The Federal threatened eastern prairie fringed orchid (Platanthera leucophaea) occupies prairies, sedge meadows, bogs and fens, primarily north of the Wisconsinan glacial boundary. In the Midwest, where restoration is a recovery objective, its southern distribution is thought to be limited by the transition from nutrient-rich Wisconsinan-aged soils to more acidic nutrient poor soils of Illinoian-aged glacial drift. To better understand edaphic factors affecting its distribution and potential for establishment of new populations, we analyzed soil characteristics across the range of habitats occupied by this species, as well as from unoccupied habitats on the Illinoian Till Plain. We found that P. leucophaea occupies a complex edaphic gradient in variation of % organic matter, base content and soil texture. On Wisconsinan-aged substrates, it occurs in circum-neutral base-rich organic prairie soils in Illinois and Wisconsin and in less calcareous soils with slightly higher pH and lower organic matter content in Michigan lake plain prairies. Eastern sand prairie and sedge meadow habitats on Wisconsinan-aged drift and on unglaciated soils are moderately acid and nutrient poor, while bog and fen habitats are more strongly acidic and highly organic, with no evidence for an underlying calcareous substrate. In comparison, unoccupied prairie soils on the Illinoian till plain have lower pH, % organic matter and base concentrations. These soils also have relatively high % silt content which results in comparatively low available soil moisture holding capacity. This combination of soil conditions may exceed the tolerance limits of P. leucophaea and prevent this species from occurring south of the Wisconsin glacial boundary in the Midwest. On the other extreme, calcareous fens have high pH levels as well as extremely high calcium concentrations, which may exceed the tolerance limits of this species. These findings have implications for guiding efforts to establish P. leucophaea into habitats that should be suitable for this species.

Seed predation has the potential to strongly reduce seed production and thereby act as a selective force on the evolution of flowering traits and other defenses against herbivory. We characterized levels of predispersal seed predation on Hibiscus moscheutos (Malvaceae) during 2001 and 2002 at four sites in Ohio and Maryland, USA. The seed predators were a weevil, Conotrachelus fissinguis (Coleoptera, Curculionidae) and a bruchid beetle, Althaeus hibisci (Coleoptera, Bruchidae). The weevil occurred at three of the four sites and damaged 24% to 94% of fruits in these populations. The bruchid occurred at all four sites, where it destroyed 4% to 27% of the seeds. Seed predation varied between years and among sites for both predators and year-by-site interactions were common. Variation in predation levels indicates that seed predators did not influence this species uniformly, but they were often abundant and sometimes destroyed nearly all of the seeds produced. At one of the Ohio sites, we assessed levels of seed predation at 5-d intervals during the 2001 flowering season. At this population, bruchid damage was greatest for seeds produced by flowers that opened in late July, when flowers were scarce, whereas weevil damage was greatest in mid-August and coincided with peak flowering. The timing and greater extent of weevil damage suggest that they may have a greater effect on plant fitness than bruchids.

The interactions between keystone species and ecosystem engineers may have important community-level consequences. We studied the effects of a keystone species, the aphid-tending ant (Formica obscuripes), on the abundance of engineered leaf shelters, the levels of herbivory on leaf tissue and the structure of arthropod communities within leaf shelters on Hooker's willow (Salix hookeriana) in a coastal dune ecosystem in northern California. Leaf shelters on branches with aphid-tending ants had 54% more individuals than shelters on branches without ants, possibly because shelters are used as a refuge from predation. Levels of herbivory were 2× greater on branches without aphid-tending ants than branches with ants. Our study suggests that aphid-tending ants may actually increase the abundance of arthropods at small spatial scales within leaf rolls while simultaneously reducing rates of herbivory at the branch level.

A study was conducted to evaluate the effect of a pulsing hydrology on the productivity and nutrient uptake of an herbaceous riverine wetland. Pulsing effects were evaluated using 20 0.9-m² wetland mesocosms: 10 planted with Schoenoplectus tabernaemontani (C.C. Gmel) Palla and the other 10 planted with Typha angustifolia L. For each species, half the mesocosms were subjected to a 3-mo pulsing regime while the others were subjected to steady-flow conditions. Hydrology parameters were selected to approximate a pulsing experiment being carried out concurrently at two 1-ha wetlands at the research site. Typha wetlands were significantly more productive than Schoenoplectus wetlands; however no significant differences in productivity or morphology were observed between pulsed or steady-flow wetlands among species groups. No significant differences in nutrient concentrations, uptake or uptake efficiency were detected among species groups either, however hydrology did influence plant tissue N:P ratios. For all wetland mesocosms, the mean N:P ratio was 9.2 ± 0.6 for steady flow wetlands and 11.7 ± 0.5 for pulsed, suggesting that the steady flow wetlands were more N limited than pulsed wetlands. The potential applications and limitations of applying these results to the 1-ha wetlands study are discussed.

