462 research outputs found

    Landscape genetics reveal broad and fine‐scale population structure due to landscape features and climate history in the northern leopard frog (Rana pipiens) in North Dakota

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    Prehistoric climate and landscape features play large roles structuring wildlife populations. The amphibians of the northern Great Plains of North America present an opportunity to investigate how these factors affect colonization, migration, and current population genetic structure. This study used 11 microsatellite loci to genotype 1,230 northern leopard frogs (Rana pipiens) from 41 wetlands (30 samples/wetland) across North Dakota. Genetic structure of the sampled frogs was evaluated using Bayesian and multivariate clustering methods. All analyses produced concordant results, identifying a major east–west split between two R. pipiens population clusters separated by the Missouri River. Substructuring within the two major identified population clusters was also found. Spatial principal component analysis (sPCA) and variance partitioning analysis identified distance, river basins, and the Missouri River as the most important landscape factors differentiating R. pipiens populations across the state. Bayesian reconstruction of coalescence times suggested the major east– west split occurred ~13–18 kya during a period of glacial retreat in the northern Great Plains and substructuring largely occurred ~5–11 kya during a period of extreme drought cycles. A range‐wide species distribution model (SDM) for R. pipiens was developed and applied to prehistoric climate conditions during the Last Glacial Maximum (21 kya) and the mid‐Holocene (6 kya) from the CCSM4 climate model to identify potential refugia. The SDM indicated potential refugia existed in South Dakota or further south in Nebraska. The ancestral populations of R. pipiens in North Dakota may have inhabited these refugia, but more sampling outside the state is needed to reconstruct the route of colonization. Using microsatellite genotype data, this study determined that colonization from glacial refugia, drought dynamics in the northern Great Plains, and major rivers acting as barriers to gene flow were the defining forces shaping the regional population structure of R. pipiens in North Dakota

    Population Dynamics of Three Amphibian Species Across the Sheyenne National Grassland of Southeastern North Dakota

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    Concerns over worldwide declines of amphibians, including some to extinction, has increased the urgency for understanding how amphibians interact within local environments and across regional landscapes. Hypotheses for declines include anthropogenic destruction and fragmentation of amphibian habitat, introduction of exotic predators and competitors, increased ultraviolet (UV-B) irradiation, acid precipitation, environmental contamination by pollutants, harsh climatic conditions, over harvesting, and infectious disease. Three different types of models were developed for the northern leopard frog (Rana pipiens), gray tiger salamander (Ambystoma tigrinum diaboli), and gray tree frog (Hyla versicolor/chrysoscelis complex) populations inhabiting the Sheyenne National Grassland (SNG) in southeastern North Dakota. The SNG is a relatively large (283 km2) and contiguous piece of tallgrass prairie embedded in a landscape dominated by agriculture, though the predominant land use on the SNG is grazing by domestic livestock. Although amphibians often occur in a metapopulation typ~ structure where individual wetlands represent patches, continued fragmentation and isolation of habitat will cause populations to go extinct if colonization is not sufficient to offset local extinction. Because many factors may influence habitat use and occupancy of amphibian populations, best subsets logistic regression was used to develop occupancy and extinction models for these amphibian species using a whole suite of variables related to wetland hydroperiod, wetland isolation, patch quality, and landscape complementation

    Landscape genetics reveal broad and fine‐scale population structure due to landscape features and climate history in the northern leopard frog (Rana pipiens) in North Dakota

    Get PDF
    Prehistoric climate and landscape features play large roles structuring wildlife populations. The amphibians of the northern Great Plains of North America present an opportunity to investigate how these factors affect colonization, migration, and current population genetic structure. This study used 11 microsatellite loci to genotype 1,230 northern leopard frogs (Rana pipiens) from 41 wetlands (30 samples/wetland) across North Dakota. Genetic structure of the sampled frogs was evaluated using Bayesian and multivariate clustering methods. All analyses produced concordant results, identifying a major east–west split between two R. pipiens population clusters separated by the Missouri River. Substructuring within the two major identified population clusters was also found. Spatial principal component analysis (sPCA) and variance partitioning analysis identified distance, river basins, and the Missouri River as the most important landscape factors differentiating R. pipiens populations across the state. Bayesian reconstruction of coalescence times suggested the major east– west split occurred ~13–18 kya during a period of glacial retreat in the northern Great Plains and substructuring largely occurred ~5–11 kya during a period of extreme drought cycles. A range‐wide species distribution model (SDM) for R. pipiens was developed and applied to prehistoric climate conditions during the Last Glacial Maximum (21 kya) and the mid‐Holocene (6 kya) from the CCSM4 climate model to identify potential refugia. The SDM indicated potential refugia existed in South Dakota or further south in Nebraska. The ancestral populations of R. pipiens in North Dakota may have inhabited these refugia, but more sampling outside the state is needed to reconstruct the route of colonization. Using microsatellite genotype data, this study determined that colonization from glacial refugia, drought dynamics in the northern Great Plains, and major rivers acting as barriers to gene flow were the defining forces shaping the regional population structure of R. pipiens in North Dakota

