A molecular phylogeny of Bopyroidea and Cryptoniscoidea (Crustacea: Isopoda)

Abstract

Epicaridean isopods are parasitic on other crustaceans. They represent a diverse group of highly derived taxa in two superfamilies and 10 families. Little work has been done on the phylogeny of these parasites because of the difficulty in defining homologous characters for adults above the genus level. The females exhibit morphological reduction of characters and the males have few distinguishing characters. Moreover, epicarideans have only rarely been included in past studies of isopod phylogeny. Our objective was to derive a phylogeny of epicaridean taxa based on 18S rDNA, then use that phylogeny to examine the relationships of the bopyrid subfamilies, bopyroid families and epicarideans to cymothoid isopods. We tested the monophyly of the Epicaridea, evaluated hypotheses on relationships among epicaridean families and subfamilies, examined the evolution of the abdominal mode of infestation on caridean, gebiidean, axiidean and anomuran hosts and examined coevolution between epicarideans and their crustacean hosts. The molecular phylogeny indicated that Epicaridea were monophyletic with respect to Cymothooidea. Bopyroidea formed a monophyletic group without Dajidae and Entophilinae (now as Entophilidae). Both latter taxa grouped with Cryptoniscoidea, and this group was the sister taxon to the redefined Bopyroidea in all trees. The bopyrid subfamily Ioninae is the sister taxon to the other bopyrid subfamilies (except Entophilidae). Ioninae was elevated to family status but found not to be monophyletic; a new subfamily, Keponinae, was erected for all genera formerly placed in Ioninae except the type genus. The abdominal mode of parasitism appears to have evolved independently among the subfamilies. Coevolution between host and parasite phylogenies showed extensive incongruence, indicating frequent host-switching as a general pattern in Epicaridea.http://www.zoobank.org/urn:lsid:zoobank.org:pub:30ECFB13-2795-494E-AABE-6B5F84A57A67