Development of representative species-level molecular markers and morphological character analysis of leucothoid amphipods (Crustacea: Amphipoda)
Leucothoid amphipods were investigated using morphology and molecular rDNA gene sequence fragments. The morphological diagnostic characters for traditional taxonomy have been clarified, a molecular marker for representative species has been developed, and one of the current anamorph-leucomorph connections has been confirmed with molecular sequence data. Ultimately this study has combined traditional morphological and modern molecular methods to clarify the taxonomy and to propose a preliminary phylogeny of the Leucothoidae. Analysis of 18S rDNA gene fragments from 13 species in two genera supported the current morphological species designations and the separation of the family into two clades. Combined analysis of 18S rDNA and COI mtDNA gene fragments revealed cryptic speciation in one species occurring in Belize and Florida. For the first time in a single work, diagnostic descriptions were presented for all extant species of the Leucothoidae. Fourteen new species of Leucothoe and one new species of Paranamixis were described from Lizard Island, Australia. Morphological cladistic analysis of 64 species of the "leucothoid clade" and 33 species of the "anamixid clade" supported the collapse of the genus Leucothoella and the classification of the genera Anamixis and Paranamixis as a single genus. The poor resolution of trees in these cladistic analyses suggests that rapid ancient speciation is likely a driving factor in the evolution of this family.