Phenotypic plasticity as a mechanism of cave colonization and adaptation

Abstract

A widely accepted model for the evolution of cave animals posits colonization by surface ancestors followed by the acquisition of adaptations over many generations. However, the speed of cave adaptation in some species suggests mechanisms operating over shorter timescales. To address these mechanisms, we used Astyanax mexicanus, a teleost with ancestral surface morphs (surface fish, SF) and derived cave morphs (cavefish, CF). We exposed SF to completely dark conditions and identified numerous altered traits at both the gene expression and phenotypic levels. Remarkably, most of these alterations mimicked CF phenotypes. Our results indicate that many cave-related traits can appear within a single generation by phenotypic plasticity. In the next generation, plasticity can be further refined. The initial plastic responses are random in adaptive outcome but may determine the subsequent course of evolution. Our study suggests that phenotypic plasticity contributes to the rapid evolution of cave-related traits in A. mexicanus.

Comparative Transcriptomics Reveals the Molecular Genetic Basis of Cave Adaptability in Sinocyclocheilus Fish Species

“…We believe that dietary preferences may cause differences in energy intake, ultimately affecting blood glucose regulation. Furthermore, these results may confirm the previous hypothesis that starvation resistance and metabolic regulation of cavefish would be present in multiple independently evolved cavefish populations (Bilandžija et al, 2020). However, more in-depth studies involving quantitative detection of insulin and blood glucose in the Sinocyclocheilus cave and surface fish species is still needed to verify the relationship between these DEGs and cave adaptability.…”

Thermal Plasticity in Insects’ Response to Climate Change and to Multifactorial Environments

“…Plasticity can be targeted by selection and evolve, and can, in turn, impact adaptive evolution (reviewed in Lafuente and Beldade, 2019). It has been argued that developmental plasticity can help (or hinder; e.g., Cenzer, 2017;Oostra et al, 2018) not only the immediate survival, but also future adaptation of populations facing environmental perturbation (Reed et al, 2011;Bonamour et al, 2019) and colonizing novel environments (Ghalambor et al, 2007;Wang and Althoff, 2019;Bilandžija et al, 2020). In addition, it has been proposed that plasticity can promote phenotypic and taxonomic diversification (Moczek, 2010;Pfennig et al, 2010;Schneider and Meyer, 2017).…”

Astyanax surface and cave fish morphs

“…The relationship between traits expressed in the laboratory and field [43], interactions between cavefish and other cave fauna, including trophic interactions and parasitism, and the physical differences in cave ecosystems leading to adaptation are ripe for investigation. How surface fish first colonized the challenging cave environment, including the roles of standing and cryptic genetic diversity [44], phenotypic plasticity and genetic assimilation [45], and adaptive and neutral evolution [46], are also worthwhile pursuits. Limitations for ecological studies are related to the remoteness of the caves, the difficulties in studying cave habitats, and severe and dangerous cave flooding.…”