Global patterns of connectivity and isolation of populations of forest bird species in the late Pleistocene

Aim: Species' distributional responses to cool periods in the Pleistocene appear to have been diverse, but patterns of response are poorly known globally, and the nature of distributional responses to interglacial conditions remains largely unknown. The aim of this contribution is to assess distributional responses of forest bird species to Last Interglacial (LIG) and Last Glacial Maximum (LGM) conditions within nine forest regions world-wide, to test whether different regions experienced consistently different types of distributional responses. Location: Global. Methods: We use ecological niche modelling approaches under an assumption of ecological niche conservatism to assess degrees of fragmentation of species distributions through the LIG–LGM–present transitions. Models trained under presentday conditions were transferred to Pleistocene conditions, and fragmentation of potential distributional areas was assessed using FragStats. Results: Our results showed four regions to have greater fragmentation at LGM than at LIG or at present; three showed greater connectivity at LGM; and two were equivocal. Main conclusions: Our results suggest that the world is a patchwork of regions in which forest species experienced either consistently greater or consistently lesser population subdivision during the alternating cool and warm periods that characterized the Pleistocene. Speciation timing and dynamics should differ dramatically among major regions and biomes if these periods of connection and disjunction translate into speciation opportunity.