Host niche may determine disease-driven extinction risk

<div><p>The fungal pathogen <i>Batrachochytrium dendrobatidis</i> (<i>Bd</i>) drives declines and extinctions in amphibian communities. However, not all regions and species are equally affected. Here, we show that association with amphibian aquatic habitat types (bromeliad phytotelmata versus stream) across Central America results in the odds of being threatened by <i>Bd</i> being five times higher in stream microhabitats. This differential threat of <i>Bd</i> was supported in our study by a significantly lower prevalence of <i>Bd</i> in bromeliad-associated amphibian species compared to riparian species in Honduran cloud forests. Evidence that the bromeliad environment is less favorable for <i>Bd</i> transmission is exemplified by significantly less suitable physicochemical conditions and higher abundance of <i>Bd</i>-ingesting micro-eukaryotes present in bromeliad water. These factors may inhibit aquatic <i>Bd</i> zoospore survival and the development of an environmental reservoir of the pathogen. Bromeliad phytotelmata thus may act as environmental refuges from <i>Bd</i>, which contribute to protecting associated amphibian communities against chytridiomycosis-driven amphibian declines that threaten the nearby riparian communities.</p></div

Persistence of <i>B</i>. <i>dendrobatidis</i> in tank bromeliads versus stream water.

<p>For both aquatic microhabitats (bromeliad and stream) the boxplots represent (A) persistence of <i>B</i>. <i>dendrobatidis</i> in unfiltered water expressed as logarithmic value of genomic equivalents of viable <i>B</i>. <i>dendrobatidis</i> zoospores, (B) persistence of <i>B</i>. <i>dendrobatidis</i> in filtered water expressed as logarithmic value of genomic equivalents of viable <i>B</i>. <i>dendrobatidis</i> zoospores.</p

Boxplots showing micro-eukaryote diversity and abundance estimates using microscopy.

<p>For both aquatic microhabitats (bromeliad and stream) the boxplots represent (A) micro-eukaryote abundance expressed as micro-eukaryote count per ml (Bromeliad n = 31, Stream n = 24), (B) micro-eukaryote diversity expressed as number of different taxa per ml (Bromeliad n = 31, Stream n = 24).</p

Prevalence of <i>B</i>. <i>dendrobatidis</i> in the sampled amphibians.

<p>Prevalence data of <i>B</i>. <i>dendrobatidis</i> in the sampled amphibians divided in amphibian taxa, life stages and species.</p

Boxplot showing infection intensity of <i>B</i>. <i>dendrobatidis</i> in the sampled amphibians.

<p>Median (bars), interquartile range (boxes) and total range (whiskers) are shown (Bromeliad n = 116, Stream n = 150).</p