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Directional selection is the primary cause of phenotypic diversification
Loren H Rieseberg1, Alex Widmer, A Michele Arntz
1Department of Biology, Indiana University, Bloomington, IN 47405-3700, USA. lriesebe@indiana.edu
Summary
Directional selection drives phenotypic diversification and speciation, validating Darwin's theory. Analysis of quantitative trait loci (QTLs) across many studies shows selection is a primary evolutionary force.
Area of Science:
- Evolutionary Biology
- Genetics
- Speciation Research
Background:
- Phenotypic variation is key to evolution, but selection's role in speciation is debated.
- Nonadaptive differences between species challenge the primacy of selection in macroevolution.
Purpose of the Study:
- To assess the role of directional selection in phenotypic divergence using a quantitative trait locus (QTL) sign test.
- To empirically validate Charles Darwin's assertion that selection drives phenotypic diversification.
Main Methods:
- Utilized the QTL sign test on 572 traits from 86 independent studies.
- Analyzed the directionality of QTL effects to infer historical selection pressures.
Main Results:
- Found significantly fewer antagonistic QTLs than expected under neutral evolution, supporting directional selection.
- Interspecific trait differences showed stronger or more consistent selection than intraspecific differences.
- Life history traits were more strongly selected than morphological traits; developmental timing traits were weakly selected.
Conclusions:
- Directional selection is the predominant force in phenotypic diversification and speciation.
- Empirical evidence supports Darwin's theory on selection's role in shaping biodiversity.
- Selection patterns differ between contemporary and evolutionary contexts, with life history traits being highly significant.