred from the plastid partition

The Bayesian majority rule consensus tree is shown in Fig. 3 and depicts a well resolved and statistically supported backbone of the Alsineae. Three sublineages (A, B, C) are found within a Plettkea clade, although these three and sublineages defined by two other species (Stellaria galianoi Montesinos & Borsch, S. macbridei Montesinos & Borsch) remain in a polytomy. An identical picture is given by the maximum parsimony strict consensus tree summarized from 5780 shortest trees with a score of 2267 ( Supplementary appendix S5 (wi.53.53301_Supplementary_appendix_S05_plastid_MP-ML_tree.pdf)). The ML tree with the best likelihood score ( Supplementary appendix S5 (wi.53.53301_Supplementary_appendix_S05_plastid_MP-ML_tree.pdf)) shows these species in inconsistent, unsupported positions as sisters to subclades C and A, respectively. The sample representing the ‘Nitentes’ clade (DB38311) is found with high support as sister to the Plettkea clade by all tree inference methods (Fig. 3). A further exploratory tree with the sequences available from GenBank of S. cryptantha (Mattf.) M. T. Sharples & E. A. Tripp (trnL-F and partial matK) and several species of the other major Stellaria clades (c. 800 nt fragments of matK) can also be found in  Supplementary appendix S6 (wi.53.53301_Supplementary_appendix_S06_plastid_tree_with_sequences_from_GenBank.pdf) (and matrix in  S7 (wi.53.53301_Supplementary_appendix_S07_plastid_matrix_with_sequences_from_GenBank.nex)).

Trees inferred from nrITS

The ITS Bayesian majority rule tree (Fig. 4) provides slightly more resolution within a well-supported Plettkea clade with sublineage B plus Stellaria utcubambensis Montesinos & Borsch (CAR433) and sublineage C being sisters, although not very well supported. The lineage with the two samples of S. galianoi then appears as sister to this clade albeit with significant support (0.98 PP) for the respective node only by Bayesian inference. The respective positions of the representatives of the ‘Larbreae’ (S. pungens Brongn., S. ruscifolia D. F. K. Schltdl.) and ‘Nitentes’ clades sensu Sharples & Tripp (2019) differ inconsistently between the Bayesian and the ML tree ( Supplementary appendix S8 (wi.53.53301_Supplementary_appendix_S08_ITS_MP-ML_tree.pdf)) while the first branching position of the ‘Petiolares’ followed by the ‘Insignes’ clade is congruently found in both, although not very well supported by Bayesian PP or Likelihood BS. An exploratory analysis with available published ITS sequences with a much better sampling of the ‘Larbreae’ and ‘Nitentes’ clades ( Supplementary appendix S9 (wi.53.53301_Supplementary_appendix_S09_ITS_tree_with_sequences_from_GenBank.pdf) and matrix in  S10 (wi.53.53301_Supplementary_appendix_S10_ITS_matrix_with_sequences_from_GenBank.nex)) shows both in a sister group relationship with high support, contrary to the ITS tree in Fig. 4. Nevertheless, the first branching position of the ‘Petiolares’ clade in Stellaria remains unaffected by taxon sampling (Fig. 4,  Supplementary appendix S9 (wi.53.53301_Supplementary_appendix_S09_ITS_tree_with_sequences_from_GenBank.pdf)).

Overall relationships in Stellaria and position of the Plettkea clade

In comparison with previous phylogenetic analyses of Plettkea that were only represented by two species, one in the RAD study by Sharples & Tripp (2021), and another in the tree of Caryophyllaceae by Greenberg & Donoghue (2011) we could include 14 of the 20 species of the Plettkea lineage into a phylogenetic analysis of both plastid and nrITS regions (Fig. 3, 4) which resulted in a maximally supported clade throughout all analyses that was recovered as deeply nested within the monophyletic genus Stellaria according to the circumscription of Sharples & Tripp (2019). An additional species of the Plettkea clade, S. laevis (Bartl.) Rohrb. (AC912) was recovered with ITS ( Supplementary appendix S9 (wi.53.53301_Supplementary_appendix_S09_ITS_tree_with_sequences_from_GenBank.pdf)) within the Plettkea clade. The RAD trees of Stellaria presented by Sharples & Tripp (2019), depicted five major clades. The only specimen from the Plettkea clade represented therein is S. tetrasticha (Mattf.) M. T. Sharples & E. A. Tripp, annotated by the authors as “Plettkeae”. It appeared as sister to the ‘Larbreae’ and ‘Nitentes’ clades, whereas the ‘Insignes’ clade (represented by S. radians L., S. pubera Michx. and S. sessiliflora Y. Yabe) was found sister to the ‘Petiolares’ clade.

The relationships of the species-rich ‘Larbreae' clade (Sharples & Tripp 2019) to the ‘Nitentes’ clade and the Plettkea clade remain unclear. Whereas our plastid topology provides a well-supported hypothesis of the ‘Nitentes’ being sister to the Andean Plettkea clade, ITS seems to favour a sister group relationship of the ‘Larbreae’ and ‘Nitentes’, also shown by the best-scoring ML tree of the RAD data in Sharples & Tripp (2019). Future phylogenomic analyses using hybseq data should be employed to test for a possible reticulate event that could have occurred before the divergence of the Plettkea crown group in the Andes. The more broadly sampled ITS tree ( Supplementary appendix S9 (wi.53.53301_Supplementary_appendix_S09_ITS_tree_with_sequences_from_GenBank.pdf)) indicates that Stellaria alsine as currently accepted contains at least two different evolutionary lineages, while further samples with this annotation in GenBank rather seem to be misidentified (in the ‘Petiolares’ clade). Sharples (2023) proposed in a short paper that appeared during the revision of this manuscript, that the name S. undulata Thunb. (≡ S. alsine var. undulata (Thunb.) Ohwi) would apply to the lineage of specimens resolved in the ‘Larbreae' clade, so that the specimens shown in our Fig. 3 and 4 in the ‘Nitentes’ clade are true S. alsine. Nevertheless, a detailed analysis of species limits and distribution of this entity is still lacking. A further question arises regarding the phylogenetic position of the ‘Petiolares’ clade which also contains a significant number of South American species of Stellaria (e.g. S. cuspidata Willd. ex D. F. K. Schltdl., S. recurvata Willd. ex D. F. K. Schltdl., S. sp., S. weddellii Pedersen; Fig. 3, 4) and which may constitute another south American radiation within Stellaria. Whereas ITS data indicate a first branching position of the ‘Petiolares’ clade, the analyses of RAD data by Sharples & Tripp (2019) yielded different results depending on the selection of loci and the genetic distances covered by the taxon set. Their analysis based on more loci showed a tree incongruent to our ITS phylogenies (Fig. 4,  Supplementary appendix S9 (wi.53.53301_Supplementary_appendix_S09_ITS_tree_with_sequences_from_GenBank.pdf)). Also, our plastid trees are different, providing evidence for a possible paraphyly of the ‘Petiolares’ clade with respect to S. radians (‘Insignes’ clade). However, a detailed plastid phylogenomic analysis needs to be undertaken to recover the true history of the plastid genome as the current plastid sequences may not provide a sufficient character sampling of this genomic compartment to properly recover the respective nodes. The sister group relationship of the ‘Petiolares’ and ‘Insignes’ lineages in the ITS tree (Fig. 3) is supported only through Bayesian posterior probabilities but not by ML-BS and MP-JK and thus depends on the inference method.

Composition and species-level relationships within the Plettkea clade

The Plettkea clade gains maximum support in all trees (Bayesian Inference, Maximum Parsimony, Maximum Likelihood inferred from plastid and nuclear partitions) and appears as a crown group on a rather long internal branch within Stellaria, suggesting that it forms an Andean radiation within this genus. In our trees the clade contains 13 taxa (represented by 23 samples). Considering that this is the first thorough sampling of this Andean plant group, and that so far, no comprehensive taxonomic revision existed, several entities turned out to represent new species, and changes are required in nomenclature. These are presented in the taxonomic treatment section (below). For simplicity and better readability, we already use the correct names here in the discussion and to annotate species in the phylogenetic trees. Fig. 3 and 4 include colour bars for species previously recognized under Arenaria and under Pycnophyllopsis (sensu Timaná 2017). This includes the two former species of Pycnophyllopsis that Sharples & Tripp (2019) already merged with Stellaria (S. cryptantha (Mattf.) M. T. Sharples & E. A. Tripp and S. tetrasticha (Mattf.) M. T. Sharples & E. A. Tripp) based on RAD data of S. tetrasticha.

Fig. 2.

Representatives of the ‘Petiolares’ clade. – A: Stellaria cuspidata, S Peru, Arequipa, Chiguata, 3300 m; B: Stellaria sp., central Peru, Huánuco, Huamalies, 3200 m; C: S. recurvata, N Peru, Amazonas, 3200 m; D: S. weddellii, S Peru, Cusco, Urubamba, 4200 m, forming clumps, growing together with Aciachne pulvinata Benth. (Poaceae). – All photographs by Daniel B. Montesinos-Tubée.

The trees inferred from plastid and nrITS sequence data are largely congruent and depict three sublineages (A, B, C) in addition to branches representing three more isolated species (Stellaria galianoi, S. utcubambensis, S. macbridei, respectively). According to Timaná (2017) eight species were classified as Pycnophyllopsis, all of which belong to the Plettkea clade as part of the genus Stellaria (Fig. 3, 4). The first is P. muscosa Skottsb., which is the type species of the genus Pycnophyllopsis and is considered to stand out by a “stellate calyx rather than the typical oblong, nearly cylindrical oblong calyx that characterizes all the other species in this genus [Pycnophyllopsis]” (Timaná 2017). then P. keraiopetala Mattf., P. cryptantha (Mattf.) Molinari, P. laevis (Bartl.) Timaná, P. macrophylla (Muschl.) Molinari, P. smithii Timaná, P. tetrasticha (Mattf.) Timaná and P. weberbaueri (Muschl.) Timaná. According to our molecular trees, the genus Pycnophyllopsis would therefore be polyphyletic within the Plettkea clade, considering that P. keraiopetala and P. weberbaueri belong to sublineage C and P. cryptantha and S. laevis to sublineage A (Fig. 3, 4 and  Supplementary appendices S6 (wi.53.53301_Supplementary_appendix_S06_plastid_tree_with_sequences_from_GenBank.pdf) and  S9 (wi.53.53301_Supplementary_appendix_S09_ITS_tree_with_sequences_from_GenBank.pdf)).

