When Grinnellian generalist species seem to be more sensitive to altered habitats than specialists: the case of Orthoptera communities settled in coastal dunes

Summary Numerous examples documented that species generalists for habitats are less sensitive to altered environment than specialists. However, in arid environments, an example indicated an opposite trend due to special adaptive features of organisms. We tested this hypothesis in the case of grasshopper communities, settled in the coastal dunes of northeast Algeria, as several aspects of dunes constitute stressful conditions resembling those of deserts. To define the dune-specific grasshoppers (specialists) and the dune non-specific ones (generalists), we applied the indicator value index to monthly samplings conducted in four coastal dune sites and 12 other sites of grasslands, fallow lands and scrublands in the same area. The degree of disturbance of each coastal dune site was deduced from the alteration of plant cover and richness. We investigated the relation between the specialist and generalist richness and abundance with the degree of perturbation using linear regressions. Results showed contrasting patterns for specialist and generalist grasshoppers: both abundance and richness of the generalists significantly decrease with an increasing degree of perturbation, while specialists show little to no changes. The higher resistance of specialist grasshoppers over generalists toward disturbance was not linked to the plant dune-specialists or generalists. This study is one of very few illustrating the relative resistance of specialized species toward disturbance.