Identification and Phylogeny of Cryptic Species of the Daphnia Longispina Complex (Anomopoda, Daphniidae) Using ITS2 Secondary Structure

Abstract

Cladocerans of the genus Daphnia O.F. Müller (Crustacea: Cladocera) are typical members of different types of water bodies and are used as model organisms in various biological disciplines. Within the genus, a considerable number of closely related and cryptic species are noted, the identification of which by morphological traits often causes difficulties. In the present study, species identification in the Daphnia longispina complex, namely, D. longispina O.F. Müller, D. hyalina Leydig, D. umbra Taylor, Hebert et Colbourne, and D. cf. longispina, was performed using data on the predicted secondary structure of the second internal transcribed spacer (ITS2) of the nuclear rDNA. Phylogenetic analysis carried out using the Profile Neighbor-Joining algorithm and the analysis of compensatory base changes supported the species status of D. hyalina and D. cf. longispina. It was demonstrated that the data on the ITS2 secondary structure can be used to resolve complex taxonomic problems in the study of cladocerans in general and the species complexes in particular.