Species proposed on the basis of one or few individuals present a difficulty that transcends all modes of inference and all systematic data sources, including morphological and molecular data. This is particularly true for the liverwort family Lejeuneaceae, as these plants are inherently variable, differences between groups are frequently quantitative, and few specimens or limited material preclude destructive investigations, including molecular approaches. Here we use an extreme case of a single specimen to demonstrate how an integrated approach to character assessment and transparent decision processes can be used to provide sufficient evidence to support the hypothesis of species differences. To make progress on the single-specimen problem, an assessment of homology is essential to discriminate intra from interspecific variation in characters. Furthermore, an assessment of homology can substantiate differences between species of leafy liverworts in situations where the weight of character differences alone cannot because it is grounded in a phylogenetic framework. When homologous character systems and character states are equated with difference, the absence (or at least delayed development) of a stipe in Nephelolejeunea carcharias provides sufficient evidence for us to reject the hypothesis that this species is the same as N. talinayi because of what we know about the expression of perianth stipes in related species. As an inferential tool, homology exhibits considerable utility to liverwort taxonomists because it furnishes us with reasonable grounds on which to test hypotheses of relationship even in extremely observation-limited situations such as the one treated here.

The occurrence and diversity of Potamogeton hybrids was investigated in eastern North America, the region of the highest diversity of Potamogeton species in the world. For various reasons, however, the existence of hybrids in this area has been largely overlooked. ITS direct sequencing and RFLPs revealed four previously unknown hybrids, which are described as Potamogeton ×aemulans (P. bicupulatus × P. epihydrus), P. ×mirabilis (P. gramineus × P. oakesianus), P. ×versicolor (P. epihydrus × P. perfoliatus), and P. ×absconditus (P. perfoliatus × P. richardsonii). These are the first confirmed hybrids involving P. bicupulatus, P. epihydrus, P. oakesianus, and P. richardsonii. Another hybrid, P. ×nitens (P. gramineus × P. perfoliatus), is for the first time confirmed for North America with molecular markers. The hybrids' maternal parents were revealed by cpDNA sequencing. Phenotypically, two of the hybrids more closely resemble other taxa than their parents. Hybrid diversity and recognition in North America and in Europe are compared. Morphological versus molecular identification of hybrids, occurrence of hybrids in the absence of their parents, parental species relationships, long-term persistence of hybrid clones, vegetative dispersal, frequency of hybridization events, and hybrid distribution patterns are discussed.

Potamogeton is a taxonomically problematic genus of aquatic monocotyledons, which has received limited phylogenetic study using molecular data. The group is known for extensive vegetative plasticity, confusing patterns of morphological variation and propensity for hybridization. Potamogeton gemmiparus and P. vaseyi are of conservation concern in North America where both are listed as imperiled. These vegetatively similar species are particularly difficult to distinguish in the absence of floating leaves. We studied both species and putatively related taxa in subsection Pusilli (e.g. P. clystocarpus, P. foliosus, and P. pusillus) to elucidate relationships and to develop an identification method using molecular markers. Phylogenetic analyses of nrITS and trnK 5′ intron sequence data clearly endorse the recognition of P. gemmiparus and P. vaseyi as distinct species but call into question the subspecific circumscription of P. pusillus currently followed in North America. Our data resolved P. pusillus in a clade with P. foliosus, separated substantially from P. berchtoldii (= P. pusillus subsp. tenuissimus), thus supporting the recognition of P. berchtoldii as a distinct species. Using molecular cloning techniques, we documented three clear examples of interspecific hybridization (P. foliosus × P. pusillus, P. berchtoldii × P. vaseyi, and P. gemmiparus × P. vaseyi). Simple DNA polymorphisms also indicated several P. berchtoldii × P. gemmiparus hybrids. The narrowly distributed P. gemmiparus and P. clystocarpus are similar morphologically and genetically to the wide-ranging P. berchtoldii, with which they both hybridize. We recommend either the recognition of P. gemmiparus and P. clystocarpus as distinct species, or more suitably as subspecies of P. berchtoldii, for which two new combinations are provided: P. berchtoldii subsp. gemmiparus and P. berchtoldii subsp. clystocarpus.

Comparative morphological studies of specimens included in Dioscorea gillettii from Kenya and Ethiopia show differentiation between a northern group of populations in Sidamo and Bale Provinces in Ethiopia and near Moyale in northern Kenya and a southern group found in Kitui and Meru Districts of Kenya. Thus the southern element is described as a new species. The two species also differ in their pollen morphology. An illustration, distribution map, and a conservation status assessment are provided for D. kituiensis, and its mode of speciation is discussed.

