A comparative analysis of genetic differentiation of the E. affinis species complex and some other Eurytemora species, using the CO1, nITS and 18SrRNA genes (Copepoda, Calanoida)

Abstract

Abstract Eurytemora represents a challenging group of species due to their taxonomy, in particular the former group of cryptic species known as E. affinis sensu lato. In this paper, we analyse DNA sequences that are all available in GenBank, along with our own data on the genus Eurytemora. For this study, a set of mitochondrial and nuclear genes (CO1, nITS and 18SrRNA) was used. In total 543 sequences were analysed (437 CO1; 54 nITS; 52 18SrRNA). However, this work is mainly meta-analytical, and only 67 sequences from unstudied earlier populations or species were obtained specifically for this work to analyse the genetic differentiation of the morphologically described species. We found that relatively young species of the E. affinis complex are different from each other in the CO1 and nITS genes, but not in the conservative 18SrRNA nuclear gene. Nucleotide differences among affinis-group species in the CO1 gene are 9.4-11.8%; in the nITS genes, 1.1-5.0%. At the same time, all other studied Eurytemora species have significant differences from each other in the CO1 and nITS genes, as well as in 18SrRNA. The level of differences among the species is 13.2-19.2% for the CO1 gene, 18.0-27.6.2% for nITS genes, and 0.4-1.8% for the 18SrRNA gene.