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Using previously preserved material, a minimal number of sacrificed specimens, unharmed live individuals, and field observations, we studied the life history and habitat of the Pigeon Mountain salamander (Plethodon petraeus). Individuals of this species are patchily distributed among various habitats including rock outcrops and cave entrances. They were most abundant relative to other species of salamanders where extensive outcrops were associated with cave openings. Females mature at a larger size (mininum of 65 mm SVL) than males (minimum of 56 mm) and grow to a greater maximum size (85 mm for females and 80 mm for males). The minimum age at maturity appears to be three years for males. Our data on testicular variation suggest that mating occurs during late winter and/or spring.
Tipularia discolor is a terrestrial woodland orchid of the eastern United States that exhibits variable spatial patterns. The genetic diversity of several populations in Maryland, Delaware, and Virginia was examined using ISSR markers. Low levels of genetic variation were detected, yet four distinct genotypes were determined. A Mantel test revealed that genetic diversity did not correlate with spatial distance (Mantel t-test = −0.349; p = 0.364). An Analysis of Molecular Variance (AMOVA) showed genetic differences between and within populations (p = <0.01). Our data suggest that gene flow has occurred between the four populations of Tipularia discolor, although field studies have documented that populations are maintained through clonal growth. This study illustrates that ISSR markers can be used to detect genetic diversity at a population level.
Few studies have attempted to quantify the association between land snail communities and calcium (Ca) in upper soil horizons. If soil Ca is important to land snails, then land snail communities may be sensitive to reductions in soil Ca, including those caused by atmospheric acid deposition. In this study, snail density was estimated at ten 200m2 plots in mature forest using a litter sieving technique, and species richness was determined from litter sieving and timed searches. The most abundant snail species was the small spot, Punctum minutissimum (I. Lea), representing 34% of the specimens collected. Land snail density and species richness were positively correlated with extractable Ca, water soluble Ca, and pH in the Oe soil horizon and in the horizon below. Basal area of sugar maple, Acer saccharum Marsh., was positively associated with snail density and Ca in the Oe horizon, while basal area of red maple, Acer rubrum L., was negatively associated with snail density and Ca in the Oe horizon.
The Pike County Pocosin Nature Preserve is located approximately 10 km east of Troy, Alabama, on the east side of Walnut Creek. The Preserve consists of 84 hectares of xeric sandy ridges interrupted by deep ravines. The Alabama Department of Conservation and Natural Resources manages the site with an emphasis on the protection of rare species. The floristic survey was conducted from March 1999 through September 2000. A total of 348 taxa representing 247 genera and 97 families were found to occur or were reported from within the Nature Preserve. Poaceae represented the largest family with 43 species. Asteraceae and Fabaceae were the next largest families with 40 and 31 species, respectively. Quercus represented the largest genus with 12 taxa.
Migrating monarch butterflies can be censused several ways, but studies that compare censusing methods are lacking. Furthermore, although it is known that monarch butterflies alter their flight strategies in varying wind conditions, it is not known if and how counts of monarchs made during migration are affected by wind conditions. We assessed the abundance of migrating monarchs in the fall of 2000 using three techniques, which each differ in the flight strategy they target. We tested for differences between the resulting counts and examined the influence of wind conditions on each method. We (1) censused monarchs on a five mile driving route, (2) counted monarchs from a hawkwatching platform, and (3) counted monarchs at a roost site. The hawkwatch and driving census produced similar overall indices of abundance. Furthermore, wind conditions affected each count. As we predicted, the driving census detected the most monarchs when wind speeds and directions were unfavorable for migration, and the most were counted with the hawkwatch census during light favorable wind directions. Unexpectedly, counts of roosting monarchs were highest during strong winds in both favorable and unfavorable directions. We recommend that long-term monarch monitoring stations employ a combination of techniques to obtain comparable counts of monarchs.
Although many surveys of invasive plants have been conducted, relatively little research has been conducted on the biology of hybridization between invasive and native species. We hypothesized that interspecific hybridizations between the native bittersweet (Celastrus scandens L.) and the invasive introduced species (C. orbiculatus Thunb.) may be more vigorous and have less seed dormancy than C. scandens seedlings. To test this hypothesis, we performed controlled pollinations using C. scandens as the female parent and C. scandens or C. orbiculatus as the male parent. Although both the interspecific and intraspecific pollinations resulted in a comparable percentage of germinating seedlings, the seedlings from the interspecific crosses had less seed dormancy and were more vigorous than the intraspecific seedlings. These results indicate that the decline of the American bittersweet may be due in part to interspecific hybridizations with the invasive introduced species, and that the distinct genetic identity of C. scandens may be threatened.
Since receiving legal protection in 1972, Maryland's black bear (Ursus americanus Pallas) population has grown, and increased numbers of bear-human conflicts created a need for information on bears for management. Thus, we determined habitat use of female black bears in western Maryland by incorporating locations (n = 641) of 5 adult radio-collared bears into a geographical information system (GIS) to enable analyses of macro-habitat characteristics. Overall, bears selected mixed forest and wetlands, and habitat with high stream densities. Bears selected conifer stands throughout the year and residential areas during the spring-summer season. Variation in use of residential areas and habitat near streams appeared to be related to the availability of wetlands to individual bears. Bears avoided primary highways, but not other road classes, although females traveling with cubs selected habitat at lower road densities. To manage habitat for female black bears, we suggest maintaining wetlands and mixed forest habitats, enhancing understory cover in maturing deciduous forest, increasing conifer stands in areas where management for mature forest is unrealistic, and constructing wildlife underpasses on high-speed highways.
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