RESEARCH ARTICLE Phenotypic plasticity as a mechanism of cave colonization and adaptation Helena Bilandzˇija1,2, Breanna Hollifield1, Mireille Steck3, Guanliang Meng4,5, Mandy Ng1, Andrew D Koch6, Romana Gracˇan7, Helena C´ etkovic´ 2, Megan L Porter3, Kenneth J Renner6, William Jeffery1* 1Department of Biology, University of Maryland, College Park, United States; 2Department of Molecular Biology, Ruđer Bosˇkovic´ Institute, Zagreb, Croatia; 3Department of Biology, University of Hawai’i at Manoa, Honolulu, United States; 4BGI-Shenzhen, Shenzhen, China; 5China National GeneBank, BGI-Shenzhen, Shenzhen, China; 6Department of Biology, University of South Dakota, Vermillion, United States; 7Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia 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. *For correspondence:
[email protected] Competing interests: The Introduction authors declare that no A major problem in modern biology is understanding how organisms adapt to an environmental competing interests exist.