Natural selection hampers divergence of reproductive traits in a seed beetle

Authors

  • C. FRICKE,

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    • 1

      Present address: Centre for Ecology, Evolution and Conservation, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.

  • C. ANDERSSON,

    1. Evolutionary Biology Centre, Department of Ecology and Evolution, Animal Ecology, Uppsala University, Norbyvägen 18D, Uppsala, Sweden
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  • G. ARNQVIST

    1. Evolutionary Biology Centre, Department of Ecology and Evolution, Animal Ecology, Uppsala University, Norbyvägen 18D, Uppsala, Sweden
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Claudia Fricke, Evolutionary Biology Centre, Department of Ecology and Evolution, Animal Ecology, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden. Tel.: ++(0)1603 592 947; Fax: ++(0)1603 592 250; e-mail: C.Fricke@uea.ac.uk

Abstract

Speciation is thought to often result from indirect selection for reproductive isolation. This will occur when reproductive traits that cause reproductive isolation evolve (i) as a by-product of natural selection on traits with which they are genetically correlated or (ii) as an indirect result of diversifying sexual selection. Here, we use experimental evolution to study the degree of divergent evolution of reproductive traits by manipulating the intensity of natural and sexual selection in replicated selection lines of seed beetles. Following 40 generations of selection, we assayed the degree of divergent evolution of reproductive traits between replicate selection lines experiencing the same selection regime. The evolution of reproductive traits was significantly divergent across selection lines within treatments. The evolution of reproductive traits was both slower and, more importantly, significantly less divergent among lines experiencing stronger directional natural selection. This suggests that reproductive traits did not evolve as an indirect by-product of adaptation. We discuss several ways in which natural selection may hamper divergent evolution among allopatric populations.

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