The influence of environmental factors on Juniperus seedling growth and mortality in Juniperus woodlands and their role in community replacement or succession is poorly understood. A full factorial field experiment was set up to investigate the influence of adult tree canopies, light levels and water and nutrient additions on Juniperus ashei seedling growth and mortality. Relative growth rates calculated from basal diameter, height and number of seedling branches were used as response variables in a four- way multivariate analysis of variance, using canopy, light levels, water and nutrient manipulations as factors. The pattern of seedling growth in the experiment was best explained with two significant three- way interactions between the canopy, light level and water treatments (F = 2.21, P = 0.04) and light level, water and nutrient treatments (F = 3.01, P = 0.03). Greatest seedling relative growth rates occurred with modified light levels associated with canopies removed, with supplemental water and nutrients. Mortality was increased by shading with supplemental water, added nutrients or a combination of supplemental water and nutrients. Conversely, mortality was not affected by canopy treatment, but it was reduced with high light levels, the additions of nutrients, water or combinations of nutrients and water. Evidence suggests that growth of J. ashei seedlings and eventual replacement of the adults is most strongly influenced by light levels, and at higher light levels, both water and nutrients interact to support continued growth.

The Illinois River Valley (IRV) is a critical ecoregion for migratory waterfowl. Significant wetland loss occurred in this region in the early 20^th Century, and remaining wetlands are subject to additional degradation via sedimentation, summer flooding from the Illinois River and invasive species. Managed moist-soil wetlands may provide quality foraging habitat for migrating waterfowl, but contemporary estimates of seed production and carrying capacity do not exist for the IRV. We evaluated seed production and carrying capacity of a 931-ha moist-soil wetland at Chautauqua National Wildlife Refuge in central Illinois during falls 1999–2001. Seed production varied annually (329–1231 kg/ha), but overall was greater than previously published estimates for other areas of North America. Estimated carrying capacity across years was 6.760 ± 411 (se) duck use-days/ha; this value was 1.5–15.4 times greater than other published carrying capacity estimates for harvested corn, rice and soybeans. We recommend continued regional-scale research to estimate foraging carrying capacity of moist-soil wetlands for waterfowl in mid-latitude regions, such as the IRV or upper Mississippi River.

Leafy spurge (Euphorbia esula) is an exotic, perennial, invasive weed in many areas of the northern United States and Canada. There are many instances in pastures and wildlands where individual or small clusters of leafy spurge plants are distant and upslope from larger patches, and wildlife have been suspected as seed dispersal agents. Wildlife can disperse seeds by ingestion then excretion of seeds in their feces. Fecal deposits of free-ranging deer (Odocoileus hemionus and O. virginianus; n = 176), sharp-tailed grouse (Tympanuchus phasianellus; n = 201) and wild turkeys (Meleagris gallopavo; n = 206) were collected during a summer in Theodore Roosevelt National Park (TRNP) in western North Dakota, and for deer only in Medicine Lake National Wildlife Refuge (MLNWR) in northeastern Montana. Feces were analyzed for the presence of leafy spurge seeds and any seeds found were tested for germinability and viability. Only one intact leafy spurge seed was found in one grouse fecal deposit and it was not viable. No leafy spurge seed was found in turkey feces. Two seeds that appeared to be immature leafy spurge seeds were found in one deer fecal deposit in TRNP, but neither seed was viable. One leafy spurge seed was found in each of four deer fecal deposits from MLNWR, but only one seed was viable and germinated. Seed-feeding trials with captive deer (n = 4), sharp-tailed grouse (n = 4) and wild turkeys (n = 4) were conducted to determine how leafy spurge seeds interact with the digestive systems of these animals. The only viable seeds defecated by grouse and turkeys were seeds excreted one day after ingestion. Two turkeys did not excrete any leafy spurge seeds and only a few viable seeds were defecated by the other two. One grouse defecated a larger number of viable seeds, but the other three grouse excreted only a few. Deer defecated viable seeds each of 4 d after ingesting them with most viable seed excreted on the first 2 d. These findings, along with those for the free-ranging animals, indicate that wild turkeys probably do not disperse leafy spurge seed while sharp-tailed grouse and deer may do so on a limited basis.

