From Cave Dragons to Genomics: Advancements in the Study of Subterranean Tetrapods

Throughout most of the kingdom Animalia, evolutionary transitions from surface life to a life permanently bound to caves and other subterranean habitats have occurred innumerous times. Not so in tetrapods, where a mere 14 cave-obligate species-all plethodontid and proteid salamanders-are known. We discuss why cave tetrapods are so exceptional and why only salamanders have made the transition. Their evolution follows predictable and convergent, albeit independent pathways. Among the many known changes associated with transitions to subterranean life, eye degeneration, starvation resistance, and longevity are especially relevant to human biomedical research. Recently, sequences of salamander genomes have become available opening up genomic research for cave tetrapods. We discuss new genomic methods that can spur our understanding of the evolutionary mechanisms behind convergent phenotypic change, the relative roles of selective and neutral evolution, cryptic species diversity, and data relevant for conservation such as effective population size and demography.

Automated summary

Evolutionary transitions to cave life have occurred numerous times in most of the Animalia kingdom, but only 14 cave-obligate species of tetrapods, all salamanders, are known. Salamanders' transition to caves follows predictable and convergent, albeit independent pathways, with characteristics such as eye degeneration, starvation resistance, and longevity being relevant for human biomedical research. Genomic research on cave tetrapods has recently become available, providing insights into evolutionary mechanisms, neutral evolution, cryptic species diversity, and conservation data.