Geographic Patterns Of Species Diversity Of Theaceae In China

The spatial distribution patterns of species diversity have been a hot topic in the field of macro-ecology and biogeography.Understanding the geographical distribution patterns of species diversity and the environmental factors that affect these patterns are one of the most important issues in biodiversity research,and also the basis of conservation biology.Theaceae is a key family in the phylogeny of angiosperms,and also a dominant and representative family of subtropical evergreen broad-leaved forest in China.The distribution of Theaceae species largely reflects the distribution characteristics of subtropical evergreen broad-leaved forest in China.Therefore,study the geographic distribution patterns of Theaceae plants have an important significance for understanding the distribution patterns and formation mechanisms of typical subtropical evergreen broad-leaved forest in China.Based on the comprehensive collection of Theaceae species distribution data and environmental factors,the geographic distribution patterns of Theaceae species and their influence factors on the national scale were analyzed by using species distribution modeling.The study also simulated the distribution patterns of Theaceae species,and then compared the spatial variations of suitable areas of Theaceae plants under current and future climatic conditions in China.In view of the above,we put forward corresponding conservation strategies.The main conclusions are as follows:(1)The distribution of Theaceae species diversity in China shows distinct latitudinal gradients.Species diversity decreases gradually from the south to the north.Fujian,Guangdong,Guangxi,Hainan and southern Guizhou have higher species richness of Theaceae.The distribution areas of Theaceae species in these provinces are in accordance with mountainous areas in southern China.The weighted endemism distribution patterns of Theaceae species are slightly different from the species richness patterns of Theaceae.High weighted endemism areas are distributed in all provinces of southern China,including Yunnan and Taiwan,which coincide with the south subtropical zone.The abundant hydrothermal condition in this climate zone promotes the diversity of Theaceae species,which verifies the tropical niche conservation hypothesis.The curve fitting of Theaceae species richness and weighted endemism identifies the endemism hotspots of Theaceae species.They are distributed in Yunnan,Hainan,Taiwan,southern parts of Guangdong and Guangxi.Protection measures should focus on these regions for their important representative significance.(2)The chosen environmental variables(climate factors and soil factors)in the study can well explain the geographic distribution patterns of Theaceae species in China.They can explain 78.9% of the variance in species richness,82.1% of the variance in species weighted endemism and 67% of the variance in relative residuals of weighted endemism respectively.Moreover,climate factors have higher individual interpretation rate than soil factors on the above three indicators.Among climate factors,energy have higher individual interpretation rate than water factors on the three indicators mentioned above.It means temperature is the dominant factor in explaining variations of spatial geographical distribution patterns of Theaceae species,especially annual mean temperature and temperature annual range.Warm and stable temperature is favorable to Theaceae speciation and differentiation,which indicates that Theaceae is a subtropical family.(3)Species diversity of Theaceae in China shows similar distribution patterns under eight climate change scenarios.With time going on and radiative forcing increasing,the distribution ranges of high species richness show varying reduction.We evaluate the changes in simulating distribution areas of Theaceae species under two extreme migration assumptions,and conclude that Theaceae species in Yunnan,Sichuan Basin,Taiwan and the Eastern Coastal areas are significantly affected by future climate change,which is performed in southeast and northeast of Yunnan,Taiwan,coastal areas of Fujian and Zhejiang,southern Sichuan Basin with higher emigrants.While the response of Theaceae in southwestern Yunnan,west and northeast of Sichuan Basin are moving in.Most of Theaceae species are kept in Guangdong,Guangxi,Guizhou and Hainan under changing climate,which may be due to the complex topography of mountainous in southern China.The montane areas can provide suitable habitats for most Theaceae species even in climate change scenarios.(4)Based on the response of Theaceae species to climate change,we propose the following protective strategies.For mountains with high species richness in southern China,more natural reserves are needed to protect and strengthen species migration in the vertical direction.For species distributed in flat areas,sustainable land use planning is of high importance for protection.Strengthen habitats management and improve the conservation consciousness of residents are also urgent for protecting Theaceae species.It is necessary to set up the botanical gardens and seed banks for special habitats,such as coastal areas,islands,limestone regions,which are sensitive to climate change.For species moving to high latitude,the main conservation measure is building corridors.For species with weak dispersal ability,other measures,such as artificial seeding,are necessary to assist migration.