Ecological and evolutionary determinants of microbial community composition on the amphibian skin

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Amphibians are a vertebrate group with a high proportion of species threatened with extinction, to a great part due to emerging pathogens. They are also well-known for the variety of toxins in their skin which are assumed to have evolved as a antimicrobial defense but which might also undergo microbe-mediated biotransformation. Knowledge on the microbial communities associated with the amphibian skin is surprisingly scarce despite their importance to understand ecology and evolution and improve conservation of amphibians. The proposed project aims at understanding the patterns of microbial communities in the amphibian skin, their assembly process, and their influence on toxin production. It will combine (i) screening of prokaryotic community composition using 454 and Illumina sequencing of samples from German and Madagascan amphibians, (ii) testing for host-phylogeny vs. habitat influences on these communities, (iii) assess positive and negative species associations among microbes, (iv) monitor microbe community dynamics on the same amphibian specimen over time, and community assembly after antibiotic treatment, and (v) screen amphibian macroglands for presence of symbiontic bacteria and screen changes in toxin production before and after antibiotic treatment. Data will be analysed to test various hypotheses such as a lower diversity of prokaryotic communities on the amphibian skin compared to other skin habitats due to the large amount of antimicrobial substances, the origin of these communities from the environment rather than vertical transmission, and the involvement of skin microbes in production and biotransformation of amphibian toxins.