Biodiversity underground

No, it's not a new political movement of Deep Ecology or anything. It's the discovery that there is a gradient of biodiversity in subterranean cave systems across the middle latitudes of the northern hemisphere. The authors consider that the Pleistocene epoch had something to do with it - glacial and other isolating factors caused a major increase in troglodyte speciation.

Figure: Map of species richness patterns of North American troglobionts. Major karst areas of eastern and central United States are shown in light gray. While there are many caves in the western United States and Canada, there are no large karst areas, and no areas of rich fauna. The open triangles are areas with few if any troglobionts, the gray triangle are areas with <50>2 of area or less. The black circle is the diversity hotspot in northeast Alabama. The boundary of the Pleistocene ice sheet is shown as a solid line. A pair of dashed lines indicates the hypothesized position of the high diversity ridge. B. Map of species richness patterns of European troglobionts. The open triangles are areas with few if any troglobionts, the gray triangles are areas with <50>2 of area or less. The black circles are the diversity hotspots in Slovenia and Ariege. Black triangles are other possible diversity hotspots. The boundary of the Pleistocene ice sheet is shown as a scored solid line. A pair of dashed lines indicates the hypothesized position of the high diversity ridge.