Evolutionary Genetics of Cavefish and Adaptation Mechanisms

The Mexican tetra and other cave‐dwelling teleosts have emerged as models to investigate the genetic basis of adaptation to perpetual darkness and resource limitation. Comparative genomic and transcriptomic analyses of cavefish and their surface‐dwelling conspecifics have revealed the interplay between natural selection, genetic drift and pleiotropy in shaping regressive traits such as eye and pigment loss, and constructive traits including sensory enhancement and metabolic adjustments. Repeated independent colonisations of subterranean habitats by surface ancestors have produced convergent phenotypes underpinned by parallel and unique genetic changes, implicating genes with large mutational targets and standing variation in rapid adaptation. High‐resolution genome assemblies and functional assays have identified key loci governing eye reduction, melanin synthesis, circadian rhythm modifications and behavioural shifts such as vibration attraction. Population‐level sequencing has illuminated the timing of cave invasions, gene flow between cave and surface forms, and the demographic parameters that influence fixation of adaptive alleles. Integrating quantitative trait locus mapping, CRISPR gene editing and ecological studies has advanced our understanding of how constraint and determinism guide evolutionary trajectories in extreme environments, informing broader questions of phenotypic convergence, developmental plasticity and potential biomedical applications of naturally evolved mutants.

Research from Nature Portfolio

Recent studies using whole‐genome resequencing of the Mexican tetra have demonstrated that both standing genetic variation and de novo mutations contribute substantially to parallel losses and enhancements of traits across independent cavefish lineages. These analyses have shown that genes with larger mutational targets are preferential substrates for repeated adaptation and highlighted environmental factors in caves that may influence mutation rates. In addition, the release of a chromosome‐level genome assembly for surface fish has enabled comprehensive genome‐wide comparisons with cave populations, leading to the identification of novel candidate genes within eye‐size quantitative trait loci and validated by functional assays such as CRISPR. This resource has also facilitated the first genome‐wide survey of structural variation across cavefish populations, uncovering deletion patterns that may underpin troglomorphic phenotypes.

Evolutionary Genetics of Cavefish and Adaptation Mechanisms publication trend

The graph below shows the total number of articles in evolutionary genetics of cavefish and adaptation mechanisms across all publications each year (not limited to Nature Index journals).

Technical terms

standing genetic variation: Pre‐existing allelic diversity within a population that can be acted on by selection during environmental change.

de novo mutation: A novel genetic alteration that arises spontaneously rather than being inherited.

quantitative trait locus (QTL): A chromosomal region containing genes that contribute to variation in a measurable trait.

parallel evolution: Independent evolution of similar traits in different populations due to similar selective pressures.

troglomorphic traits: Morphological and behavioural adaptations characteristic of cave‐dwelling organisms, such as eye and pigment reduction.

References

1. Selection-driven trait loss in independently evolved cavefish populations. Nature Communications (2023).
2. The Mexican Tetra, Astyanax mexicanus, as a Model System in Cell and Developmental Biology. Annual Review of Cell and Developmental Biology (2023).
3. Evidence for late Pleistocene origin of Astyanax mexicanus cavefish. BMC Ecology and Evolution (2018).
4. Gene flow and population structure in the Mexican blind cavefish complex (Astyanax mexicanus). BMC Ecology and Evolution (2012).
5. The complex origin of Astyanax cavefish. BMC Ecology and Evolution (2012).
6. A Novel Role for Mc1r in the Parallel Evolution of Depigmentation in Independent Populations of the Cavefish Astyanax mexicanus. PLOS Genetics (2009).
7. Eyeless Mexican Cavefish Save Energy by Eliminating the Circadian Rhythm in Metabolism. PLOS ONE (2014).
8. Evolution of an adaptive behavior and its sensory receptors promotes eye regression in blind cavefish. BMC Biology (2012).
9. Evolution of eye development in the darkness of caves: adaptation, drift, or both?. EvoDevo (2013).
10. A chromosome-level genome of Astyanax mexicanus surface fish for comparing population-specific genetic differences contributing to trait evolution. Nature Communications (2021).