Sex ratio schedules in a dynamic game: the effect of competitive asymmetry by male emergence order |
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Authors: | Abe Jun; Kamimura Yoshitaka; Shimada Masakazu |
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Institution: | a Department of Systems Sciences, University of Tokyo, Meguro, Tokyo 153-8902, Japan
b Faculty of Applied Biological Sciences, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan
c Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK
d Graduate School of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo 060-8589, Japan |
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Abstract: | Studies of sex allocation have provided some of the most successfultests of theory in behavioral and evolutionary ecology. Forinstance, local mate competition (LMC) theory has explainedvariation in sex allocation across numerous species. However,some patterns of sex ratio variation remain unexplained by existingtheory. Most existing models have ignored variation in malecompetitive ability and assumed all males have equal opportunitiesto mate within a patch. However, in some species experiencingLMC, males often fight fiercely for mates, such that male matingsuccess varies with male fighting ability. Here, we examinethe effect of competitive ability on optimal sex allocationschedules using a dynamic programming approach. This model assumesan asymmetric competitive ability derived from different mortalitiesaccording to the timing of male emergence. If the mortalityof newly emerging males is larger than that of already emergedmales, our model predicts a more female-biased sex ratio thanexpected under traditional LMC models. In addition, femalesare predicted to produce new males constantly at a low rateover the offspring emergence period. We show that our modelsuccessfully predicts the sex ratios produced by females ofthe parasitoid wasp Melittobia, a genus renowned for its vigorouslyfighting males and lower than expected sex ratios. |
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Keywords: | dynamic game model lethal male combat local mate competition Melittobia parasitoid wasps sex allocation |
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