Species turnover on the boundaries
When species ERM boundaries are aggregated to show the number of range
boundaries which overlap (Figure S1), and then reclassified to show only
areas with the most overlapping species range boundaries, it becomes
apparent that the hotspots of where species boundaries are delineated
fall on national administrative borders. Within 500m of national
borders, 30-50% of the top two richness classes, and 35-50% of the top
three richness classes are included. This increases to between 43-65%
for top-two at 1km, and 51-70% of top-three, and >80%
within 5km, indicating species range boundaries are frequently delimited
at administrative borders, though with varying precision (Table 2).