The genus Quesnelia presently includes 18 species, which occur mainly near the east coast of Brazil from the states of Rio de Janeiro to Bahia. The genus has been divided into two subgenera, Quesnelia and Billbergiopsis. However, its generic and subgeneric delimitation is artificial: in several classifications proposed in the family, different investigators have questioned the naturalness of the group, noting its affinity with species of Aechmea and Billbergia. With the objective of assessing the monophyly of the genus, and evaluating the subgeneric delimitation and the relationship of its species to other genera, a phylogenetic analysis was carried out based on parsimony. The analysis included 33 taxa, with 92 morphological characters. The genera Quesnelia and Aechmea emerged as polyphyletic, and Billbergia as monophyletic. In regard to the subgeneric classification, Quesnelia subgenus Quesnelia emerged as monophyletic, and Quesnelia subgenus Billbergiopsis as polyphyletic. The majority of the species of Quesnelia subgenus Billbergiopsis emerged as the sister group to Billbergia. Even when anatomical and palynological characters were included, the consistency index of the tree obtained was low, indicating high levels of homoplasy. In addition, the majority of clades did not have good statistical support. Therefore, taxonomic changes are not proposed because these would be premature.

A phylogenetic analysis of five coding and noncoding chloroplast loci, totaling 6.6 kb of aligned nucleotide and indel characters, suggests that the large neotropical bamboo genus Chusquea is embedded within the much smaller Andean genus Neurolepis. Monophyly of each taxon was anticipated due to the unique occurrence of dimorphic multiple buds in Chusquea and the lack of aerial branching in Neurolepis. We tested whether the unexpected placement of Chusquea might be the result of a biased analysis. Both Neurolepis and the outgroup taxa have long branches that could influence rooting and inferred ingroup relationships. A number of methods were employed to test for long-branch attraction and sampling effects in our topology. Alternative hypothesis testing using a conservative form of the Shimodaira-Hasegawa test indicated that paraphyly of Neurolepis is a significantly better explanation of the data than monophyly, even when models of character evolution are changed. Given the robustness of the topology, high support measures for clades on the tree, and the results of the Shimodaira-Hasegawa tests, we conclude that chloroplast genomes indicate probable paraphyly of Neurolepis with respect to Chusquea. The species of Neurolepis are therefore transferred to Chusquea, resulting in the following new combinations and names: Chusquea acuminatissima, C. angusta, C. asymmetrica, C. cylindrica, C. diversiglumis, C. elata, C. fimbriligulata, C. laegaardii, C. magnifolia, C. mollis, C. nana, C. nobilis, C. petiolata, C. rigida, C. silverstonei, C. spectabilis, C. steyermarkii, C. stuebelii, C. tovari and C. villosa. The names Neurolepis elata, N. stuebelii, N. weberbaueri, Planotia ingens, and P. tessellata are lectotypified.

The present contribution continues a critical revision of Panicum, particularly with the delimitation of “incertae sedis” taxa. A phylogenetic analysis of Paniceae based on cpDNA sequence data (ndhF) was performed with special emphasis on section Stolonifera of Panicum. Fourteen sequences of species of sect. Stolonifera and Echinolaena were added to a panicoid grass matrix previously published giving a total of 140 sequences. As a result, Ocellochloa is here described as a new genus including 12 new combinations: O. andreana, O. biglandularis, O. brachystachya, O. chapadensis, O. craterifera, O. irregularis, O. latissima, O. piauiensis, O. pulchella, O. rudis, O. soderstromii, and O. stolonifera. The position of Panicum venezuelae, previously placed in section Stolonifera with the above mentioned species, clearly indicates that this species is not closely related to the Ocellochloa clade. This conclusion is supported by several morphological characters, such as the presence of axillary inflorescences, cleistogamous spikelets, and glands of the lower lemma depressed, not crateriform. Ocellochloa differs from Panicum s. s. by the unilateral spikelet disposition, the smooth surface of the upper anthecium, and a C₃ photosynthetic pathway. This new genus is described and compared with other allied genera of the Paniceae.

Abstract We examined populations of perennial, shrubby buckwheats in the Eriogonum corymbosum complex and related Eriogonum species in the subgenus Eucycla, to assess genetic affiliations of the recently named E. corymbosum var. nilesii. The known populations of this variety are all located in Clark County, Nevada, U. S. A. We compared AFLP profiles and chloroplast DNA sequences of plants sampled from populations of E. corymbosum var. nilesii with those of plants representing other E. corymbosum varieties and related Eriogonum species from Colorado, Utah, northern Arizona, and northern New Mexico. We found evidence of genetic cohesion among the Clark County populations as well as their genetic divergence from populations of other E. corymbosum varieties and species. The genetic component uncovered in this study supports the morphological findings upon which the nomenclatural change was based, attesting to the taxonomic distinctness of this biological entity.

