Urspelerpes, U. brucei

Number of Pages: 3Integrative BiologyGeological Science

Projected Loss of a Salamander Diversity Hotspot as a Consequence of Projected Global Climate Change

Background: Significant shifts in climate are considered a threat to plants and animals with significant physiological limitations and limited dispersal abilities. The southern Appalachian Mountains are a global hotspot for plethodontid salamander diversity. Plethodontids are lungless ectotherms, so their ecology is strongly governed by temperature and precipitation. Many plethodontid species in southern Appalachia exist in high elevation habitats that may be at or near their thermal maxima, and may also have limited dispersal abilities across warmer valley bottoms. Methodology/Principal Findings: We used a maximum-entropy approach (program Maxent) to model the suitable climatic habitat of 41 plethodontid salamander species inhabiting the Appalachian Highlands region (33 individual species and eight species included within two species complexes). We evaluated the relative change in suitable climatic habitat for these species in the Appalachian Highlands from the current climate to the years 2020, 2050, and 2080, using both the HADCM3 and the CGCM3 models, each under low and high CO 2 scenarios, and using two-model thresholds levels (relative suitability thresholds for determining suitable/unsuitable range), for a total of 8 scenarios per species. Conclusion/Significance: While models differed slightly, every scenario projected significant declines in suitable habitat within the Appalachian Highlands as early as 2020. Species with more southern ranges and with smaller ranges had larger projected habitat loss. Despite significant differences in projected precipitation changes to the region, projections did no

Detritus Quality and Locality Determines Survival and Mass, but Not Export, of Wood Frogs at Metamorphosis

Single-site experiments have demonstrated detritus quality in wetlands can have strongly negative, neutral, and even positive influences on wildlife. However, an examination of the influence of detritus quality across several regions is lacking and can provide information on whether impacts from variation in detritus quality are consistent across species with wide ranges. To address this gap in regional studies we examined effects of emergent and allochthonous detritus of different nutrient qualities on amphibians and assessed a mechanism that may contribute to potential impacts. We used aquatic mesocosms to raise wood frogs (Rana sylvatica) from two regions of the United States with whole plants from purple loosestrife (Lythrum salicaria), leaf litter from native hardwood trees, and a mixture of both. We examined several metrics of amphibian fitness and life history, including survival, number of days to metamorphosis, and size at metamorphosis. Further, we quantified whether the effects of detritus type could translate to variation in anuran biomass or standing stock of nitrogen or phosphorus export. Our results show detritus with high nutrient quality (purple loosestrife) negatively influenced survival of wood frogs, but increased size of metamorphic individuals in two different regions of the United States. Despite the decrease in survival, the increase in size of post-metamorphic anurans raised with high quality detritus resulted in anuran biomass and standing stock of N and P export being similar across treatments at both locations. These results further demonstrate the role of plant quality in shaping wetland ecosystem dynamics, and represent the first demonstration that effects are consistent within species across ecoregional boundaries

Stable isotopes reveal an invasive plant contributes more than native sources to anuran larvae diets

Foraging theory suggests organisms increase their fitness through dietary and energetic choices. In nature, organisms choose to consume balanced optimal diets but as exotic plants invade ecosystems, new foraging options become available. Often these plants have different traits and can negatively affect fitness of foragers by lowering survival or growth due to toxicity. Wetland habitats are highly susceptible to plant invasions which can have negative effects on nutrient cycling. The purpose of this study was to examine whether invasion of purple loosestrife (Lythrum salicaria) alters tadpole foraging preference thus potentially impacting their survivorship and fitness. We designed a common garden experiment and utilized stable isotopic signatures to investigate the contribution of purple loosestrife and native hardwood detritus to larval wood frog (Rana sylvatica) and southern leopard frog (Rana sphenocephala) diets. Tadpoles derived a higher percentage of resources from purple loosestrife compared to native hardwood detritus when presented with both options, despite its high concentration of toxic secondary compounds. It is unknown if tadpoles can detect competing fitness signals that may be associated with higher nutrient and toxicity levels in purple loosestrife. Discovering the presence or absence of such signals will promote a greater understanding of selective foraging in changing environments

Detritus Quality Produces Species-Specific Tadpole Growth and Survivorship Responses in Experimental Wetlands

Although many non-native species negatively influence amphibian populations, non-native aquatic vegetation has been documented to have positive, negative, and neutral effects on anuran larvae. To evaluate the response of anurans to non-native plants, we exposed two frog species, Gray Treefrog (Hyla versicolor-chrysoscelis) and Southern Leopard Frog (Lithobates sphenocephalus), to detritus from either native hardwood trees, non-native purple loosestrife (Lythrum salicaria), or a mixture of both. Experiments were conducted in artificial ponds, and we recorded the survival, growth, and metamorphic size of larvae. Gray Treefrog survival was highest in tanks with native leaf litter. Developmental time did not differ among treatments, but tadpoles in tanks with purple loosestrife were significantly larger than those in tanks with native leaf litter. Southern Leopard Frog survival was lowest in the mixed vegetation treatment. As with Gray Treefrogs, developmental time was not influenced by treatment, but larvae from tanks with purple loosestrife were significantly larger than those from other treatments. Lower survival in the presence of purple loosestrife has been linked to secondary compounds in the plant, and the higher growth rates we observed are consistent with recent findings on response of anuran larvae to other non-native plants. Our results suggest the negative effects of purple loosestrife detritus on the species examined are manifest at the individual and (perhaps) population level. Because the fewer animals that did survive in tanks with purple loosestrife grew larger, overall ecosystem-level effects may not be present; however, larger scale experiments are needed to evaluate this hypothesis

Standing stock of anurans.

<p>(a–b) Standing stock of N and P and (c) biomass of metamorphic wood frogs raised in the presence of all treatments at Clemson (CLEM) and Lindenwood (LIN). Error bars represent ±1 SD. Biomass and standing crop of N and P was significantly different across sites.</p

Anuran fitness.

<p>(a) Number of days of development, (b) number of surviving individuals, and (c) wet mass (g) for wood frogs at Clemson (CLEM) and Lindenwood (LIN) raised in the presence of low, high or mixed treatments. Sample sizes of individuals measured above each bar. Different upper case letters represent significant differences between treatments within a site. Error bars represents ±1 SD.</p

Standing crop statistics.

<p>Standing crop statistics.</p

Response to detritus quality.

<p>Response to detritus quality.</p

Stoichiometry statistics.

<p>Stoichiometry statistics.</p