We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird.
- Authors
Calhim, Sara; Double, Michael C.; Margraf, Nicolas; Birkhead, Tim R.; Cockburn, Andrew
- Abstract
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.
- Subjects
FAIRY wrens; SPERMATOZOA; MALURUS cyaneus; SEXUAL ethics; PASSERIFORMES; SPERM competition; GENOTYPE-environment interaction
- Publication
PLoS ONE, 2011, Vol 6, Issue 12, p1
- ISSN
1932-6203
- Publication type
Article
- DOI
10.1371/journal.pone.0028809