We describe and illustrate the new species Fevillea anomalosperma from the semideciduous forests of northwestern Bolivia. Analysis of chloroplast DNA sequences representing most genera of Cucurbitaceae, including Fevillea with four of its seven species, supports placing the new species in Fevillea despite its small (10–11.5 × 7.5–10 mm, 2–3 mm thick), flattened, and highly sculptured seeds, which are unusual in the genus. The molecular phylogeny also revealed that the recent sinking of the monotypic genus Anisosperma into Fevillea is not justified.

Se ilustra y describe Fevillea anomalsperma, una nueva especie de los boques semi-deciduos del noroeste de Bolivia. Aunque las hojas y las flores son típicas de Fevillea, las semillas pequeñas (10–11.5 × 7.5–10 mm, 2–3 mm de grueso), aplanadas y muy esculpidas de esta nueva especie no lo son. La posición de esta nueva especie dentro de Fevillea ha sido apoyado por análisis filogenéticos de secuencias de ADN del cloroplasto, en los cuales se ha incluido representantes de la mayoría de los géneros de Cucurbitaceae, junto con quatro especies de Fevillea. Filogenia molecular demuestra que la inclusión del género monotípico Anisosperma en Fevillea no es justificada.

We describe a new species, Lotus lourdes-santiagoi (Leguminosae) of the L. angustissimus complex endemic to Andalusia (southwestern Spain). The most important diagnostic character of the new species is the presence of indumentum on the adaxial face of the standard. A table presents the distinguishing characteristics of the new species, comparing it with L. castellanus Boiss. & Reut, and L. palustris Willd., the two other species in the group having keeled beaks curved inwards at the tip.

A monograph of Castelnavia is presented. Phylogenetic analyses of morphological characters reveal eight nonhomoplasious synapomorphies supporting the monophyly of the genus: 1) absence of roots, a 2) unilocular mature, 3) anisolobous ovary that is 4) surrounded by stem tissue during and after anthesis, 5) horizontal at anthesis, with an 6) asymmetrically inflated pedicel apex and 7) longitudinal axis at 45–90° angle relative to pedicel axis, and 8) one deciduous capsule valve. Five species and two forms are recognized: Castelnavia fluitans, C. monandra, C. multipartita (C. m. forma multipartita, C. m. forma pendulosa C. T. Philbrick & C. P. Bove), C. noveloi, and C. princeps. Four species accepted by earlier authors are placed in synonymy. The morphology and ecology of the genus is discussed, and species descriptions, illustrations, a distribution map, lists of specimens examined, and a key to species are presented. Castelnavia occurs primarily in Brazil with one species in Bolivia. The greatest species diversity is in the Brazilian states of Mato Grosso, Pará, and Tocantins.

Two new species of Loeselia (Polemoniaceae) from central Mexico are described and illustrated. Both are known only from small areas in the Balsas Depression of the state of Michoacán. Loeselia tancitaroensis occurs in pine-oak forest on the foothills of Cerro Tancítaro. It is similar to the Oaxacan endemic L. ruprestis, from which it differs in possessing linear to linear-lanceolate inflorescence bracts, entire to rarely one-toothed floral bracts and sepals, shorter sepals and ovaries, and carpels with two ovules. Loeselia spectabilis is restricted to tropical deciduous forest in the Infiernillo region. It is distinguished from the closely related L. grandiflora by possessing petiolate leaves, shorter sepals, glandular-ciliate corolla margins, and carpels with a single ovule.

Phylogenetic relationships between and within Phacelia sections Whitlavia and Gymnobythus are inferred based on nuclear ribosomal DNA [5.8S, and flanking internal transcribed spacers (ITS) 1 and 2] and chloroplast DNA (rpl16 intron) sequences. These two sections share morphological characters and have been thought to be closely related. The purpose of this study is to test whether each of the two sections is monophyletic as well as whether they form sister clades. Our results indicate that section Gymnobythus is monophyletic, and members of section Whitlavia form two clades that correspond to subsections previously suggested by Gillett. In the ITS dataset, the two Whitlavia groups are not sister clades, but there is little support for their placement. The rpl16 and rpl16 ITS combined datasets provide resolution and strong support for monophyly of both sections. Both datasets indicate hybridization or a recent divergence between Phacelia parryi and Phacelia minor, as well as a close alliance between Phacelia longipes and Phacelia campanularia.

