engleski

Genetic diversity of earthworms (Oligochaeta, Annelida) of the genera Octodrilus Omodeo, 1956 and Octodriloides Zicsi, 1986 in Croatia

Octodrilus and Octodriloides genera represent a diverse group of lumbricid earthworms. The species are widespread throughout Europe, but the Trans-Aegean subdomain, which includes Alpine-Balkan- Carpathian region, is considered as an evolution origin. Croatian territory is one of the centers of divergence of these genera. Octodrilus includes at least 53, and Octodriloides at least 22 described species, with numerous subspecies within both genera. So far, 15 Octodrilus species (seven endemic), and five Octodriloides species (four endemic)have been recorded in Croatia. In databases(e.g. BOLD and GenBank) publicly available sequences of these genera from Croatia are almost non-existent, making this molecular research a first study of its kind in Croatia.180 specimens were isolated from several collections, sampled at 76 sites throughout Croatia. The specimens were identified to species level according to identification keys. Specimens were barcoded by isolating, amplifying and sequencing the COI region of mtDNA from the epithelial tissue of each specimen. The obtained sequences of each specimen were processed and compared, and one phylogenetic tree of both genera was constructed by the method of the highest probability. By tree analysis, according to the degree of support and genetic distance, 28 lines representing potential species and/or subspecies were separated. 25 lines were included in 13 described species. Four species form complexes of at least two lines, and three lines are unique in their dislocation from others and do not lead to the described species using identification keys due to specific morphological features or due to specimen’s juvenile stage. Consensus among published research indicates that two specimens of earthworms can be considered separate species if their genetic distance calculated by Kimura 2- parameter is greater than 15%, and if there are morphological differences between sister lines when the genetic distance value is 9-15%. The largest genetic distance between lines in this study is 25.3%, while the lowest is 11.8%. It should be noted that only one molecular marker (COI) was used in this study and it is not possible to reliably determine the hierarchical relationships of Octodrilus and Octodriloides genera species, as well as the monophyletic origin of each genus.

COI ; Octodrilus ; Octodriloides ; endemic species

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