Expression of additive genetic variance for fitness in a population of partridge pea in two field sites

Abstract

Despite the importance of adaptation in shaping biological diversity over many generations, little is known about populations’ capacities to adapt at any particular time. Theory predicts that a population's rate of ongoing adaptation is the ratio of its additive genetic variance for fitness, (Formula presented.), to its mean absolute fitness, (Formula presented.). We conducted a transplant study to quantify (Formula presented.) and standing (Formula presented.) for a population of the annual legume Chamaecrista fasciculata in one field site from which we initially sampled it and another site where it does not currently occur naturally. We also examined genotype-by-environment interactions, G × E, as well as its components, differences between sites in (Formula presented.) and in rank of breeding values for fitness. The mean fitness indicated population persistence in both sites, and there was substantial (Formula presented.) for ongoing adaptation at both sites. Statistically significant G × E indicated that the adaptive process would differ between sites. We found a positive correlation between fitness of genotypes in the “home” and “away” environments, and G × E was more pronounced as the life-cycle proceeds. This study exemplifies an approach to assessing whether there is sufficient (Formula presented.) to support evolutionary rescue in populations that are declining.