Budaeva N.E., Rogacheva A.V. 2013. Colonization of the Arctic Ocean by two cosmopolitan genera of marine invertebrates // Invertebrate Zoology. Vol.10. No.1: 127–142 [in English].
KEY WORDS: Paradiopatra, Elpidia, phylogeny, biogeography, trans-Arctic interchange.
ABSTRACT: The colonization of the Arctic Ocean by two genera of marine invertebrates widely-distributed outside the Arctic, Paradiopatra, a polychaete, and Elpidia, a holothurian, is described using methods of phylogenetic biogeography, including morphology-based phylogenetic reconstruction. The phylogeny of Elpidia was reconstructed based on a matrix of 20 morphological characters for 22 species. Maximum parsimony analysis yielded four equally parsimonious trees within the Arctic clade, comprising three species: E. belyaevi, E. glacialis and E. heckeri. Elpidia gracilis inhabiting the north Atlantic was the sister species to the Arctic clade on three of four most parsimonious tress. This suggests possible colonization of the Arctic Ocean from the North Atlantic. Comparison of pairs of species of Paradiopatra: P. striata/P. pauli and P. yasudai/P. quadricuspis supports the hypothesis of trans-Arctic faunal exchange. These pairs form monophyletic clades on the strict consensus tree and have representatives in the Pacific and the Arctic/North Atlantic. It is argued that dispersal of fauna most probably was directed from the north Pacific to the North Atlantic across the Arctic. Two North Atlantic species, P. fiordica and P. quadricuspis, with almost identical geographical and vertical ranges along the boundary between the North Polar Region and the Eastern Atlantic Boreal Region did not form the monophylectic clade on the phylogenetic tree and were considered as distant relatives. However the strict consensus tree had very low resolution due to high portion of homoplastic characters and relationships of the species could not be tested exhaustively.