Sublineage A in the plastid tree comprises the two individuals of Stellaria alpamarcae (CAR439 and CAR440) in a tritomy together with the only sample of S. engleriana (Muschl.) Montesinos & Borsch (CAR632). The plastid sequence of S. xanthophylla Montesinos & Borsch represented by the single specimen is depicted as sister with 1.0 BI-PP and 83.3 % MP-JK whereas ITS does not resolve relationships among these individuals [CAR429 = S. spinulosa Montesinos & Borsch is inconsistently depicted as part of a polytomy with a general score of 64.3 % to which CAR439 does not belong]. The plastid data set further resolves the two specimens of S. congesta Montesinos & Borsch as sisters in the plastid tree that are also just depicted within the broad polytomy of the core of sublineage A with ITS. Stellaria cryptantha (CAR431) is congruently resolved as sister to the other members of the sublineage by the plastid and nuclear genomic partition, and with high support (Fig. 3, 4). This sublineage A is characterized for its occurrence in central Peru, the plants form mats, leaves and sepals with true spine-like apical portions rather than the usual compact or sprawling forms found in the sister sublineage B which also occur in S Peru and NW Bolivia.

Fig. 3.

Bayesian majority rule consensus tree inferred from combined trnK-matK-psbA + trnL-F sequence matrix including indels. Posterior probabilities are above branches, parsimony jackknife values are below branches left and in italics, and maximum likelihood bootstrap percentages right and in bold. The monophyletic Stellaria sect. Plettkea is deeply nested within the genus Stellaria. Species previously classified within Arenaria and Pycnophyllopsis are annotated with a red or green bar, respectively.

Sublineage B is found in all trees and comprise Stellaria andina (Rohrb.) Montesinos & Borsch and relatives. This species is best represented in our molecular analysis with three samples from Bolivia (CAR377, B101149337; CAR634, B101149331; CAR638, B101149337) and one sample from Peru (CAR664, B100745260). These form a well-supported clade (1.0 BI-PP and 100 % MP-JK) in which a single sequence from Peru appears as sister to the three sequences from Bolivia (0.82 BI-PP and 51.1 % MP-JK in the plastid tree and this is congruently found in the ITS tree (86.6 % MP-JK and 59.3 MP-JK, respectively). All four specimens share the glabrous, petiolate leaves and the subglobose calyx, and occur in similar habitats, indicating that the molecular differences show a pattern of phytogeographic differentiation within this species. Although node support is not very high, S. pedunculosa (Wedd.) Montesinos & Borsch is congruently inferred as sister to the S. andina clade with both genomic compartments. Stellaria apurimacensis Montesinos & D. Cornejo constitutes the earliest branch of subclade B, consistently in both the plastid and nuclear trees. The species is represented here by one specimen (CAR619) that is the type. Whereas our molecular data provide confidence for the position of S. apurimacensis in subclade B (1.0 BI-PP and 99.7 MP-JK in matK-trnK-psbA + trnL-F and 89.2 MP-JK in ITS) the support for the clade comprising S. andina and S. pedunculosa is rather low and appears to be connected to its short internal branch. Nevertheless, considering that these two other species of subclade B appear to be clearly monophyletic, our phylogenetic results underscore the status of S. apurimacensis as a distinct species.

Fig. 4.

Bayesian majority rule consensus tree inferred from nuclear ribosomal (ITS) sequence matrix including indels. DNA posterior probabilities are above branches, parsimony jackknife values are below branches left and in italics, and maximum likelihood bootstrap percentages right and in bold. The monophyletic Stellaria sect. Plettkea is deeply nested within the genus Stellaria. Species previously classified within Arenaria and Pycnophyllopsis are annotated with a red or green bar, respectively.

Sublineage C (Fig. 3, 4) is constituted by samples of two species previously classified as Pycnophyllopsis. These are Stellaria keraiopetala (Mattf.) Montesinos & Borsch (one specimen CAR639, B101149336) sister to the lineage of the two sequenced specimens of S. weberbaueri (Muschl.) Montesinos & Borsch (1.0 BI-PP and 99.9 % of MP-JK in the plastid tree and 87.9 in MP-JK with ITS. The ITS tree depicts maximum support for subclade C (100 % MP-JK) whereas the branch leading to the respective node in the plastid tree is rather short (0.54 BI-PP, 52.8 MP-JK). Sublineage C entails two morphologically rather different species. Apart from the deviating dioecious reproductive system in S. weberbaueri (Timaná 2017), S. keraiopetala differs by a reduced stamen number. In terms of habit as seen in the field, both species, however, appear to be very similar and resemble cushion-forming species of Pycnophyllum. In terms of the taxon concepts at species level we agree with Timaná (2017) who accepted Pycnophyllopsis keraiopetala as different from P. weberbaueri. The latter of which is sampled by two individuals (CAR653 and CAR670) that appear as sisters.

The plastid tree recovered three entities in an unresolved position within the Plettkea clade that do not belong to any of the three subclades (A, B, C); this is corroborated by ITS. Stellaria macbridei (a new name for Arenaria crassipes) is the first of these and represented by two sequences in our trees [CAR430 (B100766225) and CAR630 (B100761527)] that form a well-supported clade with 1.00 BI-PP and 98.3 % MP-JK (plastid tree) and 99.9 % MP-JK in the ITS tree. Both sequences were obtained from two isolated populations near the boundary of the Huánuco-Áncash departments, in highland slopes. These plants are characterized by having subcoriaceous or membranous leaves with a hirsute midrib, a character not found in the other species of the clade. The second isolated entity is S. galianoi. The sequences represent the species based on two collections, one of which is the type of the species (CAR438), in a lineage supported by 1.0 BI-PP and 99.5 % MP-JK. Whereas the plastid tree does not allow any conclusions on its relationships with the Plettkea clade, the ITS tree suggests it is sister to subclades B plus C. Stellaria galianoi is characterized by its flexible stems and leaves, long internodes and shady habit, and considered as a unique taxon in the clade for having longer internodes than all other species of the Plettkea clade. The third of these more isolated entities is S. utcubambensis, newly discovered here and is based on a single specimen from the Amazonas department in N Peru [CAR433 (B100766222)]. The ITS tree indicates a sister-group relationship of S. utcubambensis to subclade B. This species is unique in the clade since it is the easternmost distributed in the Andes in an isolated canyon that is formed by the Utcubamba river, which leads to the Amazonas in N Peru.

Fig. 5.

SEM images of seeds of Stellaria species described as new species – A, B: S. apurimacensis; C, D: S. galianoi; E, F: S. utcubambensis; G, H: S. xanthophylla. – Scale bars: A, C, E, G = 0.5 mm; B, D, F, H = 50 µm.

Biogeography of the Plettkea clade

Stellaria sect. Plettkea (Mattf.) Montesinos & Borsch represents another radiation of angiosperms at mostly high altitudes in the central Andes. This investigation revealed the existence of a clade of some twenty species that are distributed in the region. Similar examples of central Andean radiations can be found in other genera such as Lupinus (Fabaceae; Hughes & Eastwood 2006), which more recently were shown to consist of geographically structured sub-radiations along the Andes (Contreras-Ortiz & al. 2018) or Gomphrena (Amaranthaceae; Ortuño Limarino & Borsch 2020).

All of these radiations are relatively young, starting 1.5–2 mya in Lupinus (Hughes & Eastwood 2006) or 3.5–4 mya as in Gomphrena (Ortuño Limarino & Borsch 2020). Whereas the Andean clade of Gomphrena has two sublineages, one in central Bolivia and S Peru and the other in central to south Bolivia and northern Argentina, species diversification in the Plettkea clade to some extent seems to reflect the biogeographic subdivision of the Amotape-Huancabamba zone (Weigend 2004) in Peru. Stellaria sect. Plettkea subclade A (Stellaria alpamarcae, S. congesta and relatives) occurs in the northern half of Peru (from the departments of Lima and Junín northward) whereas subclades B and C (Fig. 3, 4) seem to be confined to areas further southeast of the Amotape-Huancabamba zone, reaching into Bolivia. It will be interesting to further test if an early branching position of S. galianoi (from department of Cusco in the southwestern part of the distribution of the Plettkea clade) in subclade B as suggested by the ITS tree (Fig. 4) will be substantiated by adding further molecular characters. The Plettkea clade will therefore be an interesting study group to better understand the biogeographical patterns in the central Andes. It is to be hoped that the key provided in our study will help to discover further specimens of S. sect. Plettkea for an improved mapping of species distributions.

Taxonomic treatment

Stellaria sect. Plettkea (Mattf.) Montesinos & Borsch, comb. & stat. nov. ≡ Plettkea Mattf. in Schriften Vereins Naturk. Unterweser, n.s., 7: reprint p. 13 (11, 17). 1934. – Type: Stellaria cryptantha (Mattf.) M. T. Sharples & E. A. Tripp (≡ Plettkea cryptantha Mattf.).

= Baretia Timaná in Adansonia, ser. 3, 45: 502. 2023, syn. nov. – Type: Baretia lanata (Phil.) Timaná (≡ Pycnophyllum lanatum Phil.).

