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).