Ecology and Genetics of Phenotypic Integration and the Role for Adaptation in Threespine Stickleback
Date
2019-07-09
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Abstract
Determining the underlying causes for the links between form, function, and the environment, and how these correlations relate to adaptation to novel environments represent integral problems in evolutionary biology. While investigations have been conducted on adaptive divergence involving single, isolated traits, adaptation is multifaceted, requiring the examination of complex, multidimensional phenotypes. In this thesis, I evaluated the hypothesis that phenotypic covariation and phenotypic integration are linked to genetic covariation and facilitate adaptation to novel environments. Phenotypic variation and covariation, along with genetic differentiation between multiple wild stickleback subpopulations and laboratory reared groups were described using three dimensional geometric morphometric data from stickleback skeletal structures as well as genomic information from high density Single Nucleotide Polymorphisms (SNPs; sensu Pool-Seq). I evaluated whether divergence in putatively adaptive traits was higher than expected under expectations for neutral evolution via PST-FST comparisons of phenotypic covariation and contrasted patterns of genetic and phenotypic variation. I determined the genetic basis of phenotypic integration using a controlled common garden experiment and investigated the genetic architecture of integrated skeletal structures through Quantitative Trait Locus (QTL) analysis carried out on linkage maps that I generated from SNPs characterized by double restriction digest reduced representation sequencing (ddRAD-Seq). Finally, I evaluated whether this genetic architecture was being maintained by selection in wild populations by testing the hypothesis that molecular divergence was higher than expected at genetic regions associated with phenotypic traits. I found the amount of phenotypic variation and strength of integration varies across the stickleback skeleton as well as among marine populations and that directional selection is acting on phenotypic integration in all observed populations. I determined that phenotypic integration across the skeleton is controlled by genetic factors, though there is a strong effect of environment on trophic traits. Finally, I characterized 33 significant QTL linked to integrated skeletal traits, finding 2702 SNP outliers within the identified QTL under selection between marine and freshwater environments. Collectively, my thesis highlights integration as an essential component of adaptive divergence and as one of the potential driving forces for the rapid adaptation of populations to novel environments.
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Keywords
Threespine Stickleback, Variation, Covariation, Integration, Selection, Adaptation
Citation
Barry, T. N. (2019). Ecology and Genetics of Phenotypic Integration and the Role for Adaptation in Threespine Stickleback (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.