Historical and Ecological Factors Determining Cave Diversity

Abstract

Species living in the deep subterranean environment tend to share similar morphological characters evolved independently from epigean ancestors, the troglomorphic phenotype. They also tend to have very restricted distributions, as a consequence of their limited dispersal capabilities. Until recent years, the predominant view on the evolution of the subterranean fauna was that troglomorphic species were strictly confined to the deep subterranean environment, with the implication that species not in close geographic vicinity must have independently developed their troglomorphic characters in a sort of concerted evolution close to the traditional concept of orthogenesis. Recent developments on the knowledge of the ecology and the phylogenetic history of several groups with abundance of subterranean species are changing this view. First, there is increasing evidence that epigean and deep subterranean environments form a continuum without clear limits and that troglomorphic species can occupy different parts of this continuum at different times depending on their particular conditions. And second, the availability of molecular phylogenies has led to the discovery of monophyletic lineages of troglomorphic species only, suggesting the single origin of the subterranean colonisation and of the troglomorphic characters, with subsequent dispersal and diversification of already subterranean species.