Phylogenetic relationships among Unionicola (Acari: Unionicolidae) mussel-mites of North America based on mitochondrial cytochrome oxidase I sequences

Abstract

Water mites of the genus Unionicola Haldeman, 1842 are common symbionts of molluscs, living on the gills or mantle and foot of their hosts and using these tissues as sites of oviposition. Phylogenetic relationships among species that comprise the genus are poorly understood and what is known has been based on a limited number of morphological and life history characters or molecular sequence data using closely-related taxa. The present study uses sequence data from the cytochrome oxidase subunit I (cox1) gene (664 bp) to reconstruct evolutionary relationships among representative species of North American Unionicola from eight subgenera that occur in symbiotic association with freshwater mussels. Maximum parsimony and maximum likelihood analysis yielded trees with similar topologies, and most of the branches have moderate to high bootstrap support. The topologies of these gene trees are mostly congruent with a previously published morphologically-derived tree. Specifically, the gene trees support monophyly among mites from subgenera that occur in association with the gill tissues of host mussels. The molecular trees of Unionicola mites generated by this study must, however, be interpreted with caution, given that the analysis is based exclusively on Unionicola subgenera from North America. A more robust phylogeny of Unionicola mussel-mites will require the addition of molecular sequence data from taxa outside of North America.