Climate change is predicted to negatively impact wildlife through a variety of mechanisms including retraction of range. We used data from the North American Breeding Bird Survey and regional and global climate indices to examine the effects of climate change on the breeding distribution of the Rusty Blackbird (Euphagus carolinus), a formerly common species that is rapidly declining. We found that the range of the Rusty Blackbird retracted northward by 143 km since the 1960s and that the probability of local extinction was highest at the southern range margin. Furthermore, we found that the mean breeding latitude of the Rusty Blackbird was significant and positively correlated with the Pacific Decadal Oscillation with a lag of six years. Because the annual distribution of the Rusty Blackbird is affected by annual weather patterns produced by the Pacific Decadal Oscillation, our results support the hypothesis that directional climate change over the past 40 years is contributing to the decline of the Rusty Blackbird. Our study is the first to implicate climate change, acting through range retraction, in a major decline of a formerly common bird species.

The distribution of diversity along latitudinal and elevation gradients, and the coupling of this phenomenon with climate, is a pattern long recognized in ecology. Hypothesizing that climate change may have altered this pattern over time, we investigated whether the aggregate of reported northward shifts of bird ranges in North America is now detectable in community-level indices such as richness and diversity. Here, we report that bird diversity in North America increased and shifted northward between 1966 and 2010. This change in the relationship of diversity to the latitudinal gradient is primarily influenced by range expansions of species that winter in the eastern United States as opposed to species which migrate to this area from wintering grounds in the tropics. This increase in diversity and its northward expansion is best explained by an increase in regional prebreeding season temperature over the past 44 years.

No abstract

The study of the early stages of speciation can benefit from examination of differences between populations of known history that have been separated for a short time, such as a few thousands of generations. We asked whether two lines of Drosophila melanogaster that were isolated more than 40 years ago have evolved differences in life-history characters, or have begun to evolve behavioural or postzygotic isolation. One line, which is resistant to DDT, showed lower egg production and a shorter lifespan than a susceptible line. These differences are not a pleiotropic effect of resistance because they are not attributable to the chromosome that contains the resistance factors. The two lines have begun to become behaviourally isolated. Again, the isolation is not attributable to genes on the chromosome that contains resistance factors. The lines show only prezygotic isolation; there is no evidence of reduced fitness of F1 or F2 hybrids. These lines and others like them, should be excellent subjects for analyses of genetic changes that could lead to speciation.

No abstract