It is clear that climate shifts affect many individual species, but less clear what the net result is for ecological assemblages. β-diversity within a community over time at a given site can provide an index of the degree to which community composition has changed. An advantage of this metric is that it integrates the traits of many species. We investigated temporal β-diversity patterns between two time periods, 1950-1959 (the 1950s) and 2000-2011 (2000s). We created stacked, binary, decadal mean, species climate-space SDM’s for 282 bird species of the conterminous United States in each time period and used generalized additive models to associate the resulting temporal β-diversity with changes in decadal mean climate variables.
We found that β-diversity was primarily driven by community turnover (i.e. species replacement). Patterns in β-diversity and community turnover were strongly associated with changes in precipitation, especially annual average precipitation, and precipitation of the driest quarter, while community nestedness (i.e. species gain/loss), a second component of β-diversity, was most associated with changes in annual precipitation and precipitation of the wettest quarter. Among migratory guilds, the highest changes in species richness occurred among Neotropical migrants, suggesting that these species contributed disproportionately to overall β-diversity. Our results suggest that changes in suitable climate space for bird communities between the 1950s and 2000s was primarily due to change in Neotropical species distributions and was most associated with changes in precipitation patterns between decades.