| Popis: |
Poster at SMBE 2015 in Vienna, Austria Abstract Understanding of the mechanisms by which populations diverge and become species are in their infancy, especially when those populations are in sympatry. We present a genome-wide SNP data set obtained using a RAD-sequencing approach to identify the regions of the genome which may be involved in the divergence and isolation of four Lake Malawi Diplotaxodon species. These deep water species have been previously proposed as examples of sympatric speciation, differing to some extent in morphology, and more obviously in male monochromatic nuptial colour. Principal component analysis and Discriminant analysis of principal components on >20,000 SNPs support significant genetic differentiation between the four species. We apply and compare Fst outlier scan approaches to detect signals of divergent selection. Based on the intersection of three independent approaches we infer a conservative set of outlier candidate regions, i.e. putative ‘genomic islands of speciation’. Gene ontology enrichment analyses of the functional classes of genes in these regions strongly support the hypothesis that the machinery of transcriptional regulation plays a central role in the differentiation of these species. We furthermore infer previously identified differences in head morphological traits between species to be significantly correlated with allele frequencies in candidate regions enriched for genes controlling craniofacial- and eye development. Our results indicate that the increasingly narrow, short wave-length light-spectra at greater water depths appear to pose unique selective constraints and are likely key drivers of ecological and sexual selection and ultimately speciation in this group of Lake Malawi cichlids. |
