Cave Evolution

Abstract

Cave‐dwelling animals are fascinating because of the phenotypic extremes they frequently exhibit, such as a reduced or complete loss of vision and pigmentation. Equally interesting is the fact that irrespective of taxonomic position, organisms colonising the subterranean environment converge on highly similar phenotypic deficits and improvements. Thus, a predictable suite of morphological, physiological and behavioural changes evolve in response to low nutrient conditions of the subterranean environment. Despite several decades of enquiry, the precise genetic and molecular underpinnings of cave‐associated changes are only beginning to be elucidated through the use of high‐resolution contemporary molecular and genetic techniques. Regressive phenotypic changes, those traits that are lost in derived lineages, are particularly interesting since they evolve in the absence of obvious selective value to the organism. Continuing research utilising an increasing number of emerging cave‐dwelling models offers the exciting prospect of clarifying longstanding problems in contemporary evolutionary biology. Key Concepts: Widespread convergence on cave‐associated (troglomorphic) characteristics is often attributed to the paucity of nutrition and overall stability of the cave environment. Cave‐adapted organisms are excellent models for the study of regressive phenotypic evolution, that is the loss of traits in derived organisms. The evolutionary mechanism(s) accounting for phenotypic loss in cave‐dwelling organisms (neutralism versus selection) remains unknown. Hybrid crosses between cave‐dwelling and intra‐specific ‘surface’ forms reveal numerous morphological changes associated with cave adaptation are recessive. Phenotypic analyses in subsequent generations reveal many cave‐associated characteristics arise through Mendelian (single locus) and complex (polygenic) patterns of inheritance. The cave environment likely represents an attractive habitat given that over 50 000 cave‐limited species are known worldwide, distributed across broad taxonomic groups. Contemporary cave research has advanced significantly over the last decade thanks to integrative analyses combining developmental, genetic, genomic, behavioural, physiological and population‐level approaches.

Reproductive strategies of Moina (Cladocera) in relation to their habitat

“…However, species inhabiting temporary water bodies need to ensure the formation of resting stages and therefore should invest more in male and ephippial production than those that inhabit permanent waters (Dodson & Frey, 2010). Taxa living in temporary habitats with an uncertain supply of food resources should also be more resistant to starvation (Gross, 2012). Here, using three species of the same genus, Moina, we tested the hypothesis that species (M. cf.…”