Morphological and molecular species delimitation within the Holarctic Ilybius angustior complex with a focus on Beringia (Coleoptera: Dytiscidae)

Abstract

A fourth species of the Holarctic Ilybius angustior complex, Ilybius minakawai n. sp., is described from the Island of Sakhalin in the Russian far east. Male genitalia are diagnostic within this species complex, although from body size and shape the new species cannot be separated from I. churchillensis Wallis from north Alaska and the Canadian low arctic. The small and narrow body characteristic of these two species represents an extreme of the cold climate form of the widespread I. angustior (Gyllenhal). Low variation within the studied large ribosomal and cytochrome c oxidase subunit I mitochondrial genes suggest that speciation events within the I. angustior-complex are fairly recent. In combination with known geographical ranges, the low genetic variation within this species complex suggest speciation within Pleistocene refugia including Beringia.

Keywords:

• Diving beetles
• Ilybius angustior
• new species
• Holarctic
• mitochondrial DNA
• species delimitation
• Sakhalin

Acknowledgements

David J. Larson, St. John's, is thanked for sharing his morphometric raw data. Johannes Bergsten, Umeå, David Bilton, Plymouth, Lars Hendrich, Berlin, and Bert Viklund, Stockholm, are all thanked for the loan of specimens. Sergey K. Kholin and Noboru Minakawa are both thanked for sending specimens they collected. Ana Izquierdo (MNCN, Madrid) is thanked for sequencing work. Sequences of NHM specimens were obtained in the laboratory of Alfried Vogler. Molecular work was financed through the project CGL2004-00028 to IR.