    Influences of Cattle on Postmetamorphic Amphibians on the Cumberland Plateau

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    Global decline of amphibian populations has been linked to various anthropogenic stressors. Recent studies have quantified the influences of cropland agriculture and deforestation; however, few have examined the impacts of allowing cattle access in wetlands on resident amphibians. I compared four wetlands exposed to cattle grazing for \u3e10 years against four wetlands that had not been grazed for \u3e10 years, at the University of Tennessee Plateau Research and Education Center. At each wetland I measured species richness, diversity, and species-specific relative abundance of postmetamorphic amphibians captured in pitfall traps and during breeding call surveys, amphibian egg mass abundance, shoreline vegetation structure, and soil compaction from March – August 2005 and 2006. Pathogen prevalence and histopathological changes were measured from a subsample of opportunistically collected amphibians. Landscape characteristics were quantified and related to amphibian community structure. Relative abundance of green frog metamorphs was 9.8X greater in 2006 and 2.3X greater in 2005 at non-access wetlands. Relative abundance of American toads was 68X and 76X greater at cattle-access wetlands in 2005 and 2006, respectively. Breeding call abundance of American toad, Fowler’s toad, and Cope’s gray treefrog was 4 – 25X greater at cattleaccess wetlands in 2006. There were 2X more spring peepers and pickerel frogs calling at non-access wetlands in 2005 and 2006, respectively. Species richness, diversity, and egg mass abundance were not significantly different between land-use types each year. In general, body size followed a density-dependent relationship across species. Height and percent horizontal and vertical cover of shoreline vegetation were 74%, 25% and 84% greater, respectively, in non-access wetlands in 2005; trends were similar in 2006. Soil compaction was 55% greater at cattle-access wetlands. Pathogen prevalence and histopathological changes did not differ between land uses. Landscape analyses revealed species-specific associations related to wetland isolation and geometric complexity of the landscape between wetlands. My results suggest that cattle influence community composition and postmetamorphic body size of amphibians, but effects are speciesspecific. Differences in postmetamorphic abundance may be related to less vegetation structure and lower water quality at cattle-access wetlands. Fencing cattle from wetlands may be a prudent conservation strategy for some amphibian species

    Using photo identification to estimate the population size of nyala (tragelaphus angasii) in Umkhuzi Game Reserve

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    A research report submitted to the Faculty of Science, in partial fulfilment of the requirements for the degree of Master of Science in Environmental Science, University of the Witwatersrand, Johannesburg, 2015.Wildlife conservation and management requires an in-depth understanding of the demographics and dynamics of the population concerned to enable sound management decisions. Yet it is often very challenging to obtain reliable information of cryptic and highly migratory species. I used photo identification and capture-recapture methods to study the population of nyala, a highly secretive species, in the Umkhuzi game reserve. The nyala species is individually identifiable by the mark pattern on their body. Photographs used for this project were taken at a waterhole in Umkhuzi game reserve between June 23rd and 01 July 2014, representing nine sampling occasions. Identification of individuals was achieved with a computer-assisted technique using open source pattern identification software called Wild-ID version 1.0.1. A total of 652 photographs were taken at the sampling site and from these pictures wild-ID identified 372 distinct animals. An encounter history for each individual during the nine sampling occasions was also produced using Wild-ID. The encounter histories of all individuals were entered into Program MARK. I used the closed population models in Program MARK to obtain population estimates. Program MARK indicated that Mh was the most appropriate model to fit this data as indicated by the AICc ranking. Mh showed population estimates as follows: adult males: 111.90 ± 16.07, adult females: 298.01 ± 36.66; young adult males: 21.33 ±19.34; juvenile males: 37.15 ±16.84; yearling males: 37.73 ±8.51; yearling females: 96.48 ±22.75 and juvenile unidentified: 69.03. ±28.96 Closure test performed to ascertain demographic and geographic closure during the sampling period showed a χ2= 21.74, p= 0.08, df = 14, for the Stanley & Burnham test and a p and z-values of 0.06 and -1.51 respectively for the Otis et al test. These results shows marginal violation of population closure, nevertheless closed population models were used to estimate population abundance due to the fact the violations are marginal and the sampling period iii was very short, nine days. The study revealed that there is as much as twice the number of females compared to males

