Sunius brevipennis ( WOLLASTON 1864)

Assing, V. & A, North, 2008, A revision of the Sunius species of the Western Palaearctic region and Middle Asia (Coleoptera: Staphylinidae: Paederinae), Linzer biologische Beiträge 40 (1), pp. 5-135 : 35

4.8. Sunius brevipennis ( WOLLASTON 1864)

C o m m e n t s: A comparative study of material from Tenerife, Gran Canaria, La Gomera, La Palma, and El Hierro revealed that the species is polymorphic regarding various external characters (coloration, eye size, microsculpture of the head, eye size, length of elytra and hind wings) and even the shape of the ventral process of the aedeagus. Furthermore, the populations from the different islands display – to some extent – distinct character combinations. Regarding the external characters, however, there is considerable variation within, and there is some overlap between populations. These observations suggest that there is no – or only negligible – gene flow between populations and that they are species in statu nascendi, a hypothesis to be confirmed e. g. by molecular data. The fact that the differences in the morphology of the aedeagus are only weakly pronounced is not surprising and is no argument to the contrary, considering that they are slight also between species distinguished by conspicuous external differences (e. g. S. brevipennis , S. microphthalmus , and S. tenerifensis ). Among Canarian Staphylinidae , similar examples of assemblages of closely related, allopatric (sub-)species with weakly pronounced character divergence are known, for instance, from Astenus DEJEAN 1833 ( Paederinae ), Othius STEPHENS 1829 ( Staphylininae ), and from the subgenus Canaroxypoda ZERCHE 1996 (ASSING 1997; ISRAELSON 1971; ZERCHE 1996).

Based on the morphology of the aedeagus, three entities can be distinguished, two of which have names already: one from Tenerife ( S. brevipennis ), one from Gran Canaria, La Palma, El Hierro, and Lanzarote ( S. canariensis ), and one from La Gomera. They are here regarded as subspecies of S. brevipennis .

Based on the external and sexual characters, all the Sunius species occurring in the Canary Islands refer to the S. melanocephalus species group. The similar morphology especially of the male primary and secondary sexual characters suggests that the Canarian representatives form a monophyletic group and that, consequently, the diversity of Canarian Sunius is the result of one successful colonisation event with subsequent speciation.