I am working on host-parasite interactions. More specifically, I focus on the trematode parasite Atriophallophorus winterbourni and its host, the freshwater snail Potamopyrgus antipodarum. Although P. antipodarum is an invasive species that has colonised freshwater habit on several continents, I study the snail and its parasite in their native range in New Zealand. The study system is of great interest since natural populations of the snail in New Zealand often consist of a mixture of clonally reproducing females and sexually reproducing males and females.
Some of my research highlights at Eawag:
- During its life cycle, the parasite has to pass through two hosts: the snail is its intermediate host and waterfowl are definitive hosts. I have found evidence that the parasite A. winterbourni is likely to induce migration of its snail host to shallow water habitat. This trait may facilitate trophic transmission to dabbling ducks.
- Phylogeographic patterns in New Zealand are often found to have been influenced by Pleistocene glaciation and/or the formation of the Southern Alps. This holds for many diverse organisms, including birds, insects and plants. Through molecular characterisation of A. winterbourni parasites from lakes around New Zealand's South Island, evidence was found supporting the idea that genetic differentiation between populations of this trematode also bear the signature of Pleistocene Climate change and mountain formation.
- Organisms that look very similar to the human eye may be wrongly assigned to a single species. This turned out to be true for the parasite A. winterbourni as well. Molecular data support the existence of at least three species that co-exist in the same lakes and that all infect P. antipodarum snails. Interestingly, these parasite species may be ecologically divergent. Shallow-water snails are more frequently infected by A. winterbourni, while deep-water snails are more frequently infected by another Atriophallophorus species. A possible explanation for this ecological divergence could be that the latter species does not have the behavioural manipulation trait (see the first highlight) and that its definitive hosts are diving ducks, rather than dabbling ducks. More research will be required to understand this pattern and the drivers of speciation amongst these trematodes.