Application of Modern Approaches to Species Delimitation in Freshwater Erpobdellidae (Hirudinea: Arhynchobdellida) with a New Interpretation of Their Genera

Abstract

The traditional taxonomy of freshwater invertebrates is a labor-intensive process requiring extensive knowledge and experience. In addition, this science is largely subjective, which makes its digitalization difficult. However, accurate species attribution is becoming increasingly important for environmental surveys and conservation efforts. In the 21st century, molecular biology methods have proven to be a successful tool for objectively determining biodiversity. Achieving objectivity in identifying the taxa of non-parasitic leeches of the family Erpobdellidae was the main goal of this study. To this end, various bioinformatic approaches to DNA sequence analysis have been tested. As a result, the phylogenetic diversity amounted to 47 species versus 29 morphospecies defined traditionally. The use of molecular species delimitation methods made it possible to identify seven complexes of morphologically hidden (cryptic) species and some morphological misidentifications, as well as to discover a new species from Eastern Siberia (Erpobdella sibirica) with a unique molecular diagnosis (DNA barcode). A pioneering attempt to apply the same approach to higher taxa showed that Erpobdellidae probably consists of seven genera, including the unambiguous elimination of the genus Motobdella. Obtaining quantitative and, therefore, objective data is an advantage of the molecular approach, which has proven to be effective in recognizing species and genera, at least in leeches.