Macroptery in Altitudinal Specialists Versus Brachyptery in Generalists-A Paradox of Alpine Scandinavian Carabid Beetles (Coleoptera: Carabidae)

Abstract

Non-riparian alpine carabid beetle assemblages in Scandinavia are usually dominated by a set of seventeen species. Five of these species are more or less restricted to the alpine and subalpine regions (altitudinal specialists), whereas the remaining twelve species are widespread also in lowland (altitudinal generalists). Flight-wing length differs between these two groups of species, i.e. all altitudinal specialists are macropterous, whereas seven of the generalists are brachypter- ous or dimorphic with the brachypterous morph strongly dominating. Generalists abundant in lowland forests are all brachypterous, whereas the macropterous species in lowland are confined to open, dry habitats. The dominance of macroptery among altitudinal specialists is paradoxical as the alpine environment generally is supposed to select for brachyptery, and the specialists should be better adapted to their habitat than the generalists are. Available subfossil evi- dence suggests that the specialist species reached the Scandinavian Mountain Range from a continental refugium south of the ice sheet. The macroptery of the specialists can be explained by the relative recentness of the last glaciation and the lower dispersal power of the brachypterous or apterous tundra species that have not been able to colonize Scandinavia from their glacial refugia. The time available for colonization of generalist species following deglaciation was probably much longer than for specialists, and consequently brachypter- ous species were successful. Wing dimorphism as a tool for reconstructing faunal history is discussed.