Co‐evolutionary patterns in congeneric monogeneans: a review ofDactylogyrusspecies and their cyprinid hosts

Abstract

Patterns associated with the evolution of parasite diversity, speciation and diversification were analysed usingDactylogyrusspecies (gill monogeneans) and their cyprinid hosts as a model. The aim of this study was to use this highly specific host–parasite systems to review: (1) the diversity and distribution ofDactylogyrusspecies, (2) the patterns of organization and structure ofDactylogyruscommunities, (3) the evolution and determinants of host specificity and (4) the mode ofDactylogyrusspeciation and co‐evolutionary patterns in thisDactylogyrus–cyprinid systems.Dactylogyrusare a highly diverse group of parasites, with their biogeography and distribution clearly linked to the evolutionary history of their cyprinid hosts. The coexistence of severalDactylogyrusspecies on one host is facilitated by increasing niche distances and the differing morphology of their reproductive organs. The positive interspecific and intraspecific interactions seem to be the most important factors determining the structure ofDactylogyruscommunities. Host specificity is partially constrained by parasite phylogeny. Being a strict specialist is an ancestral character forDactylogyrus, being the intermediate specialists or generalists are the derived characters. The evolution of attachment organ morphology is associated with both parasite phylogeny and host specificity. Considering larger and long‐lived hosts or hosts with several ecological characters as the measures of resource predictability, specialists with larger anchors occurred on larger or longer‐living fish species. Intra‐host speciation, a mode of speciation not often recorded in parasites, was observed inDactylogyrusinfecting sympatric cyprinids. Sister parasite species coexisting on the same host occupied niches that differed in at least one niche variable. Intra‐host speciation, however, was not observed inDactylogyrusspecies of congeneric hosts from geographically isolated areas, which suggested association by descent and host‐switching events.