Genetic analysis of cavefish reveals molecular convergence in the evolution of albinism

Abstract

The genetic basis of vertebrate morphological evolution has traditionally been very difficult to examine in naturally occurring populations. Here we describe the generation of a genome-wide linkage map to allow quantitative trait analysis of evolutionarily derived morphologies in the Mexican cave tetra, a species that has, in a series of independent caves, repeatedly evolved specialized characteristics adapted to a unique and well-studied ecological environment. We focused on the trait of albinism and discovered that it is linked to Oca2, a known pigmentation gene, in two cave populations. We found different deletions in Oca2 in each population and, using a cell-based assay, showed that both cause loss of function of the corresponding protein, OCA2. Thus, the two cave populations evolved albinism independently, through similar mutational events.

Introgression and repeated co-option facilitated the recurrent emergence of C4photosynthesis among close relatives

“…The use of distinct components can be interpreted as evidence for multiple origins, while reversals could leave a signature of the lost trait that can be detected when components are compared with those from species that never evolved it (Protas et al. 2006; Christin et al. 2010; Oliver et al.…”

Evolution: Biology's next top model?

“…Still, several populations have converged on this phenotype. Contrast that to albinism, which has happened in almost the same way in various cave-fish population, via a mutation to the OCA2 gene 4 . This gene makes a protein crucial to development of pigmented 'melanocytes' and happens to be the most commonly mutated gene in human albinism.…”

Distinct Evolutionary Patterns Between Two Duplicated Color Vision Genes Within Cyprinid Fishes

“…Many of these troglomorphic fishes show striking adaptation to this kind of extremely rigorous environment and are often characterized by a remarkable convergence of eye and pigmentation reduction or loss (Protas et al 2006). Sinocyclocheilus (Cypriniformes, Cyprinidae), is the most cavefish-rich genus, with about 20 of its *50 species being cave dwellers (Zhao and Zhang 2006).…”