Morphological description — Annuals or perennials, mostly prostrate, cushion-forming or mat-like, sometimes in small and dense tufts. Stems often decumbent, rarely ascending, 2–60 cm high (Stellaria galianoi having greatest height), stems glabrous with few exceptions (S. apurimacensis) specially at nodes of leaves where hirsute hairs may occur, often glandular in surface; internodes hirsute or glabrous, short as in most of species and longer in S. apurimacensis and S. galianoi. Leaves mostly ovate, but linear to lanceolate in some species, 2–10 mm long, with acute or mucronate apex, usually hirsute near base, margins glabrous or ciliate, rarely lanuginose. Flowers solitary, only terminal, or in some species also axillary on short peduncles, with 5 sepals, free to base, mostly ovate to lanceolate, acute to acuminate in apex, base hirsute and stiff in texture, 1.8–5 mm long; petals mostly 5, rarely 4 or 3, showy and white or cream in colour and then usually bifid at apex, 10–15 mm long, or reduced to various degrees, mostly obtuse at apex, cream to translucent, and only up to 5 mm long and not overtopping sepals; stamens 5, often adherent to petals, filaments filiform and terete throughout (in all species for which descriptions are provided here), rarely thickened at base (P. keraiopetala, P. patagonica), in dioecious species sometimes a few staminodes present in pistillate flowers; ovary ovoid to globose, with trifid or rarely bifid styles, very rarely style single and unbranched (S. villasenori), in dioecious species often rudimentary pistillodes present in staminate flowers, these not more than 1 mm long and seedless. Capsule 1–12-seeded; seeds more or less conspicuously tuberculate.

Notes — Until now there was no formal infrageneric name for the Plettkea clade. Sharples & Tripp (2019) annotated the lineage of Stellaria tetrasticha, corresponding to the Plettkea clade, in their trees with “Plettkeae” albeit without any reasoning for that name. The first infrageneric classification system by Fenzl (1840) recognized four entities, one of which, “Eustellaria”, was further subdivided. However, no specific nomenclatural rank was designated, until Pax & Hoffmann (1934) specified these entities as sections and subsections, respectively. We therefore suggest continuing the use of the sectional rank for the subdivision of Stellaria. No entity corresponding to a section Plettkea was included by Fenzl (1840) or Pax & Hoffmann (1934), so it is described here as a section of Stellaria.

As Sharples (2019) and Sharples & Tripp (2019) already pointed out, more work needs to be done to develop a consistent infrageneric classification for Stellaria, which includes testing if existing sectional/subsectional names are validly published. Considering that S. graminea was designated as the neotype for the monophyletic genus Stellaria (Tikhomirov 2016), and that the name “Eustellaria” is not permitted under Art. 21.3 of the Code (Turland & al. 2018), the ‘Larbreae’ clade (sensu Sharples & Tripp 2019) would become the typical S. sect. Stellaria (Sharples & Tripp 2019;  Supplementary appendix S9 (wi.53.53301_Supplementary_appendix_S09_ITS_tree_with_sequences_from_GenBank.pdf)).

Pax & Hoffmann (1934) validated the rank of Arenaria sect. Dicranilla (Fenzl) Pax & K. Hoffm. that was originally described by Fenzl (1840) based on A. dicranoides Kunth and A. bryoides, both described based on material from Mexico. In their treatment, Pax & Hoffmann (1934) also extended the concept of this section to include Andean species like A. bisulca (Bartl.) Fenzl & Rohrb., A. pycnophylloides Pax, A. alpamarcae A. Gray, A. boliviana F. N. Williams, A. pedunculosa Wedd., and A. pycnophylla Rohrb. However, the authors overlooked that these species do not match the original diagnosis by Fenzl (1840), who stated that the species of Dicranilla (Fenzl) Rchb. possess smooth, shiny, black seeds. On the contrary, members of the Andean Plettkea clade have tuberculate, brown seeds. Molecular phylogenetic data (T. Borsch, unpublished) further show that A. dicranoides belongs to the core Arenaria clade, underscoring that Pax & Hoffmann (1934) created an extended, morphologically heterogeneous and polyphyletic section. McNeill (1962) typified the genus name Dicranilla based on the section with Arenaria dicranoides, and commented on the misinterpretation of the seed characters by Pax & Hoffmann (1934). In summary, there was no name available for the ‘Plettkea’ clade at the level of section.

The publication by Timaná (2023), describing the new genus Baretia based on Pycnophyllum lanatum (Stellaria villasenorii), was received while correcting the proofs of this paper. We treat Baretia as a synonym here because to accept the new genus would make Stellaria paraphyletic.

Key to the species of Stellaria sect. Plettkea

Species-level taxonomic backbone and descriptions

1. Stellaria alpamarcae (A. Gray) Montesinos & Borsch, comb. nov. ≡ Arenaria alpamarcae A. Gray, U.S. Expl. Exped., Phan. 15: 116. 1854. – Lectotype (designated here): Peru, 1838–1842, Wilkes Expedition s.n. (GH00037630 image!; isolectotype: NY00342438 image!). – Fig. 1A.

Morphological description — Perennial herb, caespitose forming pulvinate dwarf cushions 2–4 cm high and 8–20 cm in diam.; root woody. Stems short or elongated erect in young plants becoming decumbent later on, usually covered by old foliage; internodes 1–2 mm long, with a scarce indumentum of trichomes < 0.1 mm. Leaves imbricate, lamina ovate-lanceolate, 4–7 mm long and 0.9–1.2 mm wide, longitudinally striate, midrib prominent on underside, margins thick, delicately folded toward adaxial surface, glabrous in distal part and at acuminate apex, turning ciliate toward base, where hairs can be dense (1–3 mm long). Plants bisexual-hermaphrodite. Flowers on 2–6 mm long, glabrous peduncles, terminal and axillary; perigynous, oblong, c. 4.5 mm long and 1.5–2.5 mm wide; calyx cylindrical-oblong; sepals 5, imbricate, oblong, 3–4 mm long and 1–2 mm wide, smooth, glabrous on surface and margins, apex acute-acuminate, usually folded and forming a cone-like cylinder that covers capsule; petals 5, strongly reduced, translucent, ovate, apex obtuse, c. 0.8 mm long and 0.5 mm wide; stamens 4 or 5, episepalous, 0.8–1.1 mm long; ovary cylindrical-turbinate, 0.6–0.9 mm long and 0.4–0.6 mm wide, style 3-fid, stigma aciculate, terete. Capsule ovoid, c. 1.5 mm long, containing 5–8 seeds, these globular in shape, c. 0.2 mm wide and 0.3 mm long; testa pale brown and cells with whitish stellate tubercles.

Distribution and ecology — Stellaria alpamarcae is endemic to Peru (Cano & Sánchez 2006), occurring in Áncash, Huancavelica, Huánuco, Junín and Lima departments, at altitudes of 4000–4700 m. The species occurs in Puna grasslands distributed in highland passes, which are relatively humid throughout the year.

Notes — The specimen chosen as the lectotype was likely examined by Asa Gray for the description of the species. Assuming it came from the same gathering, the specimen in NY (NY00342438) with a label indicating the years 1838–1842 and “Peru” would be an isolectotype.

The identity of further historical material annotated as isotypes of Arenaria alpamarcae available through JSTOR Global Plants (JSTOR 2023) is less clear. The locality information on a specimen in US (US00103277) given as “Alpamarca above Obrajillo and Banos [possibly Baños]” corresponds to the highlands of the Lima department in central Peru, which is possibly a different place. A second specimen in NY (NY00342437) lacks collector and geographical information and a specimen in P (P00335842) has just a label indicating the years 1838–1842 but lacks any collector or locality data beyond “Peru”.

2. Stellaria andina (Rohrb.) Montesinos & Borsch, comb. nov. ≡ Arenaria andina Rohrb. in Linnaea 37: 255. 1872. – Lectotype (designated here): Bolivia, Prov. Larecaja, viciniis Quiabaya via ad Tacacoma, 20 May 1860, G. Mandon 954 (K000471618 image!; isolectotypes: F0053255 image!, P00335843 image!, P00335844 image!, P00335845 image!, P01902983 image!, S-R-351).

Morphological description — Annual herb, sometimes forming large mats or carpets, 5–8 cm high and up to 30 cm in diam.; roots fibrous. Stems erect or decumbent, diffuse, usually loose, internodes 4–6 mm long, glabrous. Leaves opposite, lamina ovate, 2.5–3.5 mm long and 1–1.5 mm wide, surface glabrous on both sides, bright green to yellowish with age, margins bearing c. 0.1 mm long trichomes, midrib imposed on adaxial side, base petiolate and hirsute, apex acuminate. Plants bisexual-hermaphrodite. Flowers on short 1–4 mm long glabrous peduncles, terminal; perigynous, campanulate to subglobose, 4–5 mm long and wide, crateriform,; sepals 5, imbricate, oblong, slightly involute, apex obtuse-acute, base attenuate, 3–4 mm long and c. 2 mm wide, bright green to green-yellowish with age, glabrous to rarely covered by thin white trichomes (< 0.1 mm long) at margins; petals 5, ovate, translucent to pale yellowish, rarely whitish, 1–1.8 mm long and 0.5–1 mm wide, apex rounded to obtuse; stamens 5, episepalous, 0.7–1 mm long; ovary ovoid, 0.8–1.1 mm long, style 3-fid, stigma terete to aciculate. Capsule ovoid, c. 2 mm long, containing 4–6 seeds, these ovate, c. 0.3 mm long; testa maroon, tuberculate.

Distribution and ecology — The species is only known to occur in SW Bolivia and SE Peru, inhabiting highland Puna environments and humid grasslands at altitudes of 4600–5100 m.

Vernacular name — Wanupi Tika, given in Quechua language (Zoilita Salazar Patiño, Arequipa, pers. comm.).

Notes — Paul Rohrbach (Berlin) aimed at a taxonomic synthesis of Andean Caryophyllaceae but died at an early age, so Garcke arranged to have his manuscript published in Linnaea. Rohrbach himself wrote (p. 184) “… so bildet die Mandon'sche Sammlung aus Bolivia den Kern des mir von dort vorliegendem Materials. Ich habe dieselbe in ziemlich gleicher Vollständigkeit in drei Herbarien, dem des k.k. botanischen hofkabinets zu Wien, dem De'Candolleschen und dem des Grafen Franqueville gesehen; …” in the protologue, Rohrbach (1872) mentioned “Mandon 954!” but without designating any particular specimen as a type. There is no specimen in W because Mandon material appears to have been lost due to a fire in the Second World War (Heimo Rainer, pers. comm. and as stated in  https://www.nhm-wien.ac.at/en/research/botany/collections/lost_families).

