Discussion

Biodiversity loss caused by human activities threatens the capacity of ecosystems worldwide to provide essential ecological services. Hence, a growing effort is directed at understanding the consequences of anthropogenic disturbances for biodiversity. Parasitic organisms have so far been widely overlooked in this effort, even though parasitism is the most common feeding strategy on Earth. One group of parasites with high societal relevance are the trematodes, flatworms utilizing snails as intermediate hosts to infect vertebrate species, including humans, as final host. Trematodes cause important human diseases such as schistosomiasis, a neglected tropical disease affecting more than 200 million people. Here we aim to document the patterns and processes governing the local and regional diversity of trematodes infecting the hosts of schistosomiasis - Bulinus and Biomphalaria snails - in a crater-lake district in western Uganda which bridges the temperature threshold of schistosomiasis presence. As these lakes cover a wide gradient of human-impact intensity, this crater-lake system represents a natural laboratory to analyze the impact of both natural and anthropogenic environmental variation on trematode diversity within and among lakes. In order to tackle existing difficulties in detecting and identifying trematode infections in snails, we are developing a multiplexing and pooling techniques by means of next-generation-sequencing. This genotyping by targeted sequencing allows to simultaneously amplify loci for host and parasite, which will increase the genomic coverage and thus the power to infer population dynamic processes, population genetic structure, genetic diversity and phylogeography.