Faculty of Biology of the University of Constance
Department of Biology
Laboratory for Zoology and Evolutionary Biology
Building M, Floor 8, Room 825
Abstracts (first author)
Genomic instability in the locus responsible for a conspicuous polychromatism in Nicaraguan Midas Cichlid FishPDF
Body coloration is polymorphic in many species. It is subject to both natural selection (e.g. cryptic coloration) and sexual selection (e.g. male nuptial coloration). Two extraordinary features of Cichlids are their enormous diversity in coloration and their rapid rates of diversification. Sexual selection on coloration has been proposed to be one of the major forces driving their explosive speciation rates, which makes them an ideal system to study the effects of body coloration on speciation processes. Most of the Nicaraguan lakes are inhabited by two color morphs of Midas cichlids: a barred dark morph, which represents the majority of individuals (~90%), and a gold morph (7 - 10%). All individuals have the normal phenotype at early stages of their life but some lose their dark coloration and become gold. Gold and normal fish mate assortatively and genetic divergence of neutral markers occurs between the two morphs. All of which suggests a role of this trait in the process of incipient speciation. In this study, we characterize the architecture of the genomic region that harbors the causal gold polymorphism. The interval was reduced to approximately 60 kb and it, as well as the flanking regions, shows strong evidence of genomic instability. This includes several indels of various sizes, gene duplications and chromosomal rearrangements. Lineage-specific, tandemly duplicated genes have been identified, some of which show signs of pseudogenization and selection. Comparative genomic analysis of the region indicates the presence of cichlid-specific and perhaps even Midas-specific chromosomal rearrangements. Regions of genomic instability have been proposed to have an impact on speciation due to altered recombination and mutation rates. The present study illustrates the architecture of an unstable genomic region that might underlie incipient sympatric speciation in Nicaraguan Midas cichlids.