3. Stellaria apurimacensis Montesinos & D. Cornejo, sp. nov. – Fig. 5A, B, 6;  Supplementary appendix S11 (wi.53.53301_Supplementary_appendix_S11_Stellaria_apurimacensis_isotype.jpg). Holotype: Peru, Apurimac, Cotabambas, Haquira, NW of Haquira, 4525 m, 28 Mar 2017, D. Montesinos & D. Cornejo 5194 (HSP [HSP-9443!]; isotypes: B [B 10 0761536!], CUZ!, F!, USM!).

Diagnosis — The new species is distinguishable by its rosette or small mat, ovate leaves, apetalous flowers and short internodes.

Morphological description — Annual herb, densely ramified at base, forming cushions c. 2 cm high and 6–10 cm in diam.; roots fibrous. Stems decumbent or creeping, 4–6 cm long, often densely branched and covered by older leaves in central and lower parts; internodes 4–10 mm long, glabrous. Leaves opposite, petiolate, lamina elliptical-lanceolate, 2–3 mm long and 0.8–1.2 mm wide, sparsely pilose along margin, trichomes 0.1–0.3 mm long, acuminate, plain or curved, thin, slightly involute, glabrous on both sides, midrib protuberant on underside. Plants bisexual-hermaphrodite. Flowers on rigid or slightly curved 2–5 mm long glabrous peduncles, terminal; perigynous, 2.5–3.5 mm long and 1.5–2.2 mm wide, calyx campanulate, glabrous; sepals 5, imbricate, slightly involute, lanceolate-ovate, cupuliform at base, apex acuminate, glabrous, 2–3 mm long and 1–1.5 mm wide, pale green to yellowish; petals 5, translucent, ovate, 0.8–1.2 mm long and 0.4–0.6 mm wide, apex rounded; stamens usually 10, episepalous, filaments 0.3–0.4 mm long; ovary ovoid, 0.4–0.6 mm long and 0.3–0.5 wide; style 3-fid, curved, glandular, 0.3–0.5 mm long. Capsule ovoid, glabrous, c. 2.2 mm long, containing 4–6 seeds, these roundish to ovate, 0.4–0.5 mm long and 0.3–0.4 mm wide; testa pale brown, cells with tuberculate and stellate protuberances of c. 50 µm in diam.

Distribution and ecology — This species occurs in the Apurimac department on the boundary with the Cusco department at altitudes of 3980–4530 m in open grasslands with rocky outcrops in which species such as Stipa ichu Ruiz & Pav. (Poaceae), Senecio adenophyllus Meyen & Walp. and S. algens Wedd. (Asteraceae) occur.

Etymology — The epithet name is allusive to the Apurimac department located in S Peru, the site of the type locality.

Vernacular name — Hatun Yuraq Tika, given in Quechua language (Zoilita Salazar Patiño, Arequipa, pers. comm.).

Notes — Stellaria apurimacensis is morphologically similar to S. galianoi but differs by the internode length (4–10 mm vs. 2–15 mm in S. galianoi), smaller leaves (2–3 mm long and 0.8–1.2 mm wide vs. 3–5 mm long and 1.4–1.8 mm wide in S. galianoi), shorter peduncles (2–5 mm vs. 7–15 mm in S. galianoi), wider sepals (1–1.5 mm vs. 0.8–1 mm in S. galianoi) and smaller seeds (0.4–0.5 mm long vs. 0.6–0.8 mm long in S. galianoi). Stellaria apurimacensis differs from S. macbridei by the longer internodes (4–10 mm vs. 3–4 mm in S. macbridei), smaller leaves (2–3 mm long and 0.8–1.2 mm wide vs. 5–7 mm long and 2–2.5 mm wide in S. macbridei) and from S. utcubambensis by the weaker stems and leaves (vs. robust in S. utcubambensis).

4. Stellaria congesta Montesinos & Borsch, nom. nov. ≡ Cherleria nitida Bartl. in Presl, Reliq. Haenk. 2: 12. 1831 ≡ Arenaria nitida (Bartl.) Rohrb. in Linnaea 37: 249. 1872 [non Stellaria nitida Hook. in Scoresby, J. Voy. North. Whale-Industry: 411. 1823]. – Lectotype (designated here): Peru, Cobradillo [illegible, possibly misspelled as Obrajillo, town located in Canta, Lima], 1821, Haenke s.n. (GOET000573!). – Fig. 1B.

Morphological description — Perennial herb, caespitose, forming cushions or small mats, c. 4 cm high and up to 20 cm in diam.; root woody. Stems procumbent, numerous, forming a densely congested structure, with 6–10 cm long branches; internodes short, c. 0.1 mm long, glabrous. Leaves imbricate dense, rigid, lamina thick, ovate, 4–7 mm long and 1–1.2 mm wide, acute or slightly mucronate at apex, base scarcely attenuated, margins glabrous, also at base, margins involute, midrib prominent on underside. Plants bisexual-hermaphrodite. Flowers on 2.5–3 mm long, glabrous peduncles, terminal and axillary; perigynous, oblong, 3.5–4.5 mm long and 1–1.5 mm wide; calyx cylindrical-turbinate; sepals 5, imbricate, lanceolate, involute, 2–2.5 mm long and 1–2 mm wide, pale green to yellow, glabrous on surface and margins, apex acute-acuminate, folded and forming a cone-like cylinder that covers capsule; petals 5, strongly reduced, translucent, ovate, apex obtuse, 0.8–1 mm long and 0.5–0.7 mm wide; stamens 4 or 5, episepalous, 0.8–1.1 mm long; ovary cylindrical-turbinate, 0.8–1.2 mm long and 0.8–1.1 mm wide, style 3-fid, stigma aciculate. Capsule narrowly ovoid, shorter than calyx when mature, 1.5–2 mm long, opening with 6 valves, containing 6 seeds, these suborbicular, lentiform, 0.2–0.3 mm in diam.; testa pale brown, bearing whitish protuberances.

Fig. 6.

Morphological details of Stellaria apurimacensis – A: ramified stem; B: leaves; C: detail of pilose hairs on leaf margins; D: mature flower with capsule; E: sepals; F: tuberculate seeds. – From Montesinos & Cornejo 5194b. – Scale bars: A = 2 mm; B, D, E = 0.5 mm; C = 100 µm; F = 200 µm.

Distribution — The species is endemic to Peru (Cano & Sánchez 2006) and is known to occur in Áncash, Huánuco, La Libertad and Junín departments according to the material revised and at altitudes of 3900–4500 m.

Etymology — The epithet congesta refers to the uniform and compact growth of the species.

Notes — The specimen at GOET has the annotation “rel. Haenk. II, 12 (cum descriptione)”, which indicates that the specimen may have been used to make a description.

5. Stellaria cryptantha (Mattf.) M. T. Sharples & E. A. Tripp in Syst. Bot. 44: 871. 2019 ≡ Plettkea cryptantha Mattf. in Schriften Vereins Naturk. Unterweser, n.s., 7: reprint p. 15 (19). 1934 ≡ Pycnophyllopsis cryptantha (Mattf.) Molinari in Polish Bot. J. 61: 276. 2016. – Holotype: Peru, Morococha, A. Raimondi 8392 (B†). – Neotype (designated by Timaná 2017: 6): Peru, Lima, Huarochirí, Paso de Anticona, Ticlio, 4850 m, 16 Dec 1998, Timaná & Tate 3767 (USM; isoneotype: MO-1100075!).

Morphological description — See Timaná (2005).

Distribution — The species is found in highland passes in Andean mountainous ranges between the departments of Puno and Lima in Peru at altitudes of 4800–5200 m.

Notes — According to Timaná (2017), this distinctive species, has tetramerous flowers and 2 free styles. The species, originally described by Mattfeld (1934) as Plettkea cryptantha, is characterized by decussate sepals with the inner pair shorter and non-ciliate as opposed to the outer pair. Molinari-Novoa (2016) described the new combination Pycnophyllopsis cryptantha (Mattf.) Molinari, without studying any type specimen; the holotype was destroyed and no neotype had yet been selected. Timaná (2017) solved this by selecting a new type for the species based on a specimen collected near the type locality by Raimondi in Lima. Later, Sharples & Tripp (2019) stated that Greenberg & Donoghue (2011) recovered a sample of Pycnophyllopsis cryptantha (Mattf.) Timaná from Peru as embedded within core Stellaria. The trnL-F sequence available in GenBank is resolved as sister to CAR431 ( Supplementary appendix S6 (wi.53.53301_Supplementary_appendix_S06_plastid_tree_with_sequences_from_GenBank.pdf)) that is the representative of S. cryptantha in our analysis.

6. Stellaria engleriana (Muschl.) Montesinos & Borsch, comb. nov. ≡ Arenaria engleriana Muschl. in Bot. Jahrb. Syst. 45: 449. 1911. – Lectotype (designated here): Peru, Junín, Tarma, La Oroya, encima de Tarma en el camino a La Oroya, 4000 m, A. Weberbauer 2542 (MOL [MOL00000453!]).

Morphological description — Perennial herb, diffuse caespitose, cushions 5–12 cm in diam.; root woody. Stems subwoody, lower parts clothed with a greyish-green thick bark, or very minutely ridged-reticulated, prostrate, sometimes rooting at nodes, 3–6 cm long, internodes 0.1–0.5 mm long, glabrous or with sparse slightly yellowish-whitish pubescence, trichomes 1–2 mm long. Leaves opposite, sessile; lamina lanceolate or ovate or rarely linear-lanceolate, fleshy or rarely membranous, thick, apex acute or mucronate, 5–10 mm long and 2–5 mm wide, hirsute near base and midvein, margin slightly hairy, midrib prominent on underside. Plants bisexual-hermaphrodite. Flowers subsessile or on short up to 0.5 mm long, glabrous peduncles, terminal and axillary; perigynous, cylindrical-oblong, 3.5–4.5 mm long and 1–1.8 mm wide; calyx cylindrical-turbinate; sepals 5, imbricate, ovate-oblong, slightly involute, yellow, 3–4 mm long and 1–1.5 mm wide, glabrous on surface but margins densely ciliate, apex acute-attenuate, folded and forming a narrow cylinder that covers capsule; petals 5, strongly reduced, yellowish to translucent, ovate, apex obtuse, 0.8–1.2 mm long and 0.3–0.5 mm wide; stamens 4 or 5, episepalous, 1.8–2.1 mm long; ovary ovoid-turbinate, 0.4–0.7 mm long and 0.4–0.6 mm wide, style 3-fid, stigma aciculate. Capsule subglobose, dehiscent with six valves, ovate-oblong, 1.3–1.7 mm long and 1.2–1.5 mm wide, containing 2–4 seeds, these lenticular, 0.7–1 mm in diam.; testa dark brown, bearing brown tubercles.

