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Maintenance of sperm variation in a highly promiscuous wild bird


Calhim, S and Double, MC and Margraf, N and Birkhead, TR and Cockburn, A, Maintenance of sperm variation in a highly promiscuous wild bird, PLoS ONE, 6, (12) Article e28809. ISSN 1932-6203 (2011) [Refereed Article]


Copyright Statement

Copyright 2011 Calhim et al. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0)

DOI: doi:10.1371/journal.pone.0028809


Postcopulatory sexual selection is an important force in the evolution of reproductive traits, including sperm morphology. In birds, sperm morphology is known to be highly heritable and largely condition-independent. Theory predicts, and recent comparative work corroborates, that strong selection in such traits reduces intraspecific phenotypic variation. Here we show that some variation can be maintained despite extreme promiscuity, as a result of opposing, copulation-role-specific selection forces. After controlling for known correlates of siring success in the superb fairy-wren (Malurus cyaneus), we found that (a) lifetime extra-pair paternity success was associated with sperm with a shorter flagellum and relatively large head, and (b) males whose sperm had a longer flagellum and a relatively smaller head achieved higher within-pair paternity. In this species extrapair copulations occur in the same morning, but preceding, pair copulations during a female's fertile period, suggesting that shorter and relatively larger-headed sperm are most successful in securing storage (defense), whereas the opposite phenotype might be better at outcompeting stored sperm (offense). Furthermore, since cuckolding ability is a major contributor to differential male reproductive output, stronger selection on defense sperm competition traits might explain the short sperm of malurids relative to other promiscuous passerines.

Item Details

Item Type:Refereed Article
Keywords:animal cell, article, bird, cell structure, copulation, female, fertility, male
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Population ecology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the biological sciences
UTAS Author:Double, MC (Dr Michael Double)
ID Code:119640
Year Published:2011
Web of Science® Times Cited:30
Deposited By:Ecology and Biodiversity
Deposited On:2017-08-03
Last Modified:2017-10-16
Downloads:113 View Download Statistics

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