Sympatry and colour variation disguised well-differentiated sister species: Suphrodytes revised with integrative taxonomy including 5 kbp of housekeeping genes (Coleoptera: Dytiscidae)

Abstract

The genus Suphrodytes, is currently regarded as a monobasic Palearctic genus with one colour-variable species, S. dorsalis. Here we show with >5 kbp of nuclear and mitochondrial genes and quantitative morphological characters that Suphrodytes consists of two well-defined species, albeit each with variable colour pattern. The primary barcode gene CO1, showed consistent signs of multiple copies, therefore a range of alternative housekeeping genes were screened for information. The two species were reciprocally monophyletic in genetrees from 12S, 16S, CO1, CO2, CytB, H3 and 18S. Explicit species delimitation tests based on the coalescent process model rejected the null hypothesis that the genealogies originated from a single panmictic species. The mitochondrial proteincoding genes were proportionally richest in information followed by 12S and Histone 3. Conservative nuclear 18S had a single fixed diagnostic character. The two species were significantly different in total bodylength, bodyshape, shape of the male aedeagus and parameres. We review the taxonomic literature of Suphrodytes and find S. dorsalis (Fabricius, 1787) and S. figuratus (Gyllenhal, 1826) to be the oldest available names for the respective species, and for which we designate lectotypes. Synonyms are established for both species which are broadly sympatric across the Palearctic and frequently even collected at the same locality.