Abstracts (first author)
The genetic bases of body shape architecture of two sympatric Mesoamerican cichlid species: a RAD-QTL approach
Determining the genetic bases of phenotypic adaptation and ultimately speciation is one of the major quests in evolutionary biology. Cichlid fish species flocks are a prime example of recent rapid radiations often associated with adaptive phenotypic divergence from a common ancestor in a short period of time. In these fishes divergence in eco-morphological traits, including body shape, colour, lips and jaws, are thought to underpin their diversification. The Midas cichlid species complex (Amphilophus) of Nicaragua provides one of the few known examples of sympatric speciation, where species have rapidly evolved different eco-morphologies in young crater lakes. In this study we use SNP marker genotypes generated using ddRAD sequencing and a combination of morphometric analyses to identify significant QTLs in ecologically divergent cichlid species with different body morphs: an elongated limnetic species (A. zaliosus) and a high-bodied benthic species (A. astorquii) inhabiting lake Apoyo. A total of 453 informative RAD markers were identified in 240 F2 hybrids. These markers were used to construct a genetic map for which 25 linkage groups were resolved. We found 27 segregating SNPs linked to QTLs. The QTL-linked genomic regions were annotated to identify genes that likely contribute to divergence in body shape in benthic and limnetic Midas cichlid sympatric species. These results underline the effectiveness of RAD-Seq as a tool for rapid and efficient generation of QTL-targeted and genome-wide marker data and a promising method for investigating the genomic bases of divergence in ecologically relevant traits.
A resampling-based approach to study variation in morphological modularityPDF
Modularity has been suggested to be connected to evolvability because an higher degree of independence among parts allows them to evolve as separate units. Recently, the Escoufier RV coefficient has been proposed as a measure of morphological modularity in multivariate morphometric datasets. However, it has been shown, using randomly simulated datasets, that the value of the RV coefficient depends on sample size. Also, so far there is no statistical test for the difference in modularity between a priori defined groups. Here we: 1. using a rarefaction analysis, show that the value of the RV Escoufier coefficient depends on sample size also in real morphometric datasets; 2. propose a permutation procedure to test for the difference in the RV coefficient between a priori defined groups; 3. show, through simulations, that such a permutation procedure has an appropriate Type I error. The permutation procedure outlined here, readily extendable to non-morphometric datasets, will allow statistically sound comparisons of the degree of modularity between a priori defined groups.