性爱:冲突还是合作? - 来自一种多配型甲虫木棉眉斑并脊天牛的实验证据

Sexual selection and sexual conflict are a central concern in evolutionary biology. The theory of sexual selection is now well accepted and relatively well studied across animal taxa, particularly insects and birds. The concept of sexual conflict, however, is relatively new. So far, experimental evidence is still largely lacking in determination of whether sexual conflict or sexual selection is responsible for the observed antagonistic behaviors between sexes. This bottle neck has significantly limited our understanding of these two evolutionary forces. Glenea cantor is a polygamous beetle where both sexes can mate multiply in their lifetime but after the first mating, females strongly resist against males’ mating attempt, resulting in complicated antagonistic interactions between sexes. Furthermore, we have a good understanding of reproductive behavior and sexual selection of G. cantor through our previous studies. Therefore, this beetle is an ideal animal for antagonistic behavioral studies. Here we propose to investigate the behavioral and morphological traits during sexual antagonistic interactions and their association with mating success and fitness gain and loss, with three objectives: (1) to estimate the evolution of traits resulting from sexual selection