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Evolutionary relationships between trematodes and snails emphasizing schistosomes and paragonimids.
1School of Tropical Biology, James Cook University, Townsville, Qld, Australia. david.blair@jcu.edu.au
Parasitology
|January 5, 2002
Summary
Digenean parasites, like schistosomes and Paragonimus lung flukes, exhibit diverse host-switching strategies with their snail hosts. Phylogenetic tracking, not just an arms race, explains how these parasites adapt to new snail species across evolutionary time.
Area of Science:
- Parasitology
- Evolutionary Biology
- Molecular Phylogenetics
Background:
- Snails and digenean flatworms share a 200-million-year evolutionary history, marked by complex interrelationships.
- Understanding host specificity and distribution requires examining host-parasite phylogenies.
Purpose of the Study:
- To investigate evolutionary relationships between digenean parasites (Schistosomatidae, Paragonimidae) and their gastropod hosts.
- To explain current host specificity and distributions using phylogenetic data.
- To evaluate coevolution theories in light of new findings.
Main Methods:
- Comparative phylogenetic analysis of digenean families (Schistosomatidae, Paragonimidae) and their gastropod hosts.
- Examination of host-parasite associations across different phylogenetic depths.
- Review of existing knowledge on snail-digenean coevolutionary dynamics.
Main Results:
- Both Schistosomatidae and Paragonimidae utilize diverse snail families, indicating host extensions.
- Schistosomatids associate with a wider phylogenetic range of snails than paragonimids.
- Modern schistosomes are more host-specific than paragonimids, with fewer host family additions.
Conclusions:
- Phylogenetic tracking, rather than solely an "arms race," may explain digenean host-switching capabilities.
- Digeneans can switch to new snail hosts, including ecologically equivalent but unrelated species.
- Coevolutionary dynamics are complex, allowing switches across significant phylogenetic distances.