Six species in one: evidence of cryptic speciation in the Hygrobates fluviatilis complex (Acariformes, Hydrachnidia, Hygrobatidae)

Abstract

Water mites of the genus Hygrobates are widely distributed in all biogeographic regions except the Antarctic. Palaearctic Hygrobates species with reticulated soft integument generally have been considered as representatives of one common and widely distributed species, Hygrobates fluviatilis Strøm, 1768. Based on partial COI sequences (DNA-barcodes) and statistical analysis of morphological data, we show that these mites belong to six distinct lineages. Two of them are widely distributed in Central Europe: Hygrobates fluviatilis here redescribed based on a neotype designated from the type locality in Norway, and a species new to science, H. arenarius Smit & Pešić. The four remaining lineages represent additional species new to science that appear to have more restricted distributions: H. corsicus Pešić & Smit (Corsica, Sardinia), H. marezaensis Pešić & Dabert (Montenegro, Albania, Croatia), H. turcicus Pešić, Esen & Dabert (Turkey), and H. persicus Pešić & Asadi (Iran, E Turkey). Statistical morphometric analysis reveals that the latter two species cannot be separated on morphological characters and should be considered true cryptic species. We provide data concerning biology and geographical distributions together with a key to all species of the complex.