The Mammoth Spring crayfish (Orconectes marchandi) is listed as endangered by the American Fisheries Society's Endangered Species Committee and globally impaired by the Missouri Natural Heritage Database. Recorded at only three locations in the Spring River watershed (southern Missouri and northern Arkansas), little information exists on its range, associations with other crayfish and habitat selection. We sampled stream-dwelling crayfish with kicknets and quadrat samplers during spring-summer over 2 y in the Spring River drainage to determine distribution, relative density, habitat use, species associations, and life history characteristics of O. marchandi and other associated crayfish species. Nine crayfish species were collected in the Spring River watershed including a previously unrecorded invasive species, O. neglectus chaenodactylus, that appears to have replaced the native O. eupunctus from a portion of the watershed where it was previously abundant. The known distribution of O. marchandi was expanded from three streams in three sub-watersheds to 20 streams in eight sub-watersheds. Orconectes marchandi was found mainly in smaller streams (order 1–3) in habitats consisting of slower moving, shallow water with gravel, pebble and cobble substrates. Oronectes marchandi was not significantly associated with any crayfish species by site. Orconectes eupunctus was found exclusively in the main-channel South Fork and Spring rivers. Current velocity, water depth and substrate were related to crayfish densities, but were crayfish species- and size-dependent. Growth rates differed among species with O. punctimanus showing the greatest growth in carapace length from winter to summer and O. marchandi showing the greatest increase in weight with carapace length. Sex ratios differed among crayfish species and by season. Additional research is needed to gain a better understanding of factors affecting habitat selection by crayfish species and to determine potential impacts of O. neglectus chaenodactylus on native populations.

Numerous anthropogenic and natural factors affect living organisms in nature. Anthropogenic factors include a wide array of contaminants and processes that alter the habitat on both local and global scales. For example, chlorofluorocarbons (CFCs) and other industrial gases contribute to the depletion of the earth's protective ozone layer, resulting in increased amounts of cell damaging ultraviolet-B (UV-B) radiation reaching the surface of the earth. Recent experiments provide evidence that increasing ambient levels of UV-B radiation harm many amphibian species. UV-B radiation can kill amphibians and can cause sublethal damage to them. However, most studies that have examined the effects of UV-B radiation on amphibians have focused on developing embryos. There is little information on how UV-B radiation affects amphibians at later stages of development. In experimental laboratory tests, we exposed one group of juvenile western toads (Bufo boreas) to full spectrum lighting with ambient levels of UV-B radiation and control toads to full spectrum lighting excluding most UV-B. Juvenile toads exposed to ambient levels of UV-B radiation showed significantly greater mortality rates compared with controls. These results add to a growing body of literature demonstrating that UV-B is harmful to amphibians. Furthermore, our results suggest that investigators should look at the effects of UV-B radiation on different life stages before making conclusions about the overall impact of UV-B on amphibians.

We studied nest-site fidelity (1995–2000) and nest predation (1997–2000), and nesting movements (1999–2000) in a population of Chrysemys picta marginata at Miller's Marsh on Beaver Island, Michigan. On average, turtles nested farther (mean = 122.3 m) from the marsh than turtles in previously studied populations, possibly because of the relatively large nesting areas (n = 5) of our study. Nest predation was 17.4% over all years and was independent of nest location (distance from water, road vs. field nests, nesting field). Many turtles showed nest-site fidelity between years in that they favored one or two nesting areas and had annual inter-nest distances (ID) that were positively skewed and significantly less (mean = 88.7 m) than IDs of randomly paired nests of different individuals. Radiotelemetry indicated that most turtles emerged during the mid-afternoon and nested during the evening hours. Nesting excursion duration averaged 11.6 h and 75% remained on land overnight after nesting. The use of terrestrial refugia before and after the nesting process presumably reflected thermal limitations on movements. When compared to turtles that nested relatively close to the marsh, turtles that nested relatively far from the marsh initiated nesting movements earlier in the day, had circuitous routes to and from the nest site and had relatively long nesting excursion duration. The location of an aquatic home range apparently influenced nest-site selection and fidelity in some individuals although other individuals nested relatively far from the aquatic home range.

