Ecological differentiation and changes in historical distribution of Corylus heterophylla species complex since the last interglacial

  Objective  This paper aims to discuss the historical distribution changes of Corylus heterophylla complex (Corylus heterophylla, Corylus kweichowensis, Corylus yunnanensis) since the last interglacial, and understand the response mechanism of its geographical distribution to environmental evolution, so as to provide reference for clarifying the evolutionary relationship of three species, and also provide scientific basis for resource protection and development.

  Method  Based on the distribution data of the three species of C. heterophylla complex and the corresponding environmental variables, MaxEnt model and ArcGIS software were used to simulate their potential distribution in the last interglacial, last glacial maximum, mid-Holocene and modern times to explore its historical distribution changes; then, the distribution areas of three related species in different periods were superimposed to speculate their ice age refuge, which was verified by hazel pollen data. Finally, the niche differentiation among the three related species was detected by principal component analysis, and the main environmental impact factors were comprehensively evaluated.

  Result  On the whole, the contribution of the first two environmental factors affecting the distribution of C. heterophylla and C. kweichowensis was similar, while the first two main environmental factors of C. yunnanensis were related to water. Compared with temperature, water had a more important impact on the distribution of the three tree species. In terms of the suitable areas, C. heterophylla of northern China experienced glacial contraction and interglacial expansion during the quaternary, whereas C. kweichowensis and C. yunnanensis of southern China presented population expansion even during the last glacial maximum. The refuges of the three related species obtained after overlapping of the suitable areas were in good agreement with the palynological results.

  Conclusion  This study accurately simulates the distribution changes of C. heterophylla complex in four historical periods, explores its ecological differentiation, and speculates on its biological refuge, which provides some scientific basis for the conservation and management of the resources in China under the background of future climate change.