US Counties and Amphibians
Within the USA, county boundaries were primarily used, with only 2% of
the area over 500m from county borders containing amphibian range
limits, whereas 20% of county boundaries have >10
amphibian species range boundaries recorded, and only 31% of all US
county borders do not show overlap (Figure S2a). Almost 60% of
amphibian species in the US had all their range boundaries on county
borders, and the 40% that show some of their ranges off county borders
include invasive alien species like Xenopus laevis . In addition,
many of these species were range-restricted, with 20% showing a range
<100km2, 6%
<10km2 and 3%
<1km2. Notably, similarly low-level
administrative areas were not used in other regions.