Distribution — Central Peru, in Junín and Huánuco departments, at altitudes of 4000–4400 m.

7. Stellaria galianoi Montesinos & Borsch, sp. nov. –Fig. 1C, 5C, D, 7;  Supplementary appendix S12 (wi.53.53301_Supplementary_appendix_S12_Stellaria_galianoi_isotype.jpg). Holotype: Peru, Cusco, Urubamba, Urubamba, Puerto Yanamayo, Patacancha, road to Ocobamba, 4440 m, 3 Apr 2016, D. Montesinos 4572 (HSP [HSP-9443!]; isotypes: B [B 10 0766217!], O [O-227237!], USM!).

Diagnosis — This species is easily distinguished by its long internodes (2–15 mm long), leaf laminas bearing white protuberances, absent characters in other species of Stellaria sect. Plettkea.

Morphological description — Perennial herb, forming diffuse mats, 4–8 cm high and 20–60 cm in diam.; roots fibrous. Stems decumbent or creeping 8–25 cm long, densely ramified at base and along whole length, glabrous, or nearly so (scarcely covered with minute papillae), covered by older leaves in central and lower parts; internodes 2–15 mm long. Leaves opposite, sessile; lamina oblanceolate-oblong to gladiate, plain or curved, nearly involute, glabrous on both sides, 3–5 mm long and 1.4–1.8 mm wide, midrib protuberant on underside, margin from base to mid of lamina with 4–7 multicellular pilose hairs (0.3–1 mm long, 6–14 cells) born on protuberances, usually persistent on older leaves; base truncated and apex aristulate; leaves pale green to yellow-brownish with age. Plants bisexual-hermaphrodite. Flowers perigynous, on rigid 7–15 mm long and glabrous peduncles, terminal, 2.2–3 mm long and 3–5 mm wide; calyx campanulate, glabrous; sepals 5, lanceolate, slightly involute, cupuliform at base, apex apiculate-aristulate, glabrous, 1.8–2.4 mm long and 0.8–1 mm wide, pale green to yellowish; petals 5, white, subglandular, ovate, with revolute obtuse apex, 2–3 mm long and 1–1.5 mm wide; stamens usually 10, episepalous, filaments often curved toward centre of flower, 0.3–0.5 mm long; anthers roundish to elliptical, reniform, yellowish and 0.15–0.3 mm long; style 3-fid, curved, glandular, pistil 0.5–0.7 mm long; stigma papillate or glandular; ovary cylindrical-ovoid, 0.7–1.1 mm long and 0.8–1.1 mm wide. Capsule ovoid, glabrous, c. 1.8 mm long and 2.5 mm wide, containing 10–12 seeds, these ovate or roundish, 0.6–0.8 mm long and 0.4–0.6 mm wide; testa brown, grooved, cells with bulgy stellate protuberances.

Distribution and ecology — Peru, Cusco, Urubamba. The species inhabits continuously moist environments dominated by tussock grasslands and bryophyte communities located on high passes that divide the inter Andean valleys, between the highland tropical forests and the puna scrublands in the upper basins near the Urubamba River lower slopes. The altitudinal range is 4230–4400 m and is restricted to this region. The exhaustive field collection of Caryophyllaceae in most parts of Peru for the past seven years and examination of nearly all available herbarium material did not reveal additional areas where the plant occurs. Nevertheless, further fieldwork in Urubamba is needed better understand the frequency and population structure of the species. Flowering specimens have been collected from March to May; fruiting specimens have been observed between April and June (pers. obs.). Associated taxa are: Gentianella sp. (Gentianaceae), Plantago rigida Kunth (Plantaginaceae), Senecio rhizomatus Rusby (Asteraceae) and Stellaria weddellii Pedersen (Caryophyllaceae), among others.

Etymology — The specific epithet refers to Prof. Washington Galiano (1950–), for his devoted career on studying the floristic diversity of the Cusco department in S Peru.

Notes — Stellaria galianoi is most likely monophyletic and is phylogenetically rather isolated among other members of the Plettkea clade (Fig. 3, 4). This species has the longest internodes of vegetative stems across the Plettkea clade, eventually, in the uppermost the internode is long, sometimes as reaching 1.5 cm. This character makes it easy to recognize among the apetalous taxa of Andean Stellaria. The new species differs from the known South American species of Arenaria by its leaf form and by the densely tuberculate seeds. Furthermore, S. galianoi differs from S. apurimacensis by the internode length (2–15 mm vs. 4–10 mm in S. apurimacensis), larger leaves (3–5 mm long and 1.4–1.8 mm wide vs. 2–3 mm long and 0.8–1.2 mm wide in S. apurimacensis), longer peduncles (7–15 mm vs. 2–5 mm in S. apurimacensis), narrower sepals (0.8–1 mm vs. 1–1.5 mm in S. apurimacensis) and larger seeds (0.6–0.8 mm long vs. 0.4–0.5 mm long in S. apurimacensis). Stellaria galianoi differs from S. andina in the leaf form (oblanceolate-oblong to gladiate vs. ovate in S. andina) and longer peduncles (7–15 mm vs. 1–4 mm in S. andina).

Fig. 7.

Morphological details of Stellaria galianoi – A: ramified stem; B: detail of pilosity on leaf surface; C: detail of leaves; D: mature flower with capsule; E: tuberculate seeds. – From Montesinos 4572. – Scale bars: A = 5 mm; B–E = 1 mm.

8. Stellaria keraiopetala (Mattf.) Montesinos & Borsch, comb. nov. ≡ Pycnophyllopsis keraiopetala Mattf. in Schriften Vereins Naturk. Unterweser, n.s., 7: reprint p. 22 (26). 1934. – Holotype: Bolivia, zwischen Palca und La Paz, an Felsen, 4800 m, Apr 1908, K. Pflanz 233 (B†). – Neotype (designated by Timaná 2017: 6): Bolivia, La Paz, Murillo, Cordillera Real, road to nevado Chacaltaya, N of Milluni crossing E of Lake Milluni along roadsides, 4600–4900 m, 25 Jan 2000, Timaná 3804 (LPB0000524; isoneotypes: BM, K, LL, MCSN, MICH, USM).

Morphological description — See Timaná (2005).

Distribution — The species is endemic to Bolivia and based on two collections and according to Timaná (2017), it is known to occur at altitudes of 4600–5100 m.

Notes — The neotype located at the Herbario Nacional de Bolivia, Universidad Mayor de San Andrés (LPB) was designated by Timaná since the original material collected by K. Pflanz 223 was lost (B†). According to Timaná (2017), Pycnophyllopsis keraiopetala (now Stellaria keraiopetala) is the only species with trimerous petals and stamens, although tetramerous and pentamerous forms are also found (sometimes all three forms in the same plant). Stellaria keraiopetala is the sister to S. weberbaueri, and both share the habit of dense small cushions with stems covered by overlapping leaves. Stellaria keraiopetala and S. weberbaueri appear to be geographically vicariant species due to its distribution in the highest parts of the Andes in Bolivia and Peru, respectively.

9. Stellaria laevis (Bartl.) Rohrb. in Linnaea 37: 275. 1872 ≡ Cherleria laevis Bartl. in Presl, Reliq. Haenk. 2: 12. 1831 ≡ Pycnophyllopsis laevis (Bartl.) Timaná in Lundellia 20: 8. 2017. – Lectotype (designated by Timaná 2017: 8): Peru, Quebrada de l'Obrachillo, s.d., Haenke s.n. (PR not seen; isolectotypes: GOET 000715!, HAL 0117903 image!).

= Cherleria bisulca Bartl. in Presl, Reliq. Haenk. 2: 12. 1831, syn. nov. ≡ Arenaria bisulca (Bartl.) Fenzl ex Rohrb in Linnaea 37: 248. 1872. – Type: Peru, Peru, 1791, T. P. X. Haenke s.n. (HAL01178886 [image!]).

Morphological description — See Timaná (2005).

Distribution — The species inhabits highland plateaus of the central Andes in Peru, at altitudes of 4660–4800 m, in the Lima and Junín departments. The environments where the species grows are highland plateau Andean grasslands with rocks, with template and harsh wind conditions.

Notes — Mattfeld (1934) tentatively included the species described by Bartling (1831) under the genus Cherleria into Plettkea. Mattfeld considered the characters mentioned in the original description as he had no access to specimens. Rohrbach (1872) transferred the species to Stellaria without further reference. Timaná (2017) encountered the Haenke specimen at PR and respective duplicates at HAL and GOET and argued that the species belongs to Pycnophyllopsis. The examination of the type specimen at GOET showed the presence of hirsute leaf margins, apetalous flowers supporting the position in the Plettkea clade. In the ITS tree specimen CAR912 of S. laevis is resolved as sister to S. cryptantha, albeit with low support (it was not possible to amplify plastid regions in this specimen). The examination of the type specimen further revealed the similarity with Arenaria bisulca (Bartl.) Fenzl & Rohrb. A species also described by Bartling (1831) under Cherleria, which is therefore put into synonymy in this study. Also, Zanotti & al. (2022) discussed if S. laevis could be closely related to Arenaria bisulca, an opinion to which we agree with due to the exact match of morphological characters. Moreover, S. laevis appears to be morphologically similar to S. andina having several differences such as the habit and growth form (loose mat-forming herb vs. weak herbs S. andina), leaf form and stiffness (rigid in S. laevis vs. weak in S. andina) and minor flower characteristics. Sequence data of ITS resolve S. laevis as part of subclade A within the Plettkea clade of Stellaria ( Supplementary appendix S9 (wi.53.53301_Supplementary_appendix_S09_ITS_tree_with_sequences_from_GenBank.pdf)).

