Contemporary patterns of species distributions are influenced by both current and historical conditions. Historically unstable climates can lead to reductions in species richness, when species go extinct because they cannot track climate changes, when dispersal limitation causes species to fail to fully occupy suitable habitat, or when local diversification rates are depressed by local population extinctions and changing selective regimes. Locations with long-term climate instability should therefore show reduced species richness with small-ranged species particularly missing from the community. We used a novel measure of climate stability, climate change velocity, which combines information on temporal and spatial gradients in climate to describe the rate at which a particular climate condition is moving over the surface of the Earth. Climate change velocity since the Last Glacial Maximum is likely to be a more biologically meaningful measure of climate stability than the previously used simple climate anomaly, because it scales climate change relative to local variation in climate, capturing the potential for topographic refuges to buffer species from climate change. We tested these predictions using global data on mammal and amphibian distributions. Consistent with our predictions, richness of small-ranged species of both groups was negatively associated with velocity. Velocity generally explained more variation in richness than did the simple climate anomaly. Climate velocity appears to capture an important historical signal on current mammal and amphibian distributions.
Climate change; Climate velocity; Mammals; Amphibians; Endemism; Diversity; Range size
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5th biennial conference of the International Biogeography Society, 2011