To understand the selective pressures that have influenced the evolution and maintenance of parental care, it is necessary to assess the consequences and function(s) of specific behaviors. We used field and laboratory experiments to investigate possible fitness benefits and proximate functions of female nest attendance in marbled salamanders (Ambystoma opacum). In the first field experiment, nests at which females remained until flooding had higher hatching success than those without attendant females, but results were somewhat equivocal. In the second field experiment we used unattended eggs in artificial clutches randomly assigned to one of four treatment groups: eggs physically agitated to possibly reduce developmental malformations and/or fungal growth, eggs protected from predators, eggs moistened by addition of water and eggs in an unmanipulated control group. Clutches that were protected from predators had significantly higher hatching success than control, agitation and supplemental water groups. In the laboratory experiment, nests in which fungal infection was controlled had higher hatching success than those without sterilized substrates. Also, physical agitation and increased moisture did not confer higher hatching success when fungi were eliminated in the laboratory. Predation and fungal infections appear to decrease hatching success in this species, and female nest attendance may reduce these risks.

The mating season in the northern watersnake (Nerodia sipedon) occurs in the spring during vitellogenesis. Courtship and mating occur primarily in trees and bushes which overhang the water, but may also occur on the stream bank. Watersnakes access these basking/mating sites from the water. Thus, the terrestrial trailing of a female, typical of most of the snakes studied, cannot occur. Based on field observations, only about 10% of female N. sipedon are in estrus (attractive to males via pheromones) on days with appropriate temperatures from late April to mid-June. Females in estrus vary in attractiveness and receptivity to males. In field experiments, males are able to locate caged females apparently via volatile pheromones. We suggest that watersnake pheromones are heavy, volatile compounds that accumulate in the air above the surface of the water and that males climb branches and systematically search for females in the vicinity of pheromone concentrations. In addition to pheromones, males use other means to locate females including systematic searching of bushes and movement towards moving snakes. Courtship may last from several minutes to more than 2 h. Most courtships that occur late in the mating season do not result in copulation.

We surveyed 88 upland wetlands and 12 1-km river sections for amphibians in Theodore Roosevelt National Park, North Dakota, during 2001–2002 to gather baseline data for future monitoring efforts and to evaluate changes in the distribution of species. We compared our results to collections of herpetofauna made during 1920–1922, 1954 and 1978–1979. The boreal chorus frog (Pseudacris maculata) was the most common amphibian in upland wetlands, followed by the tiger salamander (Ambystoma tigrinum), Woodhouse's toad (Bufo woodhousii), northern leopard frog (Rana pipiens), plains spadefoot (Spea bombifrons) and the Great Plains toad (B. cognatus). Bufo woodhousii was the only species that bred in the river. Our records for reptiles are less complete than for amphibians but no losses from the community are evident. The herpetofauna in Theodore Roosevelt National Park seems unchanged during at least the last half-century and likely since 1920–1922.

Habitat loss and subsequent subdivision of remaining habitat patches are considered major threats to terrestrial animal populations in natural environments. Habitat loss normally results in reduced population numbers in remaining habitat patches, whereas isolation of habitat patches affects population dynamics among them. In this study, we examined the distribution of the eastern chipmunk (Tamias striatus) in farmland woodlots. We used the Random Sample Hypothesis as a theoretical starting point in the study. By using a standard protocol to trap chipmunks in woodlots, we expected to capture approximately the same number of individuals per woodlot independent of the size of the woodlot. We found that the probability of capturing chipmunks declined with increasing size and distance to the nearest woodlots. Such a decline in densities seemed to happen even in woodlots of less than 10 ha. Large and remote woodlots tended to be surrounded by corn fields. Measured habitat and landscape variables gave no indication as to which ecological processes might have accounted for the observed pattern. Ecological factors, such as species interactions within a woodlot and movement of individuals among woodlots, should be addressed more closely experimentally.

