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The Evolution of Continuous Variation in Ejaculate Expenditure Strategy

Tazzyman, SJ; Pizzari, T; Seymour, RM; Pomiankowski, A; (2009) The Evolution of Continuous Variation in Ejaculate Expenditure Strategy. The American Naturalist , 174 (3) E71 - E82. 10.1086/603612. Green open access

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Abstract

Sperm competition theory has largely focused on the evolution of ejaculate expenditure strategies across different species or populations or across discrete mating roles on which sperm competition operates differentially. Few studies have considered the extent to which male ejaculate expenditure is influenced by continuous change in male phenotype within a population. Here we model how optimal ejaculate expenditure responds to two sources of continuous variation: (1) the quantity of resources allocated by a male to mating within a breeding season and (2) the resource cost of obtaining a mate. We find that variation in the amount of resources available for mating does not alone produce selection for differing ejaculate investment strategies. However, when there is variation in the cost of obtaining a mate, males with a lower cost will be selected to invest fewer sperm per mating than males whose cost is higher. Any parameter decreasing this cost will also select for decreased ejaculate investment per mating. These results provide a novel insight into the evolution of male ejaculate expenditure strategies, revealing that individual constraints on the ability to secure matings can lead to variation in ejaculate expenditure even when the risk of sperm competition is the same for all males.

Type:Article
Title:The Evolution of Continuous Variation in Ejaculate Expenditure Strategy
Open access status:An open access version is available from UCL Discovery
DOI:10.1086/603612
Publisher version:http://dx.doi.org/10.1086/603612
Language:English
Additional information:© 2009 by The University of Chicago
Keywords:sperm competition, sexual selection, ornaments, fertility, SPERM COMPETITION GAMES, SEXUAL CONFLICT, SOCIAL-STATUS, TINY SPERM, MALES, FEMALES, SUCCESS, NUMBERS, QUALITY, MODELS
UCL classification:UCL > School of Life and Medical Sciences > Faculty of Life Sciences > Biosciences (Division of) > Genetics, Evolution and Environment
UCL > School of BEAMS > Faculty of Maths and Physical Sciences > CoMPLEX - Maths and Physics in the Life Sciences and Experimental Biology
UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Mathematics

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