Genic Variability and Strategies of Adaptation in Animals

Abstract

Levels of genie heterozygosity, as measured by surveys of allozymic variation, are much lower in populations of large, mobile animals (most vertebrates) than in those of small, relatively immobile animals (most invertebrates). This difference is not consistent with theories relating variability to population size (species number) or dispersal ability (gene flow), but it is predicted by Levins' theory of adaptive strategies in relation to environmental uncertainty ("grain"). Mobility and degree of homeostatic control apparently are important factors influencing levels of genic heterozygosity in natural populations. The results argue indirectly that at least a major proportion of allozymic variation is maintained by natural selection.

Genetic variability and environmental variability in the estuarine isopod Sphaeroma rugicauda

“…This does not support the "hetero selection" theory of Grasslé (1972) nor the general idea of Levins (1969) that levels of genetic variability are determined by environmental variability. The results also contradict the prediction of Selander and Kaufman (1973) that body size and levels of genetic variability are negatively correlated. Differences in the seasonal pattern of trophic resource availability will be negligible between two sites at essentially the sathe latitude rendering this an unlikely explanation.…”

“…Large individuals will therefore experience a harsh and variable environment as less stressful than will small animals as Selander and Kaufman (1973) proposed. Not only are mortality rates overall related to size but so are the fitness differences.…”

Biochemical variation in roe deer (Capreolus capreolus L.): are r-strategists among deer genetically less variable than K-strategists?

“…While our results support Nevo's (1984) conclusion that generalist species are genetically more variable than specialist species they provide further evidence against the argument that comparatively large mammals should be genetically less variable than small mammals. This argument was mainly derived from the "environmental grain hypothesis" proposed by Selander and Kaufman (1973) and supported by first electrophoretic studies on large mammals (see e.g. Cameron and Vyse, 1978;Simonsen, 1982).…”

Lack of biochemical polymorphism in British fallow deer

“…We know of no convincing selectionist theory predicting a low level of genetic variation in the fallow deer compared with other deer species. The "environmental grain" hypothesis of Selander and Kaufman (1973), which predicts low levels of variation in large, highly mobile species and vice versa has attracted some interest in the literature (e.g., Cameron and Vyse, 1978) but was not supported by a recent interspecific comparison of large grazing mammals (Baccus et aL, 1983). Presumably the environmental grain hypothesis would predict a higher level of variation in fallow deer than in moose, red deer and wapiti, which is not borne out by our findings.…”