Vicariance in a generalist fish parasite driven by climate and salinity tolerance of hosts

Abstract

AbstractAcanthocephalans are parasites with complex lifecycles that are important components of aquatic systems and are often model species for parasite-mediated host manipulation. Genetic characterization has recently resurrectedPomphorhynchus tereticollisas a distinct species fromPomphorhynchus laevis, with potential implications for fisheries management and host manipulation research. Morphological and molecular examinations of parasites from 7 English rivers across 9 fish species revealed thatP. tereticolliswas the onlyPomphorhynchusparasite present in Britain, rather thanP. laevisas previously recorded. Molecular analyses included two non-overlapping regions of the mitochondrial gene – cytochrome oxidase and generated 62 sequences for the shorter fragment (295 bp) and 74 for the larger fragment (583 bp). These were combined with 61 and 13 sequences respectively, from Genbank. A phylogenetic analysis using the two genetic regions and all the DNA sequences available forP. tereticollisidentified two distinct genetic lineages in Britain. One lineage, possibly associated with cold water tolerant fish, potentially spread to the northern parts of Britain from the Baltic regionviaa northern route across the estuarine area of what is now the North Sea during the last Glaciation. The other lineage, associated with temperate freshwater fish, may have arrived laterviathe Rhine/Thames fluvial connection during the last glaciation or early Holocene when sea levels were low. These results raise important questions on this generalist parasite and its variously environmentally adapted hosts, and especially in relation to the consequences for parasite vicariance.