Landscape-scale Expansion of Roesel's bush-cricket Metrioptera roeselii at the North-western Range Limit in Central Europe (Orthoptera: Tettigoniidae)

摘要

Range expansion linked to global warming is a widespread phenomenon among insects. This range expansion may be either gradual and on a broad-front or discontinuous following long distance dispersal. Many species of Orthoptera show a distinct wing-length dimorphism related to dispersal and rare long-wing individuals are assumed to contribute significantly to the colonisation of new habitat patches. Grid-based distribution surveys of Roesel's bush cricket Metriopera roeselii (Hagenbach 1822) at the edge of the species' range in NW' Germany were conducted in 1991, 1996 and 2004. Most newly colonised grid cells were directly adjacent to cells that were occupied in previous surveys or were connected to them by other colonised cells. The maximal distance between newly colonised grid cells and cells that were occupied in previous surveys was 6.3 km between 1991 and 1996 and 5.1 km between 1996 and 2004. The proportion of macropterous individuals sampled in 2004 was very low (1.4%). Macropterous individuals tended to occur in newly colonised, more isolated and low abundance grid cells. Hence, range expansion of M roeselii took place by short-distance colonisation from cells that were occupied in previous surveys rather than by single events of long-distance dispersal.