Abstract
Adaptive radiation is the evolution of ecological and phenotypical diversity. It arises via ecological opportunity that promotes the exploration of underutilized or novel niches mediating specialization and reproductive isolation. The assumed precondition for rapid local adaptation is diversifying natural selection, but random genetic drift could also be a major driver of this process. We used 27 populations of European whitefish (Coregonus lavaretus) from nine lakes distributed in three neighboring subarctic watercourses in northern Fennoscandia as a model to test the importance of random drift versus diversifying natural selection for parallel evolution of adaptive phenotypic traits. We contrasted variation for two key adaptive phenotypic traits correlated with resource utilization of polymorphic fish; the number of gill rakers and the total length of fish, with the posterior distribution of neutral genetic differentiation from 13 microsatellite loci, to test whether the observed phenotypic divergence could be achieved by random genetic drift alone. Our results show that both traits have been under diversifying selection and that the evolution of these morphs has been driven by isolation through habitat adaptations. We conclude that diversifying selection acting on gill raker number and body size has played a significant role in the ongoing adaptive radiation of European whitefish morphs in this region.
Highlights
Adaptive radiation is a process where a lineage diversifies into new lineages adapted to divergent environments, which results in phenotype- environment associations, niche specialization, and genetic divergence (Gavrilets & Vose, 2005)
Natural selection acts as a driving force for rapid local adaptation (Barrett & Schluter, 2008), whereas random genetic drift, mutations, and gene flow may play a role in changing gene frequencies in populations
The results of our study show that phenotypic differentiation in the three whitefish morphs was a response to diversifying selection, as neutral drift- based divergence was not able to explain the observed pattern
Summary
Adaptive radiation is a process where a lineage diversifies into new lineages adapted to divergent environments, which results in phenotype- environment associations, niche specialization, and genetic divergence (Gavrilets & Vose, 2005). Natural selection acts as a driving force for rapid local adaptation (Barrett & Schluter, 2008), whereas random genetic drift, mutations, and gene flow may play a role in changing gene frequencies in populations Notwithstanding, nonadaptive processes, such as genetic linkage and pleiotropy of traits, may play important roles in the phenotypic and genotypic differentiation involved in adaptive radiations (Schluter, 2000). Divergence of populations, and eventually speciation, can occur via random genetic drift (Lee, Shaner, Lin, & Lin, 2016; Uyeda, Arnold, Hohenlohe, & Mead, 2009) Because of this complexity, the mechanisms by which evolution modulates phenotypic and genotypic frequencies in the divergence process are not well understood. Using the Bayesian methods implemented in “driftsel,” it is possible to contrast and statistically test differentiation of phenotypic traits under scenarios of random genetic drift and diversifying selection, and thereby compare possible similarities among phenotypes and environments (e.g., habitats) even with small number of populations or when QST equals FST (Ovaskainen et al, 2011)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
