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Population density and structure drive differential investment in pre- and postmating sexual traits in frogs


Lüpold, Stefan; Jin, Long; Liao, Wen Bo (2017). Population density and structure drive differential investment in pre- and postmating sexual traits in frogs. Evolution, 71(6):1686-1699.

Abstract

Sexual selection theory predicts a trade-off between premating (ornaments and armaments) and postmating (testes and ejaculates) sexual traits, assuming that growing and maintaining these traits is costly and that total reproductive investments are limited. The number of males in competition, the reproductive gains from investing in premating sexual traits, and the level of sperm competition are all predicted to influence how males allocate their finite resources to these traits. Yet, empirical examination of these predictions is currently scarce. Here, we studied relative expenditure on pre- and postmating sexual traits among frog species varying in their population density, operational sex ratio, and the number of competing males for each clutch of eggs. We found that the intensifying struggle to monopolize fertilizations as more and more males clasp the same female to fertilize her eggs shifts male reproductive investment toward sperm production and away from male weaponry. This shift, which is mediated by population density and the associated level of male–male competition, likely also explains the trade-off between pre- and postmating sexual traits in our much broader sample of anuran species. Our results highlight the power of such a multilevel approach in resolving the evolution of traits and allocation trade-offs.

Abstract

Sexual selection theory predicts a trade-off between premating (ornaments and armaments) and postmating (testes and ejaculates) sexual traits, assuming that growing and maintaining these traits is costly and that total reproductive investments are limited. The number of males in competition, the reproductive gains from investing in premating sexual traits, and the level of sperm competition are all predicted to influence how males allocate their finite resources to these traits. Yet, empirical examination of these predictions is currently scarce. Here, we studied relative expenditure on pre- and postmating sexual traits among frog species varying in their population density, operational sex ratio, and the number of competing males for each clutch of eggs. We found that the intensifying struggle to monopolize fertilizations as more and more males clasp the same female to fertilize her eggs shifts male reproductive investment toward sperm production and away from male weaponry. This shift, which is mediated by population density and the associated level of male–male competition, likely also explains the trade-off between pre- and postmating sexual traits in our much broader sample of anuran species. Our results highlight the power of such a multilevel approach in resolving the evolution of traits and allocation trade-offs.

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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)
Uncontrolled Keywords:Anura; multi-male amplexus; polyandry; resource allocation; sexual selection; sperm competition; trade-off
Language:English
Date:June 2017
Deposited On:27 Dec 2017 14:31
Last Modified:18 Apr 2018 11:49
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0014-3820
Funders:Swiss National Science Foundation, National Natural Sciences Foundation of China, Sichuan Province Outstanding Youth Academic Technology Leaders Program, Sichuan Province Department of Education Innovation Team Project
OA Status:Closed
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1111/evo.13246
PubMed ID:28394412
Project Information:
  • : FunderSNSF
  • : Grant ID
  • : Project TitleSwiss National Science Foundation
  • : Funder
  • : Grant ID
  • : Project TitleNational Natural Sciences Foundation of China
  • : Funder
  • : Grant ID
  • : Project TitleSichuan Province Outstanding Youth Academic Technology Leaders Program
  • : Funder
  • : Grant ID
  • : Project TitleSichuan Province Department of Education Innovation Team Project

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