10. Stellaria macbridei Montesinos & Borsch, nom. nov. ≡ Arenaria crassipes Baehni & J. F. Macbr. in Publ. Field Mus. Nat. Hist., Bot. Ser. 13(2): 598. 1937 [non Stellaria crassipes Hultén in Bot. Not. 1943: 261. 1943].

– Holotype: Peru, Lima, Río Blanco, 3000 m, prostrate on upland slopes, Macbride 812 (F [F0042702F image!]; isotypes: NY [NY00342439 image!], US [US00103284 image!]). – Fig. 1D.

Morphological description — Perennial herb, individual stems visible (not caespitose); root thick, reaching c. 4 cm deep. Stems 7–12 per individual, decumbent to ascending, 3–5 cm long; internodes 3–4 mm long, densely hirsute near nodes; trichomes irregularly shaped, multicellular, uniseriate, 0.5–1 mm long. Leaves, with broad and hirsute petioles, alternate; lamina oblong, 5–7 mm long and 2–2.5 mm wide, subcoriaceous or membranous, thickened at base, shiny, glabrous on both sides, thin, margins ciliate or hairy-ciliate, apex acuminate and slightly involute, only midrib hirsute. Plants bisexual-hermaphrodite. Flowers perigynous, on 1–1.8 mm long ciliate peduncles, axial and terminal; cylindrical-oblong, 2.5–3 mm long and 1.2–1.8 mm wide; calyx cylindrical-turbinate, thicker at base, crateriform; sepals 5, imbricate, narrowly lanceolate, 2–2.3 mm long and 0.4–0.6 mm wide, glabrous on surface, light green to bright yellow, apex acute-attenuate, involute, folded and forming a narrow cylinder that covers capsule; petals 5, reduced, translucent-stramineous, ovate, apex obtuse, 1–1.3 mm long and 0.2–0.4 mm wide; stamens 4 or 5, episepalous, 1–1.5 mm long; ovary ovoid-turbinate, 0.4–0.8 mm long and 0.6–0.8 mm wide, style 3-fid, stigma aciculate. Capsule ovoid, 0.9–1.2 mm long containing 4 seeds, these orbicular, 0.2–0.3 mm in diam., testa reddish-maroon and shiny, cells bearing light maroon tubercles.

Distribution and ecology — Stellaria macbridei is endemic to central Peru (Cano & Sánchez Vega 2006) occurring in puna grasslands ecosystems that receive continuous rainfall throughout the year, it is distributed in Áncash, Huánuco, Junín and Lima departments at altitudes of 4200–4800 m.

Etymology — The specific epithet refers to J. F. Macbride (1892–1976), American botanist who provided the last comprehensive revision for Stellaria and Arenaria from Peru and also was one of the authors who originally described this species.

Notes — Macbride (1936) mentioned that Stellaria macbridei has similarities with S. congesta but differs from that species by the tuber-like root and the small erect habit. Other differences include suboblong leaf form (ovate in S. congesta) and the narrowly lanceolate sepals (lanceolate in S. congesta). The two sequenced specimens are sisters and form a distinct lineage within the Plettkea clade in both the plastid and nuclear trees (Fig. 3, 4) underscoring the identity of S. macbridei as a distinct and eventually monophyletic species.

11. Stellaria macrophylla (Muschl.) Montesinos & Borsch, comb. nov. ≡ Pycnophyllum macrophyllum Muschl. in Bot. Jahrb. Syst. 45: 458. 1911 ≡ Plettkea macrophylla (Muschl.) Mattf. in Schriften Vereins Naturk. Unterweser, n.s., 7: reprint p. 18 (22). 1934 ≡ Pycnophyllopsis macrophylla (Muschl.) Molinari in Polish Bot. J. 61: 276. 2016. – Lectotype (designated by Molinari-Novoa 2016: 276): Peru, Áncash, Cordillera Blanca, 4500 m, 14 May 1903, A. Weberbauer 2975 (MOL00000509!).

Morphological description — See Timaná (2005).

Distribution — Huascarán National Park in Áncash department, central Peru, at altitudes of 4500–4800 m (Timaná 2017).

Notes — Muschler (1911: 458) described Pycnophyllum macrophyllum based on the leaf shape and few relevant flowers characters. Molinari-Novoa (2016) simply transferred the species to Pycnophyllopsis referring to Timaná (2005) who recognized Pycnophyllopsis s.l. (including Plettkea) as distinct from Pycnophyllum without any own analysis of plant material. According to Timaná (2017), Stellaria macrophylla differs from S. cryptantha in the number of floral parts: S. macrophylla is pentamerous with three free styles while S. cryptantha a tetramerous species with two free styles. In addition, the leaves of S. macrophylla are slightly narrower toward the apex, where in S. cryptantha these are more triangular. The only collection known is the type specimen at MOL. This specimen has no seeds which was also confirmed by physical examination (G. Tello, Lima, pers. comm.). Therefore, it is unclear from where Muschler took the information on seeds, which does not even correspond to specimens of the Plettkea clade and therefore could be wrong.

12. Stellaria patagonica Montesinos & Borsch, nom. nov. ≡ Pycnophyllopsis muscosa Skottsb. in Kongl. Svenska Vetensk. Acad. Handl., n.s., 56(5): 216. 1916 [non Stellaria muscosa (L.) Jess., Deut. Excurs.-Fl.: 288. 1879 ≡ Moehringia muscosa L., Sp. Pl. 1: 359. 1753]. – Lectotype (designated by Timaná 2017: 6): Argentina, Patagonia Andina, territorio Chubut, Meseta Chala, c. 1300 m, 5 Dec 1908, Skottsberg 606 (S [S05-10321 image!]; isolectotypes: LD [LD1418578 image!], SG [SGO000001982 image!]).

Morphological description — See Timaná (2005).

Distribution — Patagonian plateaus in Argentina, at altitudes of 800–1300 m, in open slopes, rocky and very windy.

Etymology — In allusion to the Patagonia region in Argentina where the species grows.

Notes — The species shows morphological affinities to Stellaria sect. Plettkea, such as short stems bearing short internodes, densely appressed leaves with ciliate margins, apical, solitary flowers, shortly pedunculate, bearing five sepals and an equal number of reduced petals, so to be placed under Stellaria. The type specimen has no seeds and the protologue does not mention any seed characters.

13. Stellaria pedunculosa (Wedd.) Montesinos & Borsch, comb. nov. ≡ Arenaria pedunculosa Wedd. in Ann. Sci. Nat., Bot., ser. 5, 1: 294. 1864. – Lectotype (designated here): Bolivia, La Paz, Ravin de Chuquiaguillo, 1851, H. Weddell s.n (P [P 00274242 image!]). – Fig. 1E.

Morphological description — Annual herb, forming small caespitose tufts, 1–2 cm high and 2–3.5 cm in diam.; roots fibrous. Stems few, often further ramified at base; internodes 1–4.5 mm long, glabrous. Leaves opposite, sessile; lamina oblong-ovate, 4–6 mm long and 1–1.6 mm wide, thin, to some extent curved at tip, rarely involute, scarcely covered by tomentulose hairs on upper- and underside, midrib inconspicuous; base truncated and apex acute, margin tomentulose with multicellular hairs 0.1–0.25 mm long (occasionally mammillate and without distinct trichomes), usually persistent on older foliage; leaves pale green to yellow-brownish with age. Plants bisexual-hermaphrodite. Flowers perigynous, on rigid 8–11 mm long peduncles covered with minute papillae, terminal, ovoid, 2–2.6 mm long and 1–1.6 mm wide; calyx cylindrical-campanulate, crateriform; sepals 5, ovate, 1.8–2.4 mm long and 0.8–1 mm wide, slightly involute, green to yellowish-translucent with age, cupuliform at base, apex acute, mucronate, pale green to yellowish, surface glabrous, margins with scattered papillae, 0.08–0.1 mm long; petals 5, reduced, light green, ovate, obtuse, equalling sepals or shorter, 1.2–1.5 mm long and 0.6–0.8 mm wide; stamens 5, very short, 0.2–0.4 mm long, episepalous; style 3-fid, glandular, 0.25–0.35 mm long, aciculate; ovary ovoid, 0.2–0.5 mm long and 0.3–0.5 mm wide. Capsule ovoid, c. 1 mm long, glabrous, containing 2–5 seeds, these orbicular, 0.6–0.8 mm in diam., testa brown-yellowish, granulate.

Distribution — Based on two collections (DBMT 5395b, 4565), Arenaria pedunculosa is located at the lower slopes SE of Ticsani volcano (Moquegua department), on volcanic pumice soils at altitudes of 4500–4820 m. Flowers and fruits were observed between February and March. In Bolivia the species is known only from the type collection, and a search of material at LPB in 2019 provided no evidence that the species has been collected again.

Vernacular name — Jiska Volcanqura Panqara, given in Aymara language (Kent Chicalla, Moquegua, pers. comm.).

Notes — Even though the intense survey done at the herbaria mentioned in the methods, no specimens have been found as additional collections for Bolivia, but two specimens have been found from the Moquegua department in Peru.

14. Stellaria smithii (Timaná) Montesinos & Borsch, comb. nov. ≡ Pycnophyllopsis smithii Timaná in Lundellia 20: 10. 2017. – Holotype: Peru, Lima, Huarochirí, Paso de Anticona, Ticlio, 4850 m, 16 Dec 1998, Timaná & Tate 3768 (USM!; isotypes: BM, F, K!, LL, LPB [LPB0000525], MICH).

Morphological description — See Timaná (2005).

Distribution — According to Timaná (2017), the species should be distributed in the boundary between the Peruvian departments of Lima and Junín, at altitudes of 4300–4900 m, but should also be present in the Áncash department (Huascaran National Park) at an altitude of c. 4800 m. However, no further specimens in addition to the type appear to be known.

Notes — The characters such as the imbricate, lanceolate, stiff leaves, with ciliate margin, the short flower peduncles and the staminoid petals are considered to provide evidence for the inclusion of the species in the Plettkea clade.

