GENETIC AND ONTOGENIC VARIATION IN BEHAVIOR - ITS POSSIBLE ROLE IN THE MAINTENANCE OF GENETIC-VARIATION IN THE WING DIMORPHISM OF GRYLLUS-FIRMUS

Genetic variation may be preserved in populations by several different modes of behaviour. In this paper we examine the consequences of beha viour on genetic variation in traits that are determined by genetic fa ctors and by environmental conditions experienced during ontogeny. The particular trait considered is wing dimorphism in the sand cricket Gr yllus firmus. In this species, as is typical of wing dimorphic insects , the adult wing morph (macropterous or micropterous) is determined by both genetic constitution and the temperature experienced during a sp ecific period of nymphal development. Wing morph may thus be controlle d, in part, by the thermal preference of nymphs. The effective heritab ility of wing morphology will be increased if nymphs with a genetic di sposition to a particular wing morph select the temperature that cause s that morph to be expressed. By contrast, effective heritability will be decreased if nymphs show no preference, or nymphs select temperatu res that reduce phenotypic variation among individuals. During the per iod of ontogeny when future wing morph is sensitive to temperature, ny mphal crickets that are genetically disposed to become macropterous se lect lower temperatures than crickets that have the opposite genetic d isposition. Likewise, nymphs that are being raised under conditions pr omoting macroptery select lower temperatures than nymphs being raised under conditions favouring microptery. The consequence of this behavio ur is that genetic variation for wing morph may be masked, and hence p reserved.