DAO prepress abstract  -  DOI: https://doi.org/10.3354/dao03379

Did we miss something? Acanthocephalan infection patterns in amphipods: a reappraisal in the light of recently discovered host cryptic diversity

Matthias Galipaud, Loïc Bollache, Clément Lagrue*

*Email: lagrue@ualberta.ca

ABSTRACT: Amphipods are model species in studies of pervasive biological patterns such as sexual selection, size assortative pairing and parasite infection patterns. Cryptic diversity (i.e. morphologically identical but genetically divergent lineages) has recently been detected in several species. Potential effects of such hidden diversity on biological patterns remain unclear but potentially significant. It begs the question, have we missed part of the picture by involuntarily overlooking the occurrence and effects of cryptic diversity on biological patterns documented by previous studies? We test for potential effects of cryptic diversity on parasite infection patterns in amphipod populations and discuss the implications of our results in studies in the context of previously documented host-parasite infection patterns, especially amphipod-acanthocephalan associations. We assessed infection levels (prevalence and abundance) of three acanthocephalan species, Pomphorhynchus laevis, Pomphorhynchus tereticollis and Polymorphus minutus, among cryptic lineages of the Gammarus pulex/Gammarus fossarum species complex and Gammarus roeselii from sampling sites where they occur in sympatry. We also evaluated potential differences in parasite-induced mortality among host molecular operational taxonomic units (i.e. MOTU)–parasite species combinations. Acanthocephalan prevalence, abundance and parasite-induced mortality varied widely among cryptic MOTUs and parasite species; infection patterns were more variable among MOTUs than sampling sites. Overall, cryptic diversity in amphipods strongly influenced apparent infection levels and parasite-induced mortality. Future research on species with cryptic diversity should account for potential effects on documented biological patterns. Results from previous studies may also need to be reassessed in the light of cryptic diversity and its pervasive effects.