Meeting Abstract
Harsh environments and severe winters have been hypothesized to favor improved cognitive abilities used for successful foraging. Geographic variation in winter climate, then, is likely associated with differences in selection pressures on cognitive ability, which could lead to evolutionary changes in cognition and its neural mechanisms. As predicted under natural selection, two species of food-caching chickadees, which depend on stored food to survive winter and rely on spatial memory to recover their stores, exhibit extensive climate-related population variation in spatial memory and the hippocampus. Such population variation, however, could be driven by several potential mechanisms including natural selection, environment- and experience-based plasticity, and/or epigenetic differences. Extensive data on cognition and brain morphology in multiple populations along longitudinal, latitudinal and altitudinal winter climate gradients are consistent with the hypothesis that natural selection drives population-level differences in spatial memory. To date, however, there is no support for the hypotheses that environment-induced plasticity or developmental differences are the main causes of population differences across climate gradients. Available published data on epigenetic modifications of memory ability are also not consistent with the observed patterns of population variation, with birds living in more stressful and harsher environments having better spatial memory, larger hippocampus and larger number of hippocampal neurons. Overall, existing data indirectly suggest that differences in winter climate drive the evolution and maintenance of population differences in cognition and the brain via natural selection, at least in food caching parids.