15. Stellaria spinulosa Montesinos & Borsch, nom. nov. ≡ Arenaria aphanantha Wedd. in Ann. Sci. Nat., Bot., ser. 5, 1: 293. 1864 [non Stellaria aphanantha Griseb. in Abh. Königl. Ges. Wiss. Göttingen 24: 27. 1879]. – Lectotype (designated here): Peru, 1839–1840, C. Gay 1818 ([P(P00335797)]; isolectotype: ([MO-840929]).

Morphological description — Perennial herb, varying from few stems up to 50 cm long to forming dense mats 2–4 cm high; root woody. Stems decumbent, creeping and with branches distinctly shorter than stems, bearing remains of old foliage along stems; internodes 1–1.5 mm long; sparsely pubescent with erect 0.1–0.3 mm long trichomes. Leaves alternate, lamina lanceolate to linear-lanceolate, 4–6 mm long and 1–1.5 mm wide, coriaceous, with acuminate to subaristate apex, densely ciliate near truncate base. Plants bisexual-hermaphrodite. Flowers perigynous, terminal, on hirsute, thick, 3.5–4 mm long peduncles, but these hidden by uppermost leaves; calyx cylindrical to rarely subcampanulate, 3.5–4 mm long and 1.5–2 mm wide, crateriform, usually thickened at bottom; sepals 5, lanceolate, cupuliform at base, involute, 3–3.5 mm long and c. 0.8 mm wide, apex acute, light green to pale yellowish, glabrous on surface and along margins; petals 5, strongly reduced, translucent, ovate, apex obtuse, 1.2–1.6 mm long and 0.7–0.8 mm wide; stamens 4 or 5, episepalous, 1.1–1.3 mm long; ovary cylindrical-turbinate, 0.5–0.7 mm long and 0.6–0.8 mm wide, style 3-fid, stigma aciculate. Capsule ovoid, c. 1 mm long, containing 2 or 3 seeds, orbicular, 0.5–0.6 mm in diam., testa maroon, shiny and distinctly tuberculate, cells bearing whitish asymmetrical protuberances.

Distribution — Stellaria spinulosa occurs in a variety of highland ecosystems across Peru and is considered as the most collected species of the clade (as observed in the material from the different herbaria visited) and extends to Ecuador. Jørgensen & León-Yánez (1999) mentioned the occurrence of the species in Ecuador, which can be confirmed based on an analysis of material stored at MO according to Tropicos.org (2023) and as evaluated by the first author during two visits to MO in 2013 and 2016 and more recently, at PRC, four collections were identified to be S. spinulosa located mostly in central Ecuador, between Chimborazo and Cuicocha. The altitudinal range is from 2800–5000 m according to the specimens evaluated.

Etymology — The epithet refers to the spine-like leaves of the plant, which can be felt as tingling by simple touch; spinulosa is derived from the Latin spinula (small spine) in relation to the thorny and pungent characters of the leaves. The former epithet aphanantha is derived from the Greek aphanes (invisible obscure) and anthos (flower), probably referring to the resemblance of the flower sepals to the leaves.

Notes — The specimen C. Gay 1818 (P00335797) is selected as the lectotype for being most representative with a complete set of morphological characters. As evidenced by this specimen, the species is easily distinguishable from the other members of the clade by the intense yellowish colour of the stems and leaves, the stiff ovate leaf lamina and the nearly sessile flowers with long calyx, the presence of staminoid petals reduced to filaments and the tubercle seeds, which is characteristic for this kind of habit.

16. Stellaria standleyi (Baehni & J. F. Macbr.) Montesinos & Borsch, comb. nov. ≡ Arenaria standleyi Baehni & J. F. Macbr. in Publ. Field Mus. Nat. Hist., Bot. Ser. 13(2): 604. 1937. – Lectotype (designated here): Peru, Ayacucho department, Mt. Razuhuillca, Prov. Huanta, 4200 m, A. Weberbauer 7489 (F-562398!).

Morphological description — Perennial herb, caespitose, densely branched, cushions 1–4 cm high and 10–15 cm in diam.; roots subwoody. Stems numerous, densely covered by stiff foliage; internodes 0.1–0.3 mm long, glabrous; leaves alternate, lamina ovate to linear-lanceolate, 3–4 mm long and 1–1.5 mm wide, thick and glossy, apex acute and base truncate, yellowish in colour and glabrous on both sides, midrib prominent on underside, margins usually folded toward underside, densely covered by a narrow band of trichomes < 0.1 mm long. Plants bisexual-hermaphrodite. Flowers perigynous, terminal and axillary, on 1–2 mm long glabrous peduncles, oblong, 3–3.5 mm long and 0.8–1.1 mm wide; calyx cylindrical-turbinate, crateriform, thicker at base, 2.7–3.2 mm long and 2.5–3.4 mm wide; sepals 5, imbricate, ovate, 2.5–3 mm long and 0.5–1 mm wide, glabrous on surface, green or pale green to yellowish-translucent with age, involute, apex acuminate; petals 5, reduced, white-translucent, ovate, apex obtuse, 2–2.4 mm long and 0.3–0.4 mm wide; stamens 4, episepalous, anthers orbicular-ovate, yellowish-translucent, 0.3–0.4 mm long; ovary ovoid-turbinate, 0.6–0.9 mm long and 0.6–0.8 mm wide, style 3-fid, stigma aciculate, pale white. Capsule ovoid, 1.2–1.5 mm long and 1.1–1.3 mm wide, glabrous, containing 3–5 seeds, these ovoid, c. 0.5 mm long, testa brown, tuberculate.

Distribution — Peru, Ayacucho department at an altitude of c. 4200 m in open grasslands in Puna ecosystems characteristic of the central Andes. No further collections were found, so this is to be considered as a rare species.

Notes — The collection A. Weberbauer 7489 shows the typical characters of Stellaria sect. Plettkea by sharing the leaf size, texture, and form, as well as the flower and seeds characteristics as described in the morphological description. Because Macbride (1937) did not mention a specific type specimen in the protologue, a lectotypification is made here, using the locality information in the protologue that matches with the Weberbauer specimen that also exhibits the morphological characters described.

17. Stellaria tetrasticha (Mattf.) M. T. Sharples & E. A. Tripp. in Syst. Bot. 44: 871. 2019 ≡ Plettkea tetrasticha Mattf. in Schriften Vereins Naturk. Unterweser, n.s., 7: reprint p. 21 (25). 1934 ≡ Pycnophyllum mattfeldii J. F. Macbr. in Publ. Field Mus. Nat. Hist., Bot. Ser. 13(2): 611. 1937 [non Pycnophyllum tetrastichum J. Rémy in Ann. Sci. Nat., Bot., ser. 3, 6: 356. 1846] ≡ Pycnophyllopsis tetrasticha (Mattf.) Timaná in Lundellia 20: 8. 2017. – Holotype: Peru, Áncash, Cajatambo, Schwarze Cordillere über Ocros, auf dürftig bewachsenem, steinigem Boden, 4500–4800 m, A. Weberbauer 2804a (B†). – Neotype (designated by Timaná 2017: 8): Peru, Áncash, Yungay Province, Huascarán National Park, Llanganuco sector, Quebrada Demanda, W of Chacraraju base camp, 09°01′S, 77°36′W, 4750–4900 m, 13 Apr 1985, D. N. Smith & V. Cautivo 10287 (MO-052068!; isoneotype: F!).

Morphological description — See Timaná (2005).

Distribution — Central Peru, Áncash department inside the Huascarán National Park on highland peaks at altitudes of 4500–4900 m, where considered a narrow endemism.

Notes — Stellaria tetrasticha was originally described as a member of the genus Plettkea by Mattfeld (1934) and later accepted by Bittrich (1993). The species has a mat form with spreading stems, ovate leaves c. 2 mm long bearing carinate acute apex and sepals with ovate-oblong form. Later, Timaná (2017) named Pycnophyllopsis tetrasticha (Mattf.) Timaná based on the morphological affinities found within flower measurements in the neotype he selected. Sharples & Tripp (2019) included a sample of the species in their phylogenetic analysis showing it to be strongly supported as a member of the Plettkea clade.

18. Stellaria utcubambensis Montesinos & Borsch, sp. nov. – Fig. 1F, 5E, F, 8;  Supplementary appendix S13 (wi.53.53301_Supplementary_appendix_S13_Stellaria_utcubambensis_isotype.jpg). Holotype: Peru, Amazonas, Chachapoyas, Leymebamba, Tajopampa Camino Inca, 3696 m, 14 Aug 2016, D. Montesinos 4979 (HUT [HUT-60181!]; isotypes: B [B 10 0766222!], O [O-227246!], USM!).

Diagnosis — The species can be easily distinguished from the other members of the clade by the stiff linear-lanceolate leaves and the prominent calyx apex that forms a needle-like stiff point, a feature that is not seen in any other species.

Morphological description — Perennial herb, forming mats 2–4 cm high and 10–30 cm in diam.; roots fibrous. Stems suberect or decumbent to prostrate, trailing, densely ramified at base, clothed with older leaves down to base; internodes 2–4 mm long, nodes slightly thickened, glabrous, yellowish. Leaves opposite, narrowly involute or plane, eventually curved with age, lamina linear-lanceolate, stiff and coriaceous, truncate at base and aristulate-acuminate near apex, 4–6 mm long and < 1 mm wide, glabrous on both sides, midrib prominent on underside, margins glabrous toward apex, basally with 0.1–0.3 mm long trichomes. Plants bisexual-hermaphrodite. Flowers perigynous, terminal and axillary, always suspended on 2–5 mm long, erect and glabrous peduncles; calyx cylindrical, 4–6 mm long and 0.8–1.1 mm wide; sepals 5, ovate-lanceolate, 4–6 mm long and c. 1 mm wide, involute, glabrous on both sides except at base of margins, where minute c. 0.1 mm long trichomes are present, truncate at base and cuspidate at apex, midrib excurrent as a thin 0.1–0.25 mm long needle, surface greenish-white turning yellowish with age; petals 5, deeply bifid, bright white, ovate-elliptical, in total 7–10 mm long, lobules ovate-lanceolate 0.3–0.6 mm long and 0.3–0.5 mm wide; filaments c. 0.4 mm long, stamens 5–10, episepalous, c. 0.4 mm long, anthers 0.1–0.2 mm long, styles 3-fid, ovary ovoid, 0.2–0.3 mm long and c. 0.3 mm wide. Capsule ovoid or nearly so, 0.6–0.8 mm long and c. 0.5 mm wide, containing 3 seeds, these roundish or nearly so, flattened, 0.4–0.5 mm in diam., testa dark maroon to blackish, covered with rectangular stellate tubercules.

