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Disruptive sexual selection on male body size in the polyphenic black scavenger fly Sepsis thoracica


Busso, Juan Pablo; Blanckenhorn, Wolf U (2018). Disruptive sexual selection on male body size in the polyphenic black scavenger fly Sepsis thoracica. Behavioral Ecology, 29(3):769-777.

Abstract

Sexual selection has 2 main components, female preference and male–male competition, which can lead males to adopt alternative reproductive tactics to optimize their reproductive success. Two traits that significantly influence reproductive success are body size and coloration, as they can facilitate access to females through male contests or as female attractors. We investigated whether, and if so which mechanism of sexual selection contributes to the maintenance, and possibly even the establishment, of 2 almost discrete male morphs in the polyphenic black scavenger fly Sepsis thoracica (Diptera: Sepsidae): small and black, or large and amber. We performed 2 complementary laboratory experiments to evaluate the mating success of the different male morphs and the behaviors (of both males and females) presumably mediating their mating success. We found evidence for intraspecific disruptive sexual selection on male body size that is mediated by male–male interactions, and significant positive directional selection on body size that interacted with (directional) selection on coloration, likely contributing to the origin and/or maintenance of the threshold relationship between the 2 traits in this species. The simultaneous occurrence of disruptive selection and polyphenism in S. thoracica supports the role of sexual selection in the intraspecific diversification of coupled traits (here body size and coloration), which could be a speciation starting point.

Abstract

Sexual selection has 2 main components, female preference and male–male competition, which can lead males to adopt alternative reproductive tactics to optimize their reproductive success. Two traits that significantly influence reproductive success are body size and coloration, as they can facilitate access to females through male contests or as female attractors. We investigated whether, and if so which mechanism of sexual selection contributes to the maintenance, and possibly even the establishment, of 2 almost discrete male morphs in the polyphenic black scavenger fly Sepsis thoracica (Diptera: Sepsidae): small and black, or large and amber. We performed 2 complementary laboratory experiments to evaluate the mating success of the different male morphs and the behaviors (of both males and females) presumably mediating their mating success. We found evidence for intraspecific disruptive sexual selection on male body size that is mediated by male–male interactions, and significant positive directional selection on body size that interacted with (directional) selection on coloration, likely contributing to the origin and/or maintenance of the threshold relationship between the 2 traits in this species. The simultaneous occurrence of disruptive selection and polyphenism in S. thoracica supports the role of sexual selection in the intraspecific diversification of coupled traits (here body size and coloration), which could be a speciation starting point.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2018
Deposited On:04 Oct 2018 12:44
Last Modified:24 Sep 2019 23:48
Publisher:Oxford University Press
ISSN:1045-2249
OA Status:Closed
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1093/beheco/ary038
Official URL:https://academic.oup.com/beheco/article/29/3/769/4961326

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