What do we mean by 'refugia'?

The term ‘refugia’ was originally used to describe the restricted full-glacial locations of modern mid- and high-latitude taxa, especially trees and shrubs. We discuss the extension of this original use to other situations, including its widening to encompass ‘interglacial refugia’. Recent genetic work with modern populations suggests that, at the glacial–interglacial transition, those taxa that did vastly increase their ranges and abundances did so from a small subset of their full-glacial populations. We suggest that ‘bottleneck’ might be a more appropriate term to use for temporarily reduced populations, to indicate continuity of the populations, and that individualistic response of taxa to climate change appears to extend to intra-specific levels. The extent to which expanded populations contribute to long-term genetic pools remains uncertain.