Fig. 3.

Distribution of the snail records in the Yangtze River Basin with increasing cell sizes. a Snail records according to the 2018 field survey; b–f Spatial correction using 5, 10, 50, 100 and 150 km distance between the centres of adjacent cells, respectively. Snail records (with red for presence and blue for absence) adjusted to keep 1 or two records per grid cell. Note that cells are not shown for Figures a–c since the sizes would have been too small at those scales