Research On The Distribution Pattern And Conservation Of Crab Diversity In South Subtropical And Tropical Freshwater In China

The subtropical and tropical zones of China(SSTZ),starting from Fuzhou,Fujian in the north,reaching Hainan Island in the south,and starting from Ruili,Yunnan in the west,reaching Taiwan Island in the east,is one of the areas with extremely uneven economic development and one of the most concentrated areas of biodiversity hotspots in China.It has attracted wide attention from researchers.As a key group of freshwater benthic macroinvertebrates,freshwater crabs play an important role in maintaining the functional integrity of freshwater ecosystem.However,with the growth of human population and the advancement of urbanization,the changes of land use types and freshwater quality all pose a great ecological pressure on the habitats of freshwater crabs in the area.Therefore,understanding the diversity distribution of freshwater crabs in this area is a prerequisite for conducting diversity conservation researches and conservation actions for freshwater crabs.In this study,a distribution database of freshwater crab species in SSTZ was established by field investigation and systematic literature review.The species distribution modelling(SDM)was used to predict the potential distribution of freshwater crab species in this area,and further screen the environmental factors that have an important explanatory effect on the diversity of freshwater crabs in the region.In addition,potential distribution hotspots were identified.Considering the existing network of nature reserves,the conservation gaps based on overlap analysis and priority areas analysis based on multi-species were investigated.The main conclusions were as follows:(1)A total of 154 freshwater crab species,belonging to 37 genera and 2 families,were found in the subtropical and tropical regions of China,which cover 44% of the total species and 69% of the total genera in China.In this region,146 species and 31 genera were endemic to China,which cover 94% of total species and 84% of total genera respectively.(2)The areas with high species diversity are mainly located in the central and southern regions of Yunnan Province,the central and southern regions of Hainan Island,the Pearl River Delta of Guangdong Province to Hong Kong Special Administrative Region and the northern and southern regions of Taiwan Island;The diversity of freshwater crabs is mainly affected by altitude and temperature annual range.The relationship between freshwater crab species richness and land cover type indicates that there was a negative correlation between freshwater crab diversity and the proportion of land cover types affected by human activities,such as farmland,but a positive correlation between freshwater crab diversity and the proportion of land cover types,such as forest.(3)Ten hotspots are identified in SSTZ with significant aggregation distribution(Z=505.57;P < 0.05).Five of them are concentrated in Yunnan province,located in Laobie Mountains and Bangma Mountains in the west,Xishuangbanna Prefecture in the southwest,Ailao Mountains and Wuliang Mountains in the central area and Wenshan County-Maguan County-Malipo County in the south-central area;The other five hotspots are scattered in the Duyang Mountains-Hongshui River-Yujiang River in central and western Guangxi Province,the Pearl River Delta of Guangdong Province to the Hong Kong Special Administrative Region,the central and southern regions of Hainan Island,the southwestern region of Xueshan Mountain Range in the northern part of Taiwan Island and Yushan Mountain Range in the southern part of Taiwan Island.(4)Compared with the nature reserves,the “Priority Areas for Biodiversity Conservation” have higher coverage of freshwater crab hotspots in southern Yunnan and south-central Hainan.Integrating the coverage of hotspots by nature reserves and“Priority Areas for Biodiversity Conservation”,six major conservation gaps were identified.They are located in Yunnan,Guangxi,and Taiwan province.The three conservation gaps in Yunnan Province are located in Laobie Mountains and Bangma Mountains,Wuliang Mountains and Ailao Mountains and southern Ailao Mountains to the middle and lower reaches of Yuanjiang;The gaps in Guangxi Province is located in the Duyangshan Mountains–Hongshui River–Yujiang River in central and western Guangxi;Two gaps in Taiwan Province are located in the southwestern Xueshan Mountain Range and the southwestern Yushan Mountain Range.The analysis of priority areas based on multi-species shows that the existing nature reserves only cover an average of 11.16% of the distribution area of all 154 freshwater crabs;Raising the existing nature reserve to 15% of the total study area would increase its average coverage on the distribution area of freshwater crabs more than sixfold to 69%.In addition,for the conservation of freshwater crabs in this area,two specific suggestions were put forward: 1)strengthen the protection of river source;2)establish protected areas for the species with extremely small populations.In this study,the pattern of diversity,the distribution of hotspots and conservation gaps of freshwater crabs in the SSTZ were investigated,which can provide data support and scientific basis for the conservation management and decision-making of freshwater benthic macroinvertebrates in this region in the future.