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Differential investment in pre- versus post-copulatory sexual selection reinforces a cross-continental reversal of sexual size dimorphism in Sepsis punctum (Diptera: Sepsidae)


Puniamoorthy, Nalini; Blanckenhorn, Wolf U; Schäfer, Martin A (2012). Differential investment in pre- versus post-copulatory sexual selection reinforces a cross-continental reversal of sexual size dimorphism in Sepsis punctum (Diptera: Sepsidae). Journal of Evolutionary Biology, 25(11):2253-2263.

Abstract

Theory predicts that males have a limited amount of resources to invest inreproduction, suggesting a trade-off between traits that enhance mate acquisitionand those that enhance fertilization success. Here, we investigate therelationship between pre- and post-copulatory investment by comparing themating behaviour and reproductive morphology of four European and fiveNorth American populations of the dung fly Sepsis punctum (Diptera) thatdisplay a reversal of sexual size dimorphism (SSD). We show that the geographicreversal in SSD between the continents (male biased in Europe,female biased in North America) is accompanied by differential investmentin pre- vs. post-copulatory traits. We find higher remating rates in Europeanpopulations, where larger males acquire more matings and consequentlyhave evolved relatively larger testes and steeper hyper-allometry with bodysize. American populations, in sharp contrast, display much reduced, if any,effect of body size on those traits. Instead, North American males demonstratean increased investment in mate acquisition prior to copulation, withmore mounting attempts and a distinctive abdominal courtship display thatis completely absent in Europe. When controlling for body size, relativefemale spermathecal size is similar on both continents, so we find no directevidence for the co-evolution of male and female internal reproductivemorphology. By comparing allopatric populations of the same species thatapparently have evolved different mating systems and consequently SSD,we thus indirectly demonstrate differential investment in pre- vs. post-copulatorymechanisms increasing reproductive success.

Abstract

Theory predicts that males have a limited amount of resources to invest inreproduction, suggesting a trade-off between traits that enhance mate acquisitionand those that enhance fertilization success. Here, we investigate therelationship between pre- and post-copulatory investment by comparing themating behaviour and reproductive morphology of four European and fiveNorth American populations of the dung fly Sepsis punctum (Diptera) thatdisplay a reversal of sexual size dimorphism (SSD). We show that the geographicreversal in SSD between the continents (male biased in Europe,female biased in North America) is accompanied by differential investmentin pre- vs. post-copulatory traits. We find higher remating rates in Europeanpopulations, where larger males acquire more matings and consequentlyhave evolved relatively larger testes and steeper hyper-allometry with bodysize. American populations, in sharp contrast, display much reduced, if any,effect of body size on those traits. Instead, North American males demonstratean increased investment in mate acquisition prior to copulation, withmore mounting attempts and a distinctive abdominal courtship display thatis completely absent in Europe. When controlling for body size, relativefemale spermathecal size is similar on both continents, so we find no directevidence for the co-evolution of male and female internal reproductivemorphology. By comparing allopatric populations of the same species thatapparently have evolved different mating systems and consequently SSD,we thus indirectly demonstrate differential investment in pre- vs. post-copulatorymechanisms increasing reproductive success.

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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:2012
Deposited On:08 Mar 2013 14:12
Last Modified:07 Dec 2017 20:29
Publisher:Wiley-Blackwell
ISSN:1010-061X
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1111/j.1420-9101.2012.02605.x
PubMed ID:22984945

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