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Inter-locus antagonistic coevolution as an engine of speciation: assessment with hemiclonal analysis
Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara.
Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara.
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2005 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 102, no Suppl. 1, 6527-6534 p.Article in journal (Refereed) Published
Abstract [en]

One of Ernst Mayr's legacies is the consensus that the allopatry model is the predominant mode of speciation in most sexually reproducing lineages. In this model, reproductive isolation develops as a pleiotropic byproduct of the genetic divergence that develops among physically isolated populations. Presently, there is no consensus concerning which, if any, evolutionary process is primarily responsible for driving the specific genetic divergence that leads to reproductive isolation. Here, we focus on the hypothesis that inter-locus antagonistic coevolution drives rapid genetic divergence among allopatric populations and thereby acts as an important “engine” of speciation. We assert that only data from studies of experimental evolution, rather than descriptive patterns of molecular evolution, can provide definitive evidence for this hypothesis. We describe and use an experimental approach, called hemiclonal analysis, that can be used in theDrosophila melanogaster laboratory model system to simultaneously screen nearly the entire genome for both standing genetic variation within a population and the net-selection gradient acting on the variation. Hemiclonal analysis has four stages: (i) creation of a laboratory “island population”; (ii) cytogenetic cloning of nearly genome-wide haplotypes to construct hemiclones; (iii) measurement of additive genetic variation among hemiclones; and (iv) measurement of the selection gradient acting on phenotypic variation among hemiclones. We apply hemiclonal analysis to test the hypothesis that there is ongoing antagonistic coevolution between the sexes in the D. melanogaster laboratory model system and then discuss the relevance of this analysis to natural systems.

Place, publisher, year, edition, pages
Washington: National Academy of Sciences , 2005. Vol. 102, no Suppl. 1, 6527-6534 p.
Keyword [en]
sexual conflict, inter-locus contest evolution, sexually antagonistic coevolution, reproductive isolation, genetic divergence
URN: urn:nbn:se:umu:diva-5015DOI: 10.1073/pnas.0501889102OAI: diva2:144358
Available from: 2006-03-30 Created: 2006-03-30 Last updated: 2011-03-21Bibliographically approved
In thesis
1. Sexual conflict and male-female coevolution in the fruit fly
Open this publication in new window or tab >>Sexual conflict and male-female coevolution in the fruit fly
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Harmony and cooperation was for long believed to dominate sexual interactions. This view slowly started to change 25 years ago and is today replaced with a view where males and females act based on what is best from a costs-benefits perspective. When sex specific costs and benefits differ, concerning reproductive decision influenced by both sexes, sexual conflict will occur. The basis for discordant reproductive interests between the sexes is that males produce many small gametes, while females’ produce few and large gametes. One result of this difference is that the optimal mating rate differs between the sexes. Males, with their many small sperm, maximize their reproductive output by mating with many females, while females often do best by not mating more frequently than to fertilize their eggs, since mating often entails a cost. Sexual conflict over mating is thus an important factor shaping the interactions between the sexes. In this thesis I study this and related conflicts between the sexes, using mathematical models, fruit flies and comparative methods. Mathematical modelling was used to explore how males and females may coevolve under sexual conflict over mating. This model shows that sexual conflict over mating results in the evolution of costly female mate choice, in terms high resistance to matings, and costly exaggerated male sexual traits, aimed to manipulate females into mating. A key assumption in this model is that males which females find attractive also are more harmful to females. This assumption was tested by housing fruit fly females with either attractive or unattractive males. Females kept with attractive males were courted and mated more, and suffered a 16 percent reduction in lifetime offspring production. In another study I measured genetic variation in two antagonistic male traits used to compete over females; offence - a male’s ability to acquire new mates and supplant stored sperm, and defence - a male’s ability to induce fidelity in his mates and prevent sperm displacement when remating occurs. Independent additive genetic variation and positive selection gradients were found for both these traits, indicating an ongoing arms race between these male antagonistic traits. This arms race also had a negative impact on females, since high values of offence compromised female fitness. Genetic variation in female ability to withstand male harm was also tested for and found, indicating that females evolve counter adaptations to reduce the effect of harmful male traits. Finally, the proposed link between sexual conflict and speciation was tested. Theory suggests that perpetual sexual arms races will cause allopatric populations to evolve along different evolutionary trajectories, resulting in speciation. This theory was tested using comparative methods by contrasting the number of extant species in taxa with high and low opportunity for sexual conflict. The study showed that taxa with high opportunity for sexual conflict, on average, has four times as many species as those with low opportunity, supporting that sexual conflict is a key process in speciation.

Place, publisher, year, edition, pages
Umeå: Ekologi, miljö och geovetenskap, 2006. 22 p.
cryptic male mate choice, Drosophila melanogaster, female mate choice, multiple mating, sexual conflict, sexually antagonistic coevolution, sexual selection, speciation, sperm competition
National Category
Biological Sciences
urn:nbn:se:umu:diva-735 (URN)91-7264-055-3 (ISBN)
Public defence
2006-04-20, KB3 A9, KBC-huset, Umeå, 10:00
Available from: 2006-03-30 Created: 2006-03-30Bibliographically approved

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