Genetic mapping of the Midas cichlid GOLD locus

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The question of how new species arise has been at the centre of evolutionary biological research ever since Darwin. Despite widespread interest in the genetics of speciation, only a handful of genes that contribute to species isolation have been discovered so far. Cichlid fishes have the fastest known rate of speciation and therefore are well-suited model organisms for the study of speciation. The Midas cichlids of Central America were recently shown to have diverged in the absence of geographic isolation through ecological specialization and by colour-based assortative mating. Several species come in two colour morphs: normal (also called "barred" or "dark") and "gold". Gold and nornial fish choose mates based on colour and very strongly prefer mates of their own colour over individuals with a different colouration. However, virtually nothing is known about the genetic basis of the colour differences and especially, the mating preference for colour. Knowledge about the genetic bases of these important phenotypic differences is crucial for a deeper understanding of how this difference in colouration has evolved and how it promotes speciation. The cause of pigmentation differences in these fish will also provide insights into the genetics of human pigmentation disorders since all fish start out as "dark" morphs and only the genetically gold individuals lose their melanophores later in life. Previous results from my laboratory show that the gold phenotype is dominant and is likely due to a single gene. We have mapped it already to a genomic region that contains only about 10 to 15 genes. Taking advantage of recent technological and methodological developments, this project aims to positionally fine-map,p identify and functionally validate the gene/mutation(s) responsible for the gold colour in the Midas cichlid - a gene that is involved in the origin of new species.