Fig. 8.

Morphological details of Stellaria utcubambensis – A: ramified stems with flower; B: leaves; C: mature flowers; D: flower capsule; E: tuberculate seeds. – Montesinos 4572. – Scale bars: A–C = 1 mm; D = 0.5 mm; E = 200 µm.

Distribution and ecology — The species inhabits the mountain summits of the tributaries leading to the Utcubamba river in the Amazonas department in N Peru, with an expected growth at altitudes of 3600–3900 m. The species was found in areas where slope burning is an unfortunate practice applied by the local people; such events and climate change could lead to the gradual disappearance of this species. Flowering has been observed during the months of September and November.

Etymology — The specific epithet refers to the Utcubamba river in N Peru that divides Amazonas department from south to north. The new species was found in its uppermost tributaries, and it is very likely that there are further populations on the mountains draining into this river.

Notes — This species is known so far from only one collection, but further populations might be encountered after searching in the field. Stellaria utcubambensis differs from S. apurimacensis by having leaves stiff, linear-lanceolate and with margins glabrous toward apex (vs. weak, elliptical-lanceolate and with margins sparsely pilose in S. apurimacensis). Moreover, the internodes in S. utcubambensis are 2–4 mm long (vs. 4–10 mm long in S. apurimacensis) and the calyx is cylindrical (vs. campanulate in S. apurimacensis).

19. Stellaria villasenorii Montesinos & Borsch, nom. nov. ≡ Pycnophyllum lanatum Phil. in Anales Univ. Chile, I, Mem. Ci. Lit. 81(6a): 774. 1892 [non Stellaria lanata Hook. f., Fl. Brit. India 1: 232. 1874] ≡ Baretia lanata (Phil.) Timaná in Adansonia, ser. 3, 45: 502. 2023. – Lectotype (designated by Timaná 2023: 502): Chile, Las Mollacas, Cordillera de Illapel, Jan 1888, R. Philippi s.n. (SGO000001980 [image!]).

Morphological description — See Timaná (2005).

Distribution — Mountain plateaus in Coquimbo, Chile, at altitudes of 2600–2800 m, endemic.

Etymology — The species name is chosen to honour Rodrigo A. Villaseñor Castro (1947–, Concepción, Chile), a professor in Biology and Natural Sciences, who extensively contributed to the knowledge of the Chilean flora.

Notes — The species conspicuously deviates from the other members of the Plettkea clade by its dense lanuginose indumentum and by its shrubby habit.

Timaná (2005) proposed to classify this species in its own new subgenus, Pycnophyllopsis subg. “Coquimbo”, but this name, because it appeared in a thesis, was not effectively (and therefore not validly) published according to Art. 30.9 of the Code (Turland & al. 2018). The same applies to the species combination under Pycnophyllopsis and the lectotypification, all of which were not included in Timaná's (2017) paper on the genus. Flower and seed morphology provide evidence for a position in the Plettkea clade. In his thesis, Timaná (2005) depicted a representative of this species in an ITS tree in a lineage with Pycnophyllopsis cryptantha and P. weberbaueri, thus supporting this position. However, these phylogenetic results cannot be reproduced because the sequences are not available and the tree was never properly published.

There are two specimens at SGO (old herbarium number 048875 corresponding to barcode SGO000001980 and old herbarium number 090982 corresponding to barcode SGO000001981) that were apparently collected by Philippi from the same locality, but the latter lacks a date.

20. Stellaria weberbaueri (Muschl.) Montesinos & Borsch, comb. nov. ≡ Pycnophyllum weberbaueri Muschl. in Bot. Jahrb. Syst. 45: 455. 1911 = Plettkea weberbaueri (Muschl.) Mattf. in Schriften Vereins Naturk. Unterweser, n.s., 7: reprint p. 19 (23). 1934 ≡ Pycnophyllopsis weberbaueri (Muschl.) Timaná in Monogr. Syst. Bot. Missouri Bot. Gard. 127: 1271. 2014. – Lectoype (designated here): Peru, Vincocaya, statio viae ferreae ad Arequipam, 4100 m, 24 Aug 1902, A. Weberbauer 1373 (MOL [MOL 00000507!]). – Fig. 1G.

Morphological description — See Timaná (2005).

Distribution — The species inhabits highland plateaus, also known as subnival puna, at altitudes of 4660–5000 m. It is known to occur in the Arequipa and Moquegua departments of Peru, while its occurrence in the Bolivian Andes is not confirmed.

Notes — The species was first described as Pycnophyllum weberbaueri Muschl. by Muschler (1911), presumably based on the cushion growth form, plicate leaves and apical flowers. Later, the species was transferred to the genus Pycnophyllopsis by Timaná (2017), as Pycnophyllopsis weberbaueri (Muschl.) Timaná, based on the consistently pentamerous flowers with three free styles. Muschler (1911) apparently described characters for Stellaria weberbaueri such as true petals, which are actually not present in the specimens examined. Moreover, S. weberbaueri has leaves that do not overlap to be completely imbricate, giving the general impression of a loose cushion with longer internode length. Sharples & al. (2021) reported “Stellaria weberbaueri (Muschl.) M. T. Sharples & E. A. Tripp” in their Appendix 2, but this name has not been validly published anywhere.

21. Stellaria xanthophylla Montesinos & Borsch, sp. nov. – Fig. 1H, 5G, H, 9;  Supplementary appendix S14 (wi.53.53301_Supplementary_appendix_S14_Stellaria_xanthophylla_isotype.jpg). Holotype: Peru, Amazonas, Chachapoyas, Leymebamba, construcciones de piedra, restos arqueológicos La Boveda, 3540 m, 20 Jun 2018, D. Montesinos 6970a (HSP [HSP-20000!]; isotype: B [B 10 1098616!]).

Diagnosis — This species is similar to Stellaria laevis, from which it can easily be distinguished by its leaf margin, which is ciliate in the lower-middle part of the leaf, whereas in S. laevis the margin is completely covered by thin trichomes.

Morphological description — Perennial herb, forming dense mats, 6–10 cm high and up to 20 cm in diam.; root woody. Stems decumbent or more commonly curved, 10–18 cm long, branched; internodes 1–5 mm long, glabrous, sometimes bearing a few trichomes at node base, nodes thickened. Leaves involute, opposite, basally fused, lamina ovate-lanceolate to linear-lanceolate, subtruncate at base and mucronate at apex, stiff or spine-like, 6–8 mm long and 1–1.5 mm wide, glabrous, thick, with midrib prominent, densely covered by thin trichomes at base, tending to be glabrous toward apex; trichomes multicellular, straight or curved, 0.2–0.5 mm long, increasing in length toward base of lamina; older foliage usually covering stems, yellowish in colour. Plants bisexual-hermaphrodite. Flowers perigynous, terminal and axillary, on erect or slightly curved, 5–15 mm long peduncles, bearing tiny protuberances on surface as well as minute trichomes, rarely glabrous, old flowers persistent; calyx cylindrical, imbricate, turbinate, slightly wider at base, 8–10 mm long and 1.4–2.2 mm wide; sepals 5, lanceolate to narrowly ovate-lanceolate, involute, pale green to dark yellow with age, 5–7 mm long and 1.5–2 mm wide, midrib prominent, margins entire, truncate at base, acute at apex, surface glabrous or nearly so; petals 5, strongly reduced, 2–3 mm long and 1–1.8 mm wide, translucent, elliptical, apex obtuse; stamens 5, 1.5–2 mm long; style 3-fid, less than 1 mm high; ovary cylindrical, 0.9–1.1 mm long and 0.8–1 mm wide, stigma aciculate and obtuse. Capsule ovoid, 0.8–1 mm long, glabrous, containing 4–6 seeds, these ovate, compressed, c. 1 mm in diam., testa maroon, densely tuberculate.

Fig. 9.

Morphological details of Stellaria xanthophylla – A: flowering stem; B: stem with leaves; C: leaves; D: mature flowers. – From Montesinos 6970a. – Scale bars: A–D = 1 mm.

Distribution and ecology — The species is recorded in northern and central Peru, in the mountains adjacent to the Alto Marañón river in Huari province, Áncash department, and in the Utcubamba high mountains river basins in southern Amazonas department, near the boundary with La Libertad and San Martín departments. An additional specimen to the one sequenced comes from the department of Áncash in Peru: Huari, San Pedro de Chaná 4410 m, 5 May 2018, D. Montesinos & G. Sancho 6147 (B-101249409!, HCSM!, HSP-12974!, HUT-62033!, USM!). The habitat varies in vegetation cover and floristic composition but not in precipitation, as these environments tend to receive over 800 mm/year. The typical ecosystem is humid puna grasslands, with rocky outcrops and highland subhumid forest patches with species of Hesperomeles Lindl. (Rosaceae) and Verbesina L. (Asteraceae).

Etymology — The specific epithet derives from the Greek words xanthos, yellow, and phylla, leaves, referring to the persistent, yellow leaves along the stems of the plant.

Notes — Stellaria xanthophylla shows morphological similarities with S. engleriana but can be differentiated by the following characters: bearing thin trichomes at the base of the lamina (vs. dense trichomes at the base in S. engleriana); sepal form, size and texture (lanceolate to narrowly ovate-lanceolate, 5–7 mm long and 1.5–2 mm wide, surface and margins glabrous or nearly so in S xanthophylla vs. ovate-oblong, 3–4 mm long and 1–1.5 mm wide, with a ciliate lamina surface and margin in S. engleriana).