Tazzyman Samuel J, Pizzari Tommaso, Seymour Robert M, Pomiankowski Andrew
CoMPLEX (Centre for Mathematics and Physics in the Life Sciences and Experimental Biology), University College London, London WC1E 6BT, United Kingdom.
Am Nat. 2009 Sep;174(3):E71-82. doi: 10.1086/603612.
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.
精子竞争理论主要关注不同物种或种群间射精量策略的进化，或者关注精子竞争以不同方式起作用的离散交配角色间射精量策略的进化。很少有研究考虑在一个种群中，雄性射精量受雄性表型持续变化影响的程度。在此，我们构建模型来研究最优射精量如何应对两种持续变化的因素：（1）雄性在繁殖季节内分配给交配的资源数量；（2）获得配偶的资源成本。我们发现，可用于交配的资源量的变化本身并不会导致对不同射精投资策略的选择。然而，当获得配偶的成本存在差异时，与成本较高的雄性相比，成本较低的雄性会被选择在每次交配时投入更少的精子。任何降低这种成本的参数也会导致每次交配射精投资的减少。这些结果为雄性射精量策略的进化提供了新的见解，表明即使所有雄性面临的精子竞争风险相同，获得交配机会能力的个体限制也会导致射精量的差异。
