Structure and Genetics of Cave Populations

Abstract

Cave populations have been traditionally perceived as genetically strongly structured and less diverse than related surface populations because of the patchiness of subterranean habitats, low dispersal of cave species, and genetic bottlenecks at colonization. These patterns are at odds with relatively large and/or disjunct ranges of many troglobionts, as well as the countless successful cave colonizations. One way to disentangle those discrepancies is to discriminate between exogenous processes that take place at the surface or during invasion, and endogenous ones that take place in and are governed by the specific conditions of caves. Genetic evidence collected over the past decades suggests that ongoing endogenous processes, endogenous vicariance, and gene flow between allopatric cave populations have less effect on the genetic structure of cave populations than patterns inherited from past exogenous events. Conversely, most known cases of recent migration between non-neighboring cave populations entail the possibility of dispersal via the surface. Gene pools of young cave populations often show strong exogenous imprints such as multiple colonization events and/or recurring gene flow from the surface. This is compatible with the high propagule pressure hypothesis of successful biological invasions, while convincing molecular evidence for the genetic bottleneck hypothesis of cave colonization is sparse.