Summary: Reed et al. (2013)

Environmental change is one of the primary concerns of the 21st century. It is known that environmental change alters natural selection patterns in nature, but the demographic costs of persistent directional selection in response to change has yet to be quantified. Reed et al. (2013) attempted to quantify such changes in a population of wild great tits Parus major in the Netherlands. They tested whether a climate-change induced phenological mismatch negatively affected this population, which is known to have altered laying dates in response to warmer springs. Warmer springs have exerted strong directional selection for earlier laying, however, this no longer coincides with seasonal food peak abundance. Interestingly, Reed et al. (2013) found that this mismatch does not appear to have influenced population growth. They suggest that fitness losses associated with the mismatch are counteracted by fitness gains associated with a relaxation of competition. Their results are important, as they suggest that populations may be more tolerable of climate change events and may not undergo immediate declines as originally suggested.