engleski

Multilocus phylogenetic analyses reveal that habitat selection drives the speciation of Didymozoidae (Digenea) parasitizing Pacific and Atlantic bluefin tuna

Parasite communities of wild and reared bluefin tuna display remarkable diversity. Among these, the most prevalent and abundant are the Didymozoidae (Monticelli, 1888) (Trematoda, Digenea), considered one of the most taxonomically complex digenean families. The aim of this study was to evaluate phylogenetic structure of Didymozoidae occurring in Pacific (Thunnus orientalis) and Atlantic bluefin tuna (T. thynnus) in order to increase our knowledge of didymozoid zoogeography, and to identify species that could be successfully employed as biological tags for stock assessment studies. For our analyses we used two ribosomal DNA loci (28S, second Internal Transcribed Spacer - ITS-2) and a mitochondrial gene (cytochrome oxidase 1 - CO1). In most parasitic groups, morphology is the primary factor in the structuring of phylogenetic relationships. In rare examples, however, habitat has been suggested as a primary factor affecting parasite evolution. During their evolution, didymozoids have spread and inhabited a remarkable number of different sites in their hosts, colonizing exterior as well as strictly interior niches. Our data suggest that habitat selection has been the leading force in shaping didymozoid phylogenetic relationships. For two didymozoid species (D. wedli and D. palati), CO1 sequences indicate intraspecific differences between Mexican and Adriatic populations.

Didymozoidae; phylogeny; Thunnus orientalis; T. thynnus

nije evidentirano