Understanding species limits in recent radiations is often difficult because sufficient time may not have elapsed since speciation to allow for the accumulation of unique species-specific traits. However, because population genetic markers evolve rapidly, patterns of genetic structure based on these markers can often discern genetically isolated population groups, even when other markers, such as DNA sequences, can not. In this study, we analyzed patterns of genetic structure based on microsatellites in Conradina and identified a group of plants in Dunns Creek State Park (Putnam County, Florida) that are genetically divergent from all other described Conradina species. We then carried out a morphological study that revealed several unique characters in these populations, most notably thin-walled unicellular hairs, epidermis features, and larger calyces. Because these populations are genetically and morphologically diagnosable from all other Conradina species, we thus consider them to be specifically distinct, and name this taxon Conradina cygniflora. Conradina cygniflora is endemic to Dunns Creek State Park in south-central Putnam County, Florida, where it occupies nine tightly-clustered sites that probably form around two to four self-sustaining populations. Due to its extremely limited geographic distribution and few individuals, we recommend that Conradina cygniflora be listed as federally endangered.

Mentheae is an economically important tribe in Lamiaceae with many ornamentals and culinary herbs. Although its monophyly is well supported by molecular data, the subtribal delimitation and the intergeneric relationships are still poorly understood. The nutlet morphology (SEM) of the tribe and the presence/absence of myxocarpy is documented here for 57 out of 65 genera in order to assess the systematic value of nutlet characters and to evaluate the existing molecular phylogenies for this group. Significant variation was found in nutlet shape, morphology of the abscission scar, distribution of trichomes, and surface sculpture. Five different surface types were recognized in Mentheae based on differences in cell outline, anticlinal walls, cell boundary relief, and curvature of the outer periclinal wall. Representative nutlet features proved to be phylogenetically informative in Mentheae mainly at the generic level. Cladistic analyses were performed based on 15 morphological nutlet characters and/or available molecular data (nuclear ribosomal ITS and chloroplast trnL-trnF spacer sequences). The resulting topologies indicate that the addition of nutlet characters to the DNA-data matrix improved the overall resolution and also increased bootstrap support values in comparison with exclusively molecular phylogenetic analyses. The evolution of major nutlet characters within the tribe Mentheae is discussed.

Verbenaceae tribe Verbeneae includes three major genera, Verbena, Glandularia, and Junellia, which form a recently diversified group. Junellia is a South American genus, whereas Verbena and Glandularia are distributed in temperate regions of both South and North America. Seven noncoding chloroplast regions were sequenced including intergenic spacers and/or introns in trnD-trnT, trnS-trnG, trnS-trnfM, trnT-trnL, trnG, trnL, and trnL-trnF; the nuclear ITS and ETS regions were also sequenced. Together with previous studies, these results suggest that Junellia, as traditionally conceived, is a paraphyletic group of two separate clades. Junellia should be restricted to the clade containing the type, J. micrantha, which also includes Glandularia subgenus Paraglandularia and the genus Urbania. Consequently Urbania and Glandularia subgenus Paraglandularia are reduced to synonymy under Junellia, and eight new combinations in Junellia are proposed: Junellia ballsii, J. crithmifolia, J. fasciculata, J. hookeriana, J. lucanensis, J. occulta, J. pappigera and J. origenes. The remaining Junellia species form a monophyletic group here designated as the new genus Mulguraea, with 13 new combinations: Mulguraea arequipense, M. asparagoides, M. aspera var. aspera, M. aspera var. longidentata, M. cedroides, M. cinerascens, M. echegarayi, M. hystrix, M. ligustrina var. ligustrina, M. ligustrina var. lorentzii, M. scoparia, M. tetragonocalyx and M. tridens. Verbena and Glandularia s. s. are both monophyletic based on ETS/ITS data, but neither is monophyletic based on cpDNA data. Relationships within each genus are still not wholly resolved, nevertheless there is evidence that South and North American Verbena might both be monophyletic. Verbena and Glandularia are sister groups, and together they are sister to the reconstituted Junellia. Mulguraea is sister to the group comprising all the three genera, Verbena, Glandularia, and Junellia.

