Phylogenetic analysis of Macrobiotidae (Eutardigrada, Parachela): a combined morphological and molecular approach

Combined analyses of morphological and molecular data were used to resolve phylogenetic relationships within Macrobiotidae (Eutardigrada). Morphological data were analysed using a cladistic approach with a matrix comprising 15 taxa with 17 characters to obtain a phylogenetic reconstruction. Molecular data were obtained by sequencing the cytochrome c oxidase subunit I gene in seven species of Macrobiotidae and one of Eohypsibiidae (used as outgroup). The morphological character defining the family, symmetrical claw on each leg, turns out to be plesiomorphic. Moreover, neither morphological nor molecular analyses supports a monophyletic clade for the subfamily Macrobiotinae, whereas both support a well defined evolutionary line (Murrayinae) within the family. We propose elevating the latter to family level (Murrayidae) while temporarily retaining as valid the family Macrobiotidae (amending its diagnosis, including within it only Macrobiotinae). Murrayidae opens an interesting evolutionary prospective, because the entire line has differentiated without sexual reproduction, constituting an example of evolution of asexual lineages.