Genotype-Environment Interaction for Climate and Competition in a Natural Population of Flour Beetles, Tribolium castaneum

Abstract

The norm of reaction, the set of average phenotypes produced by a genotype in different environments, can be affected by spatial variation in natural selection especially when there exists genotype‐environment interaction. In subdivided populations, the greater the genotype‐environment interaction variance and the lower the migration rate, the more independent are the possible evolutionary trajectories for local adaptation. I examined genotype‐environment interaction in the rate of population increase for lineages randomly derived from a wild population of Tribolium castaneum across a series of ecologically important environments. The lineages were derived from an outbred, wild‐caught population by 14 generations of random genetic drift, during which the effective size of each lineage was approximately 22 breeding adults. The environments studied were the classic temperate‐wet and cold‐dry climates of Park (1954) in factorial combination with two genetic strains of a congeneric competitor, T. confusum. Much among‐lineage genetic variation for rate of population increase was found for each of these ecologically important environments of climate and competition. Genotype‐environment interaction accounted for 40.5% of the total among‐lineage variance in rate of population increase signifying that the performance of a lineage in one environment is not necessarily a good predictor of its performance in another. Changing the genetic identity of the competitor changed the rate of increase of some lineages as much or more than changing the climatic conditions of temperature and humidity. This is the first empirical study to characterize the genotype‐environment interaction variance associated with genetic variation in a competing congeneric species. This competitor‐specific genetic variation in competitive ability may play an important role in coevolution in subdivided populations.

Genetic Effects at Pleiotropic Loci Are Context-Dependent with Consequences for the Maintenance of Genetic Variation in Populations

“…X k and SD k are the mean and standard deviation of the k th cohort, and SD pooled is the average SD over all cohorts. This standardization removes the effect of differential dispersion of cohorts' means, hence eliminating the differences in the scale of the genotypic effects and leaving only the changes in the order of the genotypic means as the source of the interaction [57], [94]. These transformed trait values were analyzed by the mixed model in SAS as described above.…”

Adaptation of the gypsy moth to an unsuitable host plant

“…Although most studies clearly demonstrate that cross-environment genetic correlations for fitness related traits are often less than +1, which indicate 'crossing of reaction norm for fitness' , some authors (e.g., Service, 1984;Wade, 1990;Sultan & Bazzaz, 1993) hold that trade-offs neverthe-less exist. Namely, the absence of a genotype with maximal fitness in different environments, which is evidenced by r G < +1, requires that at least at one gene, selection favours different alleles in different environments (i.e., that 'trade-offs' exist).…”

Evolutionary Potential and Local Genetic Differentiation in a Phenotypically Plastic Trait of a Cyclical Parthenogen, Daphnia magna

“…For instance, Boileau et al (1992) have convincingly shown that founder effects can be very long lasting. In contrast, a number of studies on the genetic variation in ecologically relevant traits have indicated a high degree of localized adaptation (e.g., Ayre 1985;Schmitt and Gamble 1990;Wade 1990;Malhorta and Thorpe 1991;Via 1994). It should be emphasized that both types of studies are complementary and that the differences in result are most probably the outcome of the focus on neutral markers versus ecologically relevant traits itself.…”