Potential Himalayan community turnover through the Late Pleistocene

Prevailing models for the high biodiversity in tropical mountains assume that organisms can survive through past climate change by performing short elevational movements to track suitable habitats. However, dramatic Pleistocene climatic oscillations could also lead to species turnover but have widely been ignored. Here, we used ecological niche modelling (ENM) of 288 passerine species in the Himalayas to test the effect of climate change during the Last Interglacial Period (LIG), the Last Glacial Maximum (LGM) and the present day. The ENM analyses hindcasted species persistence through climate change from the LGM to the present day but likely showed a high degree of species turnover (e.g. 32.6–46.2%) from the LIG to the LGM. Further elevational dynamic reconstructions demonstrated that species might survive these two periods of climate change by upward and downward shifts, respectively. Statistical analyses of climatic variables showed increased climatic variability in the Himalayas during the LIG, which might have caused community turnover. The severe evolutionary consequence of the LIG climate in the Himalayas contrasts with the paradigm of the climatic optimum in Europe and North America and suggests potential geography-dependent effects of past climate change. More importantly, our results demonstrate that dramatic historical climate change might overwhelm the buffering effect of elevational heterogeneity, which should be considered when investigating the origin of tropical montane biodiversity.