engleski

Phenotypic plasticity as a mechanism of cave colonization and adaptation

A widely accepted model for the evolution of cave animals posits cave colonization by surface dwelling ancestors followed by the acquisition of adaptive traits over many generations. However, the speed of cave adaptation in some species is difficult to reconcile with this conventional viewpoint, suggesting the importance of alternative mechanisms operating over shorter timescales. To address these mechanisms, we used Astyanax mexicanus, a teleost with multiple populations of conspecific cave-dwelling morphs (cavefish, CF) and an ancestral-like surface dwelling morph (surface fish, SF). We exposed SF to completely dark (dark/dark = D/D) conditions during early development and compared them to siblings placed on a standard photoperiod (light/dark = L/D). Numerous altered traits were identified in D/D SF compared to L/D SF at both the gene expression and phenotypic levels, including changes related to endocrine signaling, circadian rhythms, metabolism (especially in lipids), eye anatomy, pigmentation, metabolic rates, starvation resistance, and neurotransmitter levels. Remarkably, most of these alterations mimicked CF phenotypes. Our results indicate that many cave- related traits can be induced by darkness, the main feature of subterranean habitats, and can appear within a single generation by phenotypic plasticity. In the next generation, plasticity can be enhanced and traits further refined. The initial plastic responses are random in adaptive outcome but may determine the subsequent course of adaptive evolution. Our study suggests that phenotypic plasticity contributes to the rapid evolution of cave- related traits, enabling a successful transition of A. mexicanus to dark cave habitats. Future studies using Dinaric cave fauna will address whether plasticity is a general phenomenon in the colonization and adaptation to cave environments.

adaptation ; environmental change ; cave-adapted animal

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