    Acoustic ecology of marine mammals in polar oceans

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    In polar habitats, research on marine mammals including studies of the possible ecological consequences of anthropogenic impact is hampered by adverse climate conditions restricting human access to these regions. Marine mammals are known to produce sound in various behavioural contexts, rendering (hydro-)acoustic recording techniques, which are quasi-omnidirectional and independent of light and weather conditions, an apt tool for year round monitoring of marine mammal presence and behaviour in polar habitats. Acoustic behaviour is shaped by the species-specific behavioural ecology, as well as by abiotic, biotic and anthropogenic factors of the animal's living environment, a concept known as acoustic ecology. Acoustic ecology thereby describes the interaction between an animal and its environment as mediated through sound. An understanding of the acoustic ecology is important when interpreting acoustic data, as the acoustic ecology of a species determines if physical presence results in acoustic presence, on which temporal scale acoustic activity occurs and over which spatial scales acoustic presence can be detected. This thesis comprises ten manuscripts/papers, which are based on acoustic data collected in the Southern and Arctic Oceans. All provide examples of how aspects of the acoustic ecology of the species shape acoustic behaviour. In addition, the majority of manuscripts/papers also illustrate how acoustic monitoring can provide information of physical presence of marine mammals in areas where prolonged visual observations are not possible. Acoustic ecology forms the overarching concept that braces these publications. Given the relatively sparse literature on this concept with respect to marine mammals, this synopsis includes a first detailed conceptual description of acoustic ecology for polar habitats. Particular emphasis thereby is given to the specific environmental conditions in polar habitats and the looming threats of climatic change and other anthropogenic influences

    Relative Fitness and Behavioral Compensation of Amphibians in a Managed Forest

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    Habitat loss and degradation are two of the most important factors leading to the imperilment of species worldwide including amphibians, but mechanisms underlying these changes are poorly understood. To understand the fitness potential of harvested forests, I conducted studies of a forest specialist, Rana sylvatica (Wood Frogs) and compared these results with those from identical studies with an open canopy specialist, R. pipiens (Northern Leopard Frogs) in response to an unharvested control and three forest harvesting treatments: clearcutting (with removal of all merchantable timber \u3e 10 cm diameter), clearcutting with coarse woody debris retention, and partial harvesting with removal of \u3c 25% canopy cover. First, I used radio-telemetry data collected on 72 adult R. sylvatica and 40 R. pipiens and logistic regression modeling to assess habitat selection Second, I predicted and quantified the plasticity of the two frogs with respect to survival, time to metamorphosis, and growth rate. My results suggest that R. pipiens may use clearcut areas during the spring and summer that are within migration distance of breeding and overwintering habitats if dense ground vegetation has regenerated. However, the fitness potential of the clearcut treatments for R. sylvatica is lower than that of the forested treatments, and coarse woody debris retention may ameliorate some of the effects of clearcut harvesting. Further, partial harvesting with removal of \u3c 25% canopy cover is a forest management technique that may not adversely influence the fitness of R. sylvatica. Larval R. sylvatica from open-canopy treatments reached a minimum size and metamorphosed earlier than other treatments, but ultimately, juveniles attained the same mass in all four treatments; open-canopy treatments, however, had 35 ± 2% fewer survivors than forested treatments. In contrast, survival of R. pipiens larvae increased with decreasing canopy cover, increasing water temperature, and increasing food availability, and juveniles remained larger and had higher survival in open-canopy treatments. In summary, the treatments induced opposing changes in the fitness correlates at the aquatic and terrestrial life stages of R. sylvatica but not R. pipiens. Further, each species selected different harvest treatments, and havesting affected the habitat selection of both species at multiple scales
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