Signatures of range expansion and erosion in eastern North American trees.

Abundance and occupancy of populations at high- and low-latitude geographic range edges will be critically important in determining a species' response to climate change. Low abundance and occupancy at expanding (high latitude) edges of the range may limit a species capacity to migrate, and at trailing (low latitude) edges, may result in range erosion and regional extinction. We examined abundance-occupancy distributions across the geographic ranges of 102 eastern North American trees and looked for signatures reflecting capacity to respond to climate change. We found that 62% of species display a signature consistent with higher climatic suitability in the northern latitudes of their range. However, our results suggest that the most common response is likely to involve range erosion in the south and limited range expansion in the north, possibly leading to an overall reduction in range size for many species. In particular, species with smaller ranges centred at lower latitudes may not have the capacity to successfully track the current rate of climate change.