Heritability of wing development and body size in a carabid beetle, Pogonus chalceus MARSHAM, and its evolutionary significance.

The wing-polymorphic ground beetle Pogonus chalceus MARSHAM was subjected to crossbreeding experiments under different laboratory conditions in order to estimate the genetic and environmental contributions to the total phenotypic variance in different morphological traits related to relative wing development and body size. Heritability of relative wing development appears to be strong. Beetle size also seems genetically determined in some cases, but separation of male and female parent contribution invariably shows a maternal effect. These results are tested in a breeding experiment with a high number of progeny from one parental pair, reared at two temperatures and at two levels of food supply. Relative wing development is not influenced by these environmental conditions, as expected, but different temperatures add significant variance to the body size values. The experimental results are used to explain interdemic variation in these morphological traits, as observed in three isolated field populations. The reproductive effort under optimum breeding conditions is higher in macropterous beetles than in beetles with reduced wings, but this could result from their larger body size. Migtion seems to be the most plausible underlying evolutionary mechanism for the observed wing reduction in older populations.