Python Script used in: Evolution of nuptial gifts and its coevolutionary dynamics with male-like persistence traits of females for multiple mating

Many male animals donate nutritive materials during courtship or mating to their female mates. Donation of large-sized gifts, though costly to prepare, can result in increased sperm transfer during mating and delayed remating of the females, resulting in a higher paternity. Nuptial gifting sometimes causes severe female-female competition for obtaining gifts (i.e., sex-role reversal in mate competition) and female polyandry, changing the intensity of sperm competition and the resultant paternity gains. We built a theoretical model to analyze such coevolutionary feedbacks between nuptial gift size (male trait) and propensity for multiple mating (female trait). Our genetically explicit, individual-based computer simulations demonstrate that a positive correlation between donated gift size and the resultant paternity gain is a requisite for the co-occurrence of large-sized gifts and females’ competitive multiple mating for the gifts. When gift donation imposes monandry, exaggeration of nuptial gift size also occurs under the assumption that the last male monopolizes paternity, although it reduces mating opportunities, also occurs under the assumption that the last male monopolizes paternity. We also analyzed the causes and consequences of the evolution of a female persistence trait in trading of nuptial gifts, that is, double receptacles for nuptial gifts known to occur in an insect group with a “female penis” (Neotrogla spp.).

众多雄性动物会在求偶或交配过程中，向雌性配偶提供营养物质。尽管大型求偶馈赠（nuptial gift）的制备成本高昂，但其可提升交配过程中的精子传递效率，并延缓雌性的再次交配行为，进而提升雄性的父权比例。求偶馈赠行为有时会引发激烈的雌性间竞争以获取馈赠（即配偶竞争中的性角色反转），并催生雌性一妻多夫现象，进而改变精子竞争的激烈程度与由此产生的父权收益。本研究构建了理论模型，用以分析求偶馈赠体型（雄性性状）与多次交配倾向（雌性性状）之间的这类协同进化反馈机制。本研究开展的遗传显式个体基计算机模拟实验表明，馈赠礼物体型与最终父权收益之间的正相关关系，是大型求偶馈赠与雌性为获取馈赠而进行竞争性多次交配共同出现的必要条件。当馈赠行为促使雌性实行单配制时，即便该行为会降低雄性的交配机会，但在最后雄性独占父权的假设前提下，求偶馈赠体型的夸张演化仍会发生。本研究还分析了雌性在求偶馈赠交易中的坚持演化性状的成因与演化结果——即已知存在于具有"雌性阴茎"的新颚虫属（Neotrogla spp.）昆虫类群中的、用于接收求偶馈赠的双接受器。