The immediate capacity for adaptation under current environmental conditions is directly proportional to the additive genetic variance for fitness, VA(W). Mean absolute fitness, (Formula presented.), is predicted to change at the rate (Formula presented.), according to Fisher's Fundamental Theorem of Natural Selection. Despite ample research evaluating degree of local adaptation, direct assessment of VA(W) and the capacity for ongoing adaptation is exceedingly rare. We estimated VA(W) and (Formula presented.) in three pedigreed populations of annual Chamaecrista fasciculata, over three years in the wild. Contrasting with common expectations, we found significant VA(W) in all populations and years, predicting increased mean fitness in subsequent generations (0.83 to 6.12 seeds per individual). Further, we detected two cases predicting “evolutionary rescue,” where selection on standing VA(W) was expected to increase fitness of declining populations ((Formula presented.) < 1.0) to levels consistent with population sustainability and growth. Within populations, inter-annual differences in genetic expression of fitness were striking. Significant genotype-by-year interactions reflected modest correlations between breeding values across years, indicating temporally variable selection at the genotypic level that could contribute to maintaining VA(W). By directly estimating VA(W) and total lifetime (Formula presented.), our study presents an experimental approach for studies of adaptive capacity in the wild.
- Adaptive capacity
- Chamaecrista fasciculata
- Fisher's Fundamental Theorem of Natural Selection
- aster models
- genotype-by-environment interactions
PubMed: MeSH publication types
- Journal Article