WING-LENGTH DETERMINATION IN 2 WING-DIMORPHIC CALATHUS SPECIES (COLEOPTERA, CARABIDAE)

Wing dimorphism in the carabid beetles Calathus cinctus and C. melanocephalus was studied by rearing offspring of single-pair crosses. In both species wing dimorphism was found to be determined genetically according to a single-locus model with brachyptery dominant to macroptery. In melanocephalus, however, the expression of the long-winged genotype is modified by environmental factors such as temperature and food supply, whereas in cinctus wing-length is independent of these factors. Moreover, in melanocephalus the expression of the long-winged genotype was found to be favoured by relatively better environmental conditions (higher temperatures and abundant food) and to be more frequent in females than in males, both in the field and in laboratory experiments. It is argued that the resulting differences in phenotypic plasticity of the long-winged genotype (none in cinctus and a varying amount in melanocephalus) contribute to temporal and spatial differences in dispersal abilities between the two species. The adaptive significance of the two types of inheritance is discussed.