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The immediate capacity for adaptation under current environmental conditions is directly proportional to the additive genetic variance for fitness, V-A(W). Mean absolute fitness, W over bar , is predicted to change at the rate VA(W)W over bar , according to Fisher's Fundamental Theorem of Natural Selection. Despite ample research evaluating degree of local adaptation, direct assessment of V-A(W) and the capacity for ongoing adaptation is exceedingly rare. We estimated V-A(W) and W over bar in three pedigreed populations of annual Chamaecrista fasciculata, over three years in the wild. Contrasting with common expectations, we found significant V-A(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 V-A(W) was expected to increase fitness of declining populations (W over bar < 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 V-A(W). By directly estimating V-A(W) and total lifetime W over bar , our study presents an experimental approach for studies of adaptive capacity in the wild.