Chapter 6 - Adaptation and natural selection in caves

Abstract

Cave animals provide striking examples of evolution by natural selection, but relatively few studies examining the actual processes have been conducted so far. Natural selection seems mostly to be acting in a directional manner, increasing adaptation to the subterranean environment both through the elaboration and rudimentation of traits. Divergent selection between the surface and the cave environment is an important force-driving speciation of cave species in the presence of their surface ancestors. Divergent selection under ecological competition and adaptation to distinct micro-environments within caves could explain the differentiation of cave faunas in the process of subterranean adaptive radiation. Molecular clocks and mathematical models suggest that evolution of typical troglomorphic traits such as eye reduction can take place by strong selection even in the presence of gene flow from surface populations and within some 10,000years or less. However, some genomic and other recent studies still suggest that neutral mutation may play a role in the evolution of reduced troglomorphic traits, too.