Interglacial refugia and range shifts of the alpine grasshopper Stenobothrus cotticus (Orthoptera: Acrididae: Gomphocerinae)

A warming climate leads to shifts in distribution ranges to higher latitudes and altitudes. Consequently, cold-adapted alpine species can be trapped in interglacial Holocene refugia on high mountain summits if they fail to expand their ranges to the north. One example is the alpine grasshopper Stenobothrus cotticus . This species was assumed to be endemic to the southwestern Alps (France, Italy). However, we have found a second refugium in the Rila Mountains in southwestern Bulgaria. Analyses of the mitochondrial gene co1 and of phenotypic characters from morphology and behaviour did not reveal differences between the two geographically separated populations of S. cotticus studied. We suppose that S. cotticus had a wider distribution during colder periods, when its range was expanded to lower altitudes. This hypothesis is supported by the current distribution of the closely related montane S. rubicundulus .