Shifting latitudinal clines in avian body size correlate with global warming in Australian passerines

摘要

Intraspecific latitudinal dines in the body size of terrestrial vertebrates, where members of the samespecies are larger at higher latitudes, are widely interpreted as evidence for natural selection and adap-tation to local climate. These dines are predicted to shift in response to climate change. We usedmuseum specimens to measure changes in the body size of eight passerine bird species from south-easternAustralia over approximately the last 100 years. Four species showed significant decreases in body size(1.8-3.6% of wing length) and a shift in latitudinal cline over that period, and a meta-analysis demon-strated a consistent trend across all eight species. Southern high-latitude populations now display thebody sizes typical of more northern populations pre-1950, equivalent to a 7° shift in latitude. Usingptilochronology, we found no evidence that these morphological changes were a plastic response tochanges in nutrition, a likely non-genetic mechanism for the pattern observed. Our results demonstratea generalized response by eight avian species to some major environmental change over the last 100 yearsor so, probably global warming.