Habitat Heterogeneity and Survival in a Bush Cricket Metapopulation

Abstract

The bush cricket, Metrioptera bicolor Philippi (Orthoptera, Tettigoniidae) lives in a restricted area with grassland patches separated by mainly pine forest. The regional population dynamics can be described as a metapopulation with local extinctions and colonizations. I used inventory data in order to test the following hypotheses: (1) temporal variability of local population size should be negatively correlated with habitat heterogeneity, when habitat quality changes in relation to fluctuating weather conditions; (2) extinction risk should be higher on homogeneous habitat patches than on heterogeneous patches. Both hypotheses are convincingly corroborated and I find a compensatory effect between patch area and heterogeneity. Local extinctions may occur on large, but homogeneous patches, and local populations can survive quite well on small patches that contain a mosaic of several types of grassland vegetation with different humid conditions. I discuss the implications of these findings for the preservation of endangered species that are susceptible to regional stochasticity.