Toward a Better Understanding of the Phylogeny of the Asplanchnidae (Rotifera)

We investigated the phylogenetic relationships of Family Asplanchnidae using both morphological and molecular data. The morphological database, comprising 23 characters from 19 taxa (15 Asplanchnidae and 4 outgroups), was compiled from a survey of the literature and our own observations; the molecular data (ITS and V4 region nuclear regions and mitochondrial cox1) was sequenced from specimens that we collected. Our analysis of the morphological data set (maximum parsimony) yielded 12 most-parsimonious trees with a tree length of 27 steps. From this analysis we conclude (1) Asplanchnidae is a monophyletic group as are the three genera comprising it, (2) there is no compelling support for the argument that Asplanchna should be separated into two discrete genera, and (3) there is some support for the proposal that Asplanchnidae and Synchaetidae are sister groups. Our analysis of the molecular data set supports the first two of these conclusions while the sister group of the family varied depending on the gene region analyzed and families and genera included. Current understanding of the phylogeny of Asplanchnidae is hampered by the need for additional informative morphological characters and a lack of molecular data for the genus Harringia and several other members of the Asplanchnidae.