Cavity-roosting species of bats generally require patches of forest containing older timber, but such habitats have been reduced in the southeastern United States. Rafinesque's big-eared bat, Corynorhinus rafinesquii, is a rare species for which data on natural roosts in the Gulf Coastal Plain (where caves are largely absent) are scant. We used radiotelemetry to locate tree roosts of C. rafinesquii in southeastern Mississippi from August 2001 until August 2004. We captured and radiotagged 25 bats that led us to 14 trees. Corynorhinus rafinesquii used hollow Nyssa spp. and Magnolia grandiflora. Most of these trees were still alive, relatively large (mean DBH = 79.4 cm, mean height = 18.5 m), possessed cavities with openings not located at their bases and were located adjacent to streams or other bodies of water. When bats shifted roosts among different trees, these sites were usually located nearby (mean distance ≅ 360 m). Tree roosts were apparently rare within the study area, and C. rafinesquii showed roost fidelity to particular areas of forest. Six tree roosts were used by multiple individuals and several trees were reused within tracking sessions and among years.

Atypical acorn traits, such as multiseeded acorns, have frequently been reported in oaks (Genus: Quercus), yet there is disagreement over whether such traits are advantageous or selectively neutral. Squirrel embryo-excision behavior is one factor that has not previously been considered in discussions of these traits. Several tree squirrels are known to remove acorn embryos before caching them by notching acorns apically using their incisors. We hypothesized that atypical acorns could potentially be advantageous in environments where such embryo excision occurs. To test this, we conducted germination tests on whole acorns, squirrel-notched acorns and artificially-notched acorns for Quercus alba trees that produced either single-seeded or atypical acorns. Atypical acorns included both multiseeded acorns and acorns with non-apical embryos. Atypical acorns appear to confer a survival advantage following either squirrel or artificial notching. Trees producing such acorns had higher successful acorn germination following notching when compared to trees that produced only single-seeded acorns. For acorns that had been either notched by squirrels in the field or artificially-notched apically in the lab, only acorns from trees producing atypical acorns successfully produced shoots with plumules. These acorns were planted and developed into healthy single seedlings. We review the literature for reports of atypical acorn traits, specifically multiseeded acorns, and find that this trait has been reported for 14 species of oaks, across both oak subgenera in temperate and tropical regions. We argue that atypical acorns are advantageous for oaks, allowing escape from both insect and mammalian seed predators.

Introductions of non-indigenous species in ballast water are one of the greatest threats to freshwater and marine ecosystems worldwide. New approaches to reducing the release of organisms from ballast water are under consideration nationally and internationally. Unfortunately, the development of scientifically defensible policy for controlling introductions from ballast water has been retarded by the lack of relevant ecological theory and a shortage of information about the identity and numbers of organisms in ballast. Here, we present a novel quantitative approach to estimating the risk of species establishment by combining a model for population spread with known allometric correlations between body size and population growth rate for broad taxonomic categories. Our approach is applicable to sexually reproducing, planktonic taxonomic groups including ctenophores, cnidaria, arthropods, annelids, mollusks and (as an approximation) echinoderms and fishes. As expected, the allowable volume of ballast discharge depends strongly on the acceptable level of risk (which is a societal decision), the taxonomic group of concern and the characteristics of the receiving environment. For example, for a risk tolerance equivalent to establishment of one in one hundred introduced species, independent releases of untreated ballast water should not exceed around 50,000 metric tons. Because of differences in horizontal mixing in different environments, releases in harbors are more risky than releases in open water. These results provide quantitative guidelines that could immediately lower the risk of species invasion while other more permanent technological solutions are developed.

We document the first known occurrences of the Crystal Darter (Crystallaria asprella) in the middle Mississippi River (MMR). Two young-of-the-year specimens were collected, the first on 6 June 1998 at river mile (RM) 78 and the other on 9 June 2004 at RM 55. Both specimens were collected in side channels at depths of 1 m and 5.4 m, respectively.

While conducting a study of home range and habitat use of the eastern hognose snake (Heterodon platirhinos) in Southern Ontario, we observed both mating and nesting behaviors for this species. Here we describe the active excavation of oviposition sites by H. platirhinos; mating behavior, including multiple copulations of a single female with five males; and philopatry to specific nest sites by multiple individuals in successive years. As our study site is close to the northern limit of this species' range, nest sites may need to be carefully selected to provide a thermal regime warm enough to incubate the eggs. Mean nest temperatures in the field ranged from 23.4 to 26.1 C, while incubation periods ranged from 49 to 63 d.