Sperm competition in tropical versus temperate zone birds

Sperm competition represents an important component of post-copulatory sexual selection. It has been argued that the level of sperm competition declines in birds towards the equator. However, to date, sperm competition estimates have been available mainly for avian species inhabiting the northern te...

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Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2013-02, Vol.280 (1752), p.20122434-20122434
Main Authors: Albrecht, Tomáš, Kleven, Oddmund, Kreisinger, Jakub, Laskemoen, Terje, Omotoriogun, Taiwo C., Ottosson, Ulf, Reif, Jiří, Sedláček, Ondřej, Hořák, David, Robertson, Raleigh J., Lifjeld, Jan T.
Format: Article
Language:English
Subjects:
Animal Migration
Animals
Body Size
Clutch Size
Ecosystem
Extra-Pair Paternity
Female
Life History
Male
Multivariate Analysis
Passeriformes - physiology
Post-Copulatory Sexual Selection
Seasons
Sexual Behavior, Animal
Sperm Phenotype
Spermatozoa - physiology
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Summary:Sperm competition represents an important component of post-copulatory sexual selection. It has been argued that the level of sperm competition declines in birds towards the equator. However, to date, sperm competition estimates have been available mainly for avian species inhabiting the northern temperate zone. Here we apply a novel approach, using the coefficient of between-male variation (CVbm) in sperm size as an index for sperm competition risk, in a comparative analysis of 31 Afrotropical and 99 northern temperate zone passerine species. We found no difference in sperm competition risk between the two groups, nor any relationship with migration distance. However, a multivariate model indicated that sperm competition risk was highest in species with a combination of low body mass and few eggs per clutch. The effect of clutch size was most pronounced in tropical species, which indicates that sperm competition risk in tropical and temperate species is differently associated with particular life-history traits. Although tropical species had lower sperm competition risk than temperate zone species for overlapping clutch sizes, the idea of a generally reduced risk of sperm competition in tropical birds was not supported by our analysis.
ISSN:0962-8452
1471-2945
1471-2954
DOI:10.1098/rspb.2012.2434