Colonization and Speciation in Subterranean Environments

Abstract

Colonization and speciation in subterranean environments can be conveniently divided into four stages. The first step is colonization of subsurface environments. There is a constant flux of colonists into most subterranean habitats. The second step is the success (or failure) of these colonizations. The third step is speciation. Under the Climate Relict Hypothesis (CRH) surface populations go extinct but under the Adaptive Shift Hypothesis (ASH) they do not necessarily do so, and speciation can be parapatric. There is strong evidence for the CRH among temperate zone fauna, and growing evidence for the ASH in tropical caves, especially lava tubes. The final step is possible further speciation as a result of subsurface dispersal. Detailed analysis of the evolutionary history of the isopod A. aquaticus in the Dinaric karst, diving beetles Paroster in a calcrete aquifer in Western Australia, and trogloxenic Leopoldamys neilli in Thailand reveal some of the complexities of species’ phylogeography.