title: Adjustment of sperm allocation under high risk of sperm competition across taxa: a meta-analysis.
abstract: Sperm competition theory predicts that under high risk of sperm competition, males will increase the number of sperm that they allocate to a female. This prediction has been supported by some experimental studies but not by others. Here, I conducted a meta-analysis to determine whether the increase in sperm allocation under high risk of sperm competition is a generalized response across taxa. I collected data from 39 studies and 37 species. Across taxa, males under a high risk of sperm competition respond by increasing their sperm allocation (mean effect size=0.32). Number of offspring did not explain a significant portion of the variation in effect sizes. A traditional meta-analysis (i.e. without phylogenetic information) described the variation among effect sizes better than a meta-analysis that incorporates the phylogenetic relationships among species, suggesting that the increase in sperm allocation under high risk of sperm competition is similarly prevalent across taxa.
authors.affiliation: Department of Evolutionary Anthropology, Duke University, Durham, NC, USA. delbarcotrillo@gmail.com
authors.forename: J
authors.initials: J
authors.lastname: Delbarco-Trillo
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005260:Female; D008297:Male; D008954:Models, Biological; D010802:Phylogeny; D012726:Sexual Behavior, Animal; D013045:Species Specificity; D013094:Spermatozoa