The salt marsh dodders, Cuscuta salina, have been historically delimited as a morphologically variable assemblage of inbreeding forms that parasitize hosts growing in alkaline or saline habitats from western North America. This morphological diversity has been traditionally classified into three varieties: salina, major, and papillata. A morphometric analysis of floral characters and a molecular study using both plastid and nuclear DNA sequences strongly support the segregation of a new species, Cuscuta pacifica Costea and M. A. R. Wright, from C. salina. The new species corresponds to a lineage that includes varieties major and papillata, whereas C. salina is limited essentially to its type variety. Cuscuta pacifica and C. salina are sister species that have only a small area of parapatry in lower California, where they are ecologically and reproductively separated. Cuscuta salina occurs mostly in inland vernal pools and salt flats of Arizona, California, Nevada, Utah, Baja California, and Sonora, and grows primarily on Frankenia and Suaeda. Cuscuta pacifica can be found in salt marshes from the southcentral Pacific coast of California north into British Columbia, parasitic especially on Salicornia and Jaumea carnosa. Cuscuta salina var. papillata (Yunck.) Costea and M. A. R. Wright, parasitic on hosts that grow in coastal interdunes, falls within the range of variation of C. pacifica, where it is transferred.

The identification of plastid DNA markers that provide sufficient phylogenetic resolution at the species and population levels is an important challenge for plant systematics. This is mainly due to the relatively slow rate of evolution of the plastid genome. In this study, we examine the utility of several plastid DNA regions for phylogenetic inference at low taxonomic levels in tribe Lycieae (Solanaceae). The regions employed here previously provided considerable numbers of potentially informative characters in investigations of sequence variation across the plastid genome, and one region (trnH-psbA) has been advocated for use in DNA barcoding. We sequenced nine noncoding plastid DNA regions (∼8,400 bp) for a diverse sample of Lycium species and Phrodus microphyllus (tribe Lycieae), as well as the outgroup Nolana, and included published sequences from the distant outgroup Atropa. The nine regions varied with regard to their phylogenetic utility, as measured by the numbers of variable and parsimony informative characters and informative insertions/deletions. We advocate a combination of three regions, including trnD^GUC—trnT^GGU, rpl32—trnL^UAG, and ndhF—rpl32, for phylogenetic studies at the infrageneric or tribal level in Solanaceae. Collectively, these three plastid DNA regions had >100 variable characters across 24 taxa, with 72 parsimony informative characters, and 10 phylogenetically informative indels. Future studies should explore these three noncoding markers for low level phylogenetic questions in other taxonomic groups.

The phylogenetic relationships of six out of seven genera from the informal Hinterhubera group (Hinterhuberinae) and nine other subtribes in tribe Astereae primarily with Southern Hemisphere distributions were studied using internal and external transcribed spacer region nuclear DNA (ITS and ETS) sequence data. Bayesian and parsimony analyses were conducted on both datasets, independently and combined. Topologies resulting from the ITS and combined data sets were highly congruent, while the ETS based phylogenies were poorly resolved, probably because the characters are fewer and less informative. The monophyly of the Hinterhubera group was not confirmed, nor were the monophyly of the subtribes Podocominae, Lagenophorinae, Grangeinae, and Asterinae as delimited by Nesom and Robinson. Instead, our results suggest a closer relationship among the taxa from similar geographic areas. Within the Hinterhubera group, the monophyly of the genera has been confirmed. Westoniella was sister to Laennecia (Podocominae), while Hinterhubera was sister to Laestadia and Blakiella. The radiate Diplostephium and Guynesomia were disparately placed in the southern hemisphere clade and not related to the other radiate genera of Hinterhuberinae. Present analyses suggest that dioecy in Aztecaster and Baccharidinae evolved independently as hypothesized by Nesom. Archibaccharis (Baccharidinae) was sister to Plagiocheilus (Grangeinae). The analyses of ITS and ETS data, and Bayesian analysis of the combined dataset, resolved Baccharidinae as non monophyletic. Constraint analyses forcing a monophyletic Baccharidinae, with Plagiocheilus sister to Archibaccharis, did not reject monophyly of the subtribe.

Specimens of Villarsia cambodiana (Menyanthaceae), the only tropical Villarsia species, were collected from Vietnam, where the species had not been recorded. Molecular data were used to evaluate the phylogenetic position of V. cambodiana relative to 31 other Menyanthaceae taxa representing 11 species of Nymphoides and every species of Liparophyllum, Menyanthes, Nephrophyllidium, Ornduffia, and Villarsia. Phylogenetic analysis of nuclear (ITS) and chloroplast (matK/trnK, rbcL) DNA data strongly supported the resolution of V. cambodiana within Nymphoides, sister to N. aurantiaca. After plotting morphological data onto the molecular phylogenetic tree, we observed that leaf and inflorescence characters associated with an erect habit, which superficially would assign V. cambodiana to Villarsia, have arisen or been lost independently in several other Menyanthaceae species representing three genera. Moreover, several characteristics of this taxon, particularly seed morphology and an inflorescence with paired pedicels, are more consistent with those of Nymphoides than of Villarsia. We thus transfer V. cambodiana to Nymphoides under the new combination Nymphoides cambodiana.