Repeated colonization of caves leads to phenotypic convergence in catfishes (Siluriformes: Trichomycterus) at a small geographical scale

Across various animal groups, adaptation to the challenging conditions of cave environments has resulted in convergent evolution. We document a Neotropical cavefish system with ample potential to study questions related to convergent adaptation to cave environments at the population level. In the karstic region of the Andes of Santander, Colombia, cave-dwelling catfish in the genus Trichomycterus exhibit variable levels of reduction of eyes and body pigmentation relative to surface congeners. We tested whether cave-dwelling, eye-reduced, depigmented Trichomycterus from separate caves in Santander were the result of a single event of cave colonization and subsequent dispersal, or of multiple colonizations to caves by surface ancestors followed by phenotypic convergence. Using mitochondrial DNA sequences to reconstruct phylogenetic relationships, we found that caves in this region have been colonized independently by two separate clades. Additional events of cave colonization - and possibly recolonization of surface streams - may have occurred in one of the clades, where surface and cave-dwelling populations exhibit shallow differentiation, suggesting recent divergence or divergence with gene flow. We also identify potentially undescribed species and likely problems with the circumscription of named taxa. The system appears promising for studies on a wide range of ecological and evolutionary questions.

Automated summary

In the karstic region of the Andes of Santander, cave-dwelling catfish in the genus Trichomycterus exhibit variable levels of reduction of eyes and body pigmentation, which provides ample potential to study questions related to convergent adaptation to cave environments. The mitochondrial DNA sequences suggest that caves in this region have been colonized independently by two separate clades, with possible additional events of cave colonization in one clade. This system is promising for studies on a wide range of ecological and evolutionary questions.