Ambystoma talpoideum (Mole Salamander). Oviposition mode and timing
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Herpetological Review↗
Geology topics
S.C. Walls
Publications and source records attributed to S.C. Walls.
Widespread occurrence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in the southeastern USA
From 1999 to 2006, we sampled >1200 amphibians for the fungal pathogen Batrachochytnum dendrobatidis (Bd) at 30 sites in the southeastern USA. Using histological techniques or PCR assays, we detected chytrid infection in 10 species of aquatic-breeding amphibians in 6 states. The prevalence of chytrid infection was 17.8% for samples of postmetamorphic amphibians examined using skin swab-PCR assays (n = 202 samples from 12 species at 4 sites). In this subset of samples, anurans had a much higher prevalence of infection than caudates (39.2% vs. 5.5%, respectively). Mean prevalence in ranid frogs was 40.7 %. The only infected salamanders were Notophthalmus viridescens at 3 sites. We found infected amphibians from late winter through late spring and in 1 autumn sample. Although we encountered moribund or dead amphibians at 9 sites, most mortality events were not attributed to Bd. Chytridiomycosis was established as the probable cause of illness or death in fewer than 10 individuals. Our observations suggest a pattern of widespread and subclinical infections. However, because most of the sites in our study were visited only once, we cannot dismiss the possibility that chytridiomycosis is adversely affecting some populations. Furthermore, although there is no evidence of chytrid-associated declines in our region, the presence of this pathogen is cause for concern given global climate change and other stressors. Although presence-absence surveys may still be needed for some taxa, such as bufonids, we recommend that future researchers focus on potential population-level effects at sites where Bd is now known to occur. ?? Inter-Research 2008.
Southeast↗
The effect of community composition on persistence of prey with their predators in an assemblage of pond-breeding amphibians
We examined whether the species composition of a community influences the persistence of larval Ambystoma maculatum in assemblages composed of two larger intraguild predators (A. opacum and A. jeffersonianum) and an alternative prey species (tadpoles of Rana sylvatica). We predicted a priori that A. maculatum would have higher survival in more diverse communities containing alternative species of prey and top predators (A. opacum), the latter of which may lower the abundance of intermediate predators (A. jeffersonianum) via intraguild predation. In a factorial experiment, we manipulated the presence of larval A. opacum, A. jeffersonianum, and R. sylvatica in replicated artificial ponds containing larval A. maculatum. The presence of all three species significantly depressed biomass production in A. maculatum: biomass was highest in ponds lacking the other species and was zero in ponds initially containing all four species. Tadpoles severely reduced the growth of filamentous algae in the ponds. This, in turn, may have affected the abundance of some herbivorous prey of larval salamanders, although this possibility was not tested. The presence of congeneric predators severely restricted the presence in the water column of larval A. maculatum, which otherwise exhibited significant diel patterns of activity in the absence of predators. Together, the presence of tadpoles and a predator-mediated reduction in activity patterns may have limited foraging opportunities for A. maculatum, thus exacerbating the direct impact of predation on survival in this species. These results suggest that diverse assemblages consisting of these particular species may actually inhibit, rather than promote, inclusion of A. maculatum in some communities of pond-breeding amphibians.
Oecologia↗