Retreating or Standing: Responses of Forest Species and Steppe Species to Climate Change in Arid Eastern Central Asia

Climate change  affects species distributions and their lineage evolution in many parts of the world. Addressing the impacts of climate change on the distribution and genetic structure of species has become an active field of research in historical biogeography and global change biology. As one of the most widespread landscape types in the world, arid land is well known to have experienced a series of climate changes during the Quaternary, which have strongly influenced the distribution and evolution of organisms. In the future, climate changes are similarly projected to occur in arid land, so information is needed to predict the range shifts and genetic responses of plant species to climate changes.

Eastern Central Asia is far from oceans and highlighted as a typical temperate arid region. To investigate the effect of climate change on plant species in arid Eastern Central Asia, ZHANG Hongxiang et al. selected two widespread species Clematis sibirica and C. songorica as candidates from montane coniferous forest and arid steppe habitats respectively. C. sibirica is a woody perennial vine that grows primarily under conifer forests, while C. songorica is a small perennial shrub occurring in the steppe and on gravelly slopes..

In this study, a combined approach of molecular phylogeography and species distribution modelling (SDM) was used to predict the future responses of these two species to climate change. The results show that genetic data for C. sibirica shows a significant phylogeographical signal (N_ST>F_ST, P<0.05) and demographic contraction during the glacial-interglacial cycles in the Pleistocene. This forest species would likely experience range reduction, though without genetic loss, in the face of future climate change.

In contrast, SDMs predict that C. songorica, a steppe species, should maintain a consistently stable potential distribution under the Last Glacial Maximum and the future climatic conditions referring to its existing potential distribution. Molecular results indicate that the presence of significant phylogeographical signal in this steppe species is rejected and this species contains a high level of genetic differentiation among populations in cpDNA, likely benefiting from stable habitats over a lengthy time period.

Evidence from the molecular phylogeography of these two species indicates that the forest species is more sensitive to past climate changes than the steppe species. SDMs also predict that the forest species will face the challenge of potential range contraction in the future more than the steppe species. This provides a perspective on ecological management in arid Eastern Central Asia, indicating that increased attention should be paid to montane forest species, due to their high sensitivity to disturbance. The result was published in PLOS ONE on 15 April 2013.