title: Out of the blue: adaptive visual pigment evolution accompanies Amazon invasion.
abstract: Incursions of marine water into South America during the Miocene prompted colonization of freshwater habitats by ancestrally marine species and present a unique opportunity to study the molecular evolution of adaptations to varying environments. Freshwater and marine environments are distinct in both spectra and average intensities of available light. Here, we investigate the molecular evolution of rhodopsin, the photosensitive pigment in the eye that activates in response to light, in a clade of South American freshwater anchovies derived from a marine ancestral lineage. Using likelihood-based comparative sequence analyses, we found evidence for positive selection in the rhodopsin of freshwater anchovy lineages at sites known to be important for aspects of rhodopsin function such as spectral tuning. No evidence was found for positive selection in marine lineages, nor in three other genes not involved in vision. Our results suggest that an increased rate of rhodopsin evolution was driven by diversification into freshwater habitats, thereby constituting a rare example of molecular evolution mirroring large-scale palaeogeographic events.
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Ontario, Canada Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada.
authors.forename: Alexander
authors.initials: A
authors.lastname: Van Nynatten
authors.affiliation: Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, USA Environmental and Sustainability Studies Program, Western Michigan University, Kalamazoo, MI, USA.
authors.forename: Devin
authors.initials: D
authors.lastname: Bloom
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Ontario, Canada Department of Ecology and Evolutionary Biology, University of Toronto, Ontario, Canada Centre for the Analysis of Genome Evolution and Function, University of Toronto, Ontario, Canada belinda.chang@utoronto.ca.
authors.forename: Belinda S W
authors.initials: BS
authors.lastname: Chang
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Ontario, Canada Department of Ecology and Evolutionary Biology, University of Toronto, Ontario, Canada Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada lovejoy@utsc.utoronto.ca.
authors.forename: Nathan R
authors.initials: NR
authors.lastname: Lovejoy
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D059001:Aquatic Organisms; D017753:Ecosystem; D019143:Evolution, Molecular; D005399:Fishes / Q000235:genetics* / Q000502:physiology; D005618:Fresh Water; D016013:Likelihood Functions; D012243:Rhodopsin / Q000235:genetics*; D012623:Seawater; D013020:South America
chemical_list: D012243:Rhodopsin
keywords: South America; marine incursion; molecular evolution; rhodopsin; vision