Map of locations of study sites within Missouri, USA.

<p>Map of locations of study sites within Missouri, USA.</p

SIMPER analysis of macroinvertebrate communities in Bd and non-Bd ponds.

<p>Over 50% of the difference in macroinvertebrate communities between Bd and non-Bd ponds was explained by the abundances of 10 of the 68 total invertebrate taxa (listed in order of decreasing relative contribution).</p

Why Does Amphibian Chytrid (<i>Batrachochytrium dendrobatidis</i>) Not Occur Everywhere? An Exploratory Study in Missouri Ponds

<div><p>The amphibian chytrid fungus, <i>Batrachochytrium dendrobatidis</i> (Bd), is a globally emerging pathogen that has caused widespread amphibian population declines, extirpations, and extinctions. However, Bd does not occur in all apparently suitable amphibian populations, even within regions where it is widespread, and it is often unclear why Bd occurs in some habitats but not others. In this study, we rigorously surveyed the amphibian and invertebrate biodiversity of 29 ponds in Missouri, screened resident amphibian larvae (<i>Rana (Lithobates</i>) sp.) for Bd infection, and characterized the aquatic physiochemical environment of each pond (temperature pH, conductivity, nitrogen, phosphorus, and chlorophyll-a). Our goal was to generate hypotheses toward answering the question, “Why does Bd not occur in all apparently suitable habitats?” Bd occurred in assayed amphibians in 11 of the 29 ponds in our study area (38% of ponds). We found no significant relationship between any single biotic or abiotic variable and presence of Bd. However, multivariate analyses (nonmetric multidimensional scaling and permutational tests of dispersion) revealed that ponds in which Bd occurred were a restricted subset of all ponds in terms of amphibian community structure, macroinvertebrate community structure, and pond physiochemistry. In other words, Bd ponds from 6 different conservation areas were more similar to each other than would be expected based on chance. The results of a structural equation model suggest that patterns in the occurrence of Bd among ponds are primarily attributable to variation in macroinvertebrate community structure. When combined with recent results showing that Bd can infect invertebrates as well as amphibians, we suggest that additional research should focus on the role played by non-amphibian biota in determining the presence, prevalence, and pathogenicity of Bd in amphibian populations.</p></div

NMDS plots of Bd and non-Bd ponds according to their resident species.

<p>Ponds are ordinated according to Raup-Crick incidence-based indices (top row; A, B, and C) and Bray-Curtis abundance-based indices (bottom row; D, E, and F) of resident amphibian (left column; A and D), macroinvertebrate (center column; B and E), and zooplankton (right column; C and F) species. Bd ponds are light gray diamonds (encircled by the white 95% confidence ellipse) and non-Bd ponds are black circles (encircled by the dark 95% confidence ellipse). Ponds that are closer together are more similar to each other. In incidence-based ordinations (A, B, and C), dispersion distance is analogous to beta diversity. Dispersion difference is significantly lower (*) for groups of Bd ponds in A, B, and E.</p

Structural equation modeling of factors correlating with Bd incidence.

<p>Structural equation modeling reveals that the correlation between physiochemical dissimilarity and Bd incidence is an indirect effect, mediated by macroinvertebrate community dissimilarity; macroinvertebrate community dissimilarity shares the only significant direct correlation with Bd incidence. Direct links are represented as solid lines and indirect links are represented as dashed lines. Significance of each correlation is reported as a p value, and significant links are emphasized in bold. Only significant links from the saturated model (A) were used to build the final, nested model (B). Standardized effect sizes for each link and a test of model fit are included (in italics) for the final model.</p

NMDS plot of Bd and non-Bd ponds according to pond physiochemistry.

<p>Ponds are ordinated according to Euclidian dissimilarities of standardized physiochemical variables (conductivity, pH, total nitrogen, total phosphorus, and chlorophyll-a). Bd ponds are light gray diamonds (encircled by the white 95% confidence ellipse) and non-Bd ponds are black circles (encircled by the dark 95% confidence ellipse). Ponds that are closer together are more similar to each other. Dispersion distance is significantly lower for the group of Bd ponds.</p

Supplement 1. R script for calculating the Raup-Crick metric as described in the text.

<h2>File List</h2><blockquote> <p><a href="Raup-Crick.txt">Raup-Crick.txt</a> -- (MD5: c37b2472e568eae3f1c0a5f1adec3d80)</p> </blockquote><h2>Description</h2><blockquote> <p>The code included in Raup-Crick.txt allows one to perform the null model analyses described in the text. The resulting values represent the degree to which observed numbers of shared species between any two sites differ from what would have been expected by random chance given the number of species co-occurring in each of two localities, and the designated regional species pool.</p> </blockquote

Dead Shrimp Blues: A Global Assessment of Extinction Risk in Freshwater Shrimps (Crustacea: Decapoda: Caridea)

<div><p>We present the first global assessment of extinction risk for a major group of freshwater invertebrates, caridean shrimps. The risk of extinction for all 763 species was assessed using the IUCN Red List criteria that include geographic ranges, habitats, ecology and past and present threats. The Indo-Malayan region holds over half of global species diversity, with a peak in Indo-China and southern China. Shrimps primarily inhabit flowing water; however, a significant subterranean component is present, which is more threatened than the surface fauna. Two species are extinct with a further 10 possibly extinct, and almost one third of species are either threatened or Near Threatened (NT). Threats to freshwater shrimps include agricultural and urban pollution impact over two-thirds of threatened and NT species. Invasive species and climate change have the greatest overall impact of all threats (based on combined timing, scope and severity of threats).</p></div

Extinction risk in the various shrimp families, expressed as a percentage of species richness per family.

<p>Extinction risk in the various shrimp families, expressed as a percentage of species richness per family.</p

Global extinction risk of freshwater shrimps.

<p>Global extinction risk of freshwater shrimps.</p