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Rich Montane Seeps are rare wetland communities endemic to high elevations of the southern Appalachian Mountains. Comprehensive data on the flora and fauna associated with these communities are lacking. Recent surveys indicate the rooting by nonnative wild pigs (Sus scrofa) may be affecting these communities. This study describes the abiotic and biotic features of Rich Montane Seeps across the Great Smoky Mountains National Park (GSMNP), investigates the effects of wild pigs on plant and salamander communities, and examines habitat attributes that influence pig disturbance. In our study a Rich Montane Seep was defined as any wetland with sheet flow occurring in hardwood forests above 1067 m. Pig disturbance and habitat attributes were measured in 1-m2 plots placed at 5 m intervals along a transect located on the longest axis of each seep. Habitat attributes measured included plant cover, plant richness, surface water, substrate, down woody debris, and shrub and tree densities (sampled in 3 m diameter circular plots). Salamanders were also sampled in each 1-m2 plot, identified to species when possible, and classified as larva, juvenile or adult. Thirty-five seeps, representing 24 drainages, were sampled. Rich Montane Seeps were characterized as small, linear wetlands with an open canopy, dense herbaceous vegetation, and few trees or shrubs. One hundred eighty species of plants (132 herbs, 35 shrubs, and 13 trees) and 10 species of salamanders (97 adults, 204 juveniles, 14 larvae) occurred in seeps, including eight plant species and three salamander species of conservation concern. Forty-nine percent of seeps and 54% of drainages had evidence of pig disturbance. Disturbance within seeps varied from 0-96% (mean = 21%). Wild pigs negatively affected plant cover and plant richness. Wild pigs also had a negative effect on salamander surface density, but to a lesser extent than on plants. Amount of pig disturbance was negatively associated with slope. These results strongly suggest wild pigs are threatening the ecological integrity of Rich Montane Seeps across their range by negatively affecting the plant and salamander communities, particularly in seeps occurring on flat terrain.
As urban habitats vary in composition and structure along the urban to rural gradient, different degrees of urbanization likely result in a diversity of landscape responses from wildlife. We investigated this relationship with the Virginia opossum (Didelphis virginiana), an urban adapted species that is both common and understudied in highly metropolitan landscapes. We investigated which landscape factors affect opossum occupancy, colonization, extinction, and detection by using a large system of motion-triggered camera traps in the Chicago metropolitan area over 10 seasons from spring 2010 to summer 2012. Opossum patch occupancy rates were highest near natural water sources regardless of urbanization, whereas occupancy rates in patches ≥1000 m from natural water sources decreased with increasing urbanization. Our results suggest opossums have relaxed habitat needs at intermediate levels of disturbance, as the ability to locate anthropogenic water sources may allow them to occupy previously uninhabitable patches.
Black-crowned Night-Herons (BCNH; Nycticorax nycticorax) increasingly colonize urban areas, demonstrating they consider the value of such habitat to outweigh the risks. However it is unclear if cities support reproductively successful populations of BCNH. To begin to address this question, I evaluated if a park in Chicago, Illinois, provided suitable breeding habitat or was an ecological trap for a colony of approximately 400 BCNH. Nest densities were 217 nests/ha in 2010 and 315 nests/ha in 2011, which were higher than nest densities observed in North American BCNH colonies in natural habitats. Ratios of young to active nests were 1.22 in 2010 and 0.76 in 2011, similar to ratios observed in nearby BCNH colonies. Within the park BCNH selected between two neighboring habitat patches. Logistic regression was used to predict habitat patch selection as a function of colony size and year. In the model the probability of selecting a larger, more exposed habitat patch versus a smaller, more secluded habitat patch, increased with colony size. This trend in habitat patch selection demonstrated behavioral flexibility which may have facilitated successful colonization of a human-modified landscape. The findings support the conclusion that in 2010 and 2011, an urban park in Chicago supported a locally endangered BCNH population and was not an ecological trap.
Male anuran (frog and toad) advertisement calls associate with fitness and can respond to environmental cues such as rain and air temperature. Moonlight is thought to generally decrease call behaviors – perhaps as a response to increased perceived risk of predation – and this study sought to determine if artificial lighting produces a similar pattern. Using a handheld spotlight, light was experimentally introduced to natural anuran communities in ponds and streams. Custom call surveys where then used to measure anuran calls in paired unlit and lit conditions at six locations in central Texas. Among seven species heard, the number of frogs calling and call index declined in response to the acute light input. Local weather conditions could not explain differences between numbers of frogs calling between species, sites, survey order, or lighting order suggesting the main effect on number calling was light treatment. It appears acute artificial light alone can change calling behavior within several species in natural, mixed species assemblages.
