On the morphological separation of two sibling species: Pardosa proxima (P. vlijmi syn. nov.) and P. tenuipes (Araneae: Lycosidae)

Morphological descriptions of P. proxima (C. L. Koch, 1847) (= P. vlijmi den Hollander & Dijkstra, 1974, syn. nov.) and its sister species P. tenuipes L. Koch, 1882 (= P. proxima auct.), a pair of species hardly distinguishable on a morphological basis but easily separable through behavioural characters, are given. The identification on an ethological basis allowed us to study the morphology of the males and to point out the morphological characteristics that can be used to discriminate the two species. Moreover, the examination of type material of Pardosa proxima and P. tenuipes, together with details given in the original descriptions, led us to conclude that P. vlijmi is a junior synonym of P. proxima and that P. tenuipes has been long overlooked. However, females remain hard to distinguish due to high intraspecific variability in the shape of the epigyne, vulva and habitus. According to the examination of material from different parts of Europe, P. proxima seems to be quite common in Italy and in the south of the Balkan Peninsula (mainly Greece and Bulgaria) while P. tenuipes is more widely distributed in western Europe, reaching central Europe. Contact zones between the two species were found in northwestern Italy and France. Far from detailing the precise distribution of the two species, we suggest that material previously identified as “Pardosa proxima” should be checked for establishing the occurrence of one or both species in different countries.