DISTRIBUTION MODELS AND CONSERVATION REQUIREMENTS OF FRESHWATER MOLLUSCA IN THE YANGTZE RIVER BASIN

This study selected three taxonomy groups (Prosobranchia, Pulmonata and Bivalvia) of freshwater Mollusca as the conservation target to build MaxEnt distribution models and analyze relevant conservation requirements based on field investigations and literature collections of species data and environments. The results showed that: (1) Bioclimatic variables were the key groups of environments to explain the distribution variance of the three taxonomy groups. Human disturbance variables also played an important role. Elevation and upstream were the two important factors for distributions of Probsobranchia and Bivalvia, while weakly related to that of Pulmonata. (2) Cumulative species-area (length) relationships were established, according to which the minimum requirements of the length of mainstem and tributaries, the area of river-isolated and -connected lakes were 1181 km, 16960 km, 6397 km², and 5609 km², respectively. They accounted for 18.7%, 8.7%, 70.6%, and 86.3% of the total length of mainstem, the total length of tributaries, the total area of river-isolated lakes and the total area of river-connected lakes in the Yangtze River Basin, respectively. 3) The main distribution areas of freshwater Mollusca are Lake Poyanghu, Lake Dongtinghu, Lake Taihu, and the mid-lower mainstem of the Yangtze River. The established freshwater ecosystems reserves (2.1×10⁴ km²) and rivers (1885 km) were found insufficient and scattered. They overlapped little with the predicted distribution areas. The results provide reasonable advices for biodiversity conservation of freshwater Mollusca and also systematic conservation of the Yangtze River Basin on the whole-basin scale.