The emydid turtle genus Graptemys is characterized by intra- and interspecific dietary diversity. Sympatric species pairs typically differ in trophic morphology and dependence on bivalve mollusks in female diets, yet there is a lack of comprehensive comparisons of the diets of sympatric species. I collected feces from 92 black-knobbed sawbacks (G. nigrinoda) and 54 Alabama map turtles (G. pulchra) from the Alabama River at a site in Autauga and Lowndes counties, Alabama. Samples were analyzed separately for unsexed juveniles, adult males, juvenile females larger than the smallest mature males, and adult females of each species. Sponges, aquatic insects (particularly caddisfly larvae), and filamentous algae were the primary foods of G. nigrinoda. Native mussels, invasive Asian clams, and aquatic insects (but few caddisfly larvae) were the primary foods of G. pulchra. Each of the four sex and size classes exhibited substantially greater similarity with conspecific classes than with classes of the other species. Intraspecific interclass similarity in diet showed size-structured patterns in both species but with opposite patterns. In G. nigrinoda the classes that were most similar in diet were the smallest-bodied classes, unsexed juveniles and adult males, which fed most heavily on sponges; the largest-bodied class, adult females, fed most heavily on filamentous algae and was least similar in diet to other classes. In G. pulchra the classes that were most similar in diet were the two largest-bodied classes, adult and juvenile females, which fed most heavily on bivalve mollusks; the smallest-bodied class, unsexed juveniles, was least similar in diet to other classes. These results reinforce the importance of body size in determining Graptemys diets and suggest dietary differentiation of sympatric Graptemys species may extend beyond differentiation in adult females more often than is generally thought.
This study examined predation risk for juvenile native fish between two riverine shoreline habitats, backwater and debris fan, across three discrete turbidity levels (low, intermediate, high) to understand environmental risks associated with habitat use in a section of the Colorado River in Grand Canyon, AZ. Inferences are particularly important to juvenile native fish, including the federally endangered humpback chub Gila cypha. This species uses a variety of habitats including backwaters which are often considered important rearing areas. Densities of two likely predators, adult rainbow trout Oncorhynchus mykiss and adult humpback chub, were estimated between habitats using binomial mixture models to examine whether higher predator density was associated with patterns of predation risk. Tethering experiments were used to quantify relative predation risk between habitats and turbidity conditions. Under low and intermediate turbidity conditions, debris fan habitat showed higher relative predation risk compared to backwaters. In both habitats the highest predation risk was observed during intermediate turbidity conditions. Density of likely predators did not significantly differ between these habitats. This information can help managers in Grand Canyon weigh flow policy options designed to increase backwater availability or extant turbidity conditions.
The genus Dionda consists of at least 12 species, of which most inhabit spring-dominated streams within the western Gulf slope drainages of North America and demonstrate some differences in habitat selection within these systems. The purpose of this study was to assess the influence of stenothermal spring or eurythermal stream habitat selection on the life history strategies of the stream-associated Dionda argentosa, a population of Dionda diaboli restricted to the spring influenced portions of Pinto Creek (Kinney County, Texas), and a population of D. diaboli utilizing stream habitats in the Devils River (Val Verde County, Texas). While differences in spawning seasons between the two species were noted, all three populations displayed life histories characteristic of opportunistic strategists including early maturation, long spawning seasons, production of multiple batches of oocytes, and short lifespans (<3 y). Differences in reproductive season between the spring- and stream-associated Dionda were consistent with the hypothesis stenothermal waters of springs lack terminating cues to induce gonadal quiescence in fishes.
Charles Darwin first suggested some carnivorous plants attract insects to their leaves for extracting nutrients. Since Darwin, it has been assumed that the ability to lure prey is a characteristic of botanical carnivory and that there is strong selection for carnivorous plants to evolve adaptations to accomplish this. The carnivorous syndrome defines botanical carnivory as having four components that include the ability to: attract prey, retain prey with specialized leaves, dissolve prey with digestive enzymes, and absorb soluble nutrients from prey. Relatively few studies have investigated prey attraction and it has been well documented in only three genera of carnivorous plants. We conducted a series of field and lab experiments on the dwarf sundew (Drosera brevifolia) and found this species to be no better at capturing prey than neutral sticky traps. Thus, no evidence was found suggesting this species lures prey to its leaves. We suggest that, like spider webs, sundews might be better adapted to having adhesive surfaces that passively capture prey. Carnivorous plants face the prey-pollinator conflict of trying to draw the same insects to flowers for pollination as are being drawn to leaves as prey. By evolving alternative ways of capturing prey without attractants, some taxa of carnivorous plants, like D. brevifolia, may reduce the intensity of the prey-pollinator conflict. If these alternatives prevail in species-rich genera of carnivorous plant, then the carnivorous syndrome may need to be refined.
