Revisiting Adaptive Potential, Population Size, and Conservation

Additive genetic variance (V_A) reflects the potential for evolutionary shifts and can be low for some traits or populations. High V_A is critical for the conservation of threatened species under selection to facilitate adaptation. Theory predicts tight associations between population size and V_A, but data from some experimental models, and managed and natural populations do not always support this prediction. However, V_A comparisons often have low statistical power, are undertaken in highly controlled environments distinct from natural habitats, and focus on traits with limited ecological relevance. Moreover, investigations of V_A typically fail to consider rare alleles, genetic load, or linkage disequilibrium, resulting in deleterious effects associated with favored alleles in small populations. Large population size remains essential for ensuring adaptation.