Environmental stress and evolutionary change

Periodically, populations will experience stressful conditions. Adaptation to these conditions requires adequate levels of heritable genetic variance. Other factors including genetic interactions and gene flow may also prevent evolutionary responses. Although stressful conditions can lead to a loss of biodiversity following extinction, periods of stress may also lead to rapid evolution and diversification through novel/intense selection pressures and through the release of variability following an increase in mutation and recombination rates and/or the disruption of canalized systems. Over the last century, anthropogenic disturbances have increasingly imposed severe and novel environmental stresses on natural populations. Evolutionary shifts in response to these recent disturbances (including climate change) have already been detected as shifting phenotypes and altered allele frequencies along gradients.