Helenium virginicum is a narrowly endemic federally protected species, disjunct between Virginia and Missouri. To study the magnitude and distribution of genetic diversity within this species, we determined ISSR fingerprints and cpDNA haplotypes of plants in nine Virginia and eight Missouri populations. We found high ISSR diversity at the species level, with higher diversity in Virginia than Missouri. Additionally, moderately low diversity at the population level and high population structure suggests low gene flow among populations. Mean divergence between Virginia and Missouri populations was greater than between populations in either region. Missouri populations were more structured than Virginia populations. We found six distinct cpDNA haplotypes distributed among H. virginicum populations, with one found in both regions, two only in Virginia, and three only in Missouri. High genetic divergence among populations and between regions, the demographic asynchrony of populations, and self-incompatibility of the species suggest that clusters of populations in Missouri and Virginia be protected. These data will assist federal and state agencies deciding whether to delist and how to manage this species.
Populations of the endangered giant kangaroo rat (Dipodomys ingens) have decreased because of habitat fragmentation and isolation over the past 100 y. Changes in population structure due to habitat fragmentation can significantly affect the population size and the dispersal of these animals compromising long-term sustainability of each fragmented population. We collected small ear clippings from male and female giant kangaroo rats from six sites in the southern San Joaquin Valley to determine the genetic population structure of this species in this part of their range. Multilocus F-statistics indicated that the six populations of giant kangaroo rat are not composed of randomly mating populations and that genetic drift and inbreeding are major determinants of population structure. Furthermore, F-statistics confirmed a significant decrease in observed heterozygosity. Genetic distance analyses did not support the hypothesis that geographically distant populations would exhibit greater genetic differentiation. We also compared our data to published estimates of genetic diversity of giant kangaroo rats in populations to the west and north, the other large population centers of this species.
Scaling studies on phenotypic characteristics like birth mass are useful to understanding life history attributes within species. The wide range in body mass of elk (Cervus elaphus) in North America and Europe allows robust estimation of scaling relationships. Our goal was to estimate the scaling relationship of maternal body mass and offspring birth mass. Data were extracted from the literature, which included captive elk fed a readily digestible diet rich in nutrients. The mass of the mother at birth and the birth mass of the young were recorded for 11 groups of mothers and their offspring. A simple linear regression was used to estimate an allometric relationship between maternal body mass and offspring birth mass (R2 = 0.90). Birth mass scaled to the 0.78 power of maternal body mass. Understanding scaling relationships affecting maternal investment might have implications for understanding body size variation across the geographic range of elk.
Understanding demographic structures of populations allows managers to better evaluate factors affecting populations and increase efficiency of conservation efforts. Recent studies suggest low productivity, but high survival characterizes mallard (Anas platyrhnchos) populations in the Nebraska Sandhills. We studied age ratios of decoy-trapped and observer-shot mallards in the Sandhills during 2007–2008. Observed age distribution (second-year:after-second-year) of mallards was 2.8:1 for females and 0.8:1 for males. Age ratios of trapped females were skewed towards young females relative to other studies, and the age ratio of trapped females was not different than the age ratio of the sample we collected by shooting. The skewed age ratios we observed provide additional context to the low reproductive success that has been reported for nesting mallards in the Sandhills. Second-year mallard females tend to invest fewer resources and take fewer risks associated with nesting. As a result the Sandhills population may not contribute significantly to productivity of the continental mallard population but act as a reservoir of young female mallards available to disperse to more productive breeding areas in future years.
We evaluated the effect of arthropod presence on the growth of Tillandsia violacea in a Quercus spp.-Abies religiosa forest in Hidalgo, Mexico. We used 40 T. violacea individuals (<20 cm in diameter) attached to Quercus spp. trees. Insecticide was sprayed weekly on 20 plants during 1 y, another set of 20 plants located 100 m away were not sprayed. Both leaf number (N) and length (L) were recorded every 2 mo, and the foliar load was obtained. We found lower leaf production, leaf length, and foliar load in plants sprayed with insecticide than in nonsprayed plants. Our results show arthropod presence increases plant growth. We suggest this is due to the fragmentation activity of arthropods on litter, which promotes the decomposition process of the organic matter accumulated in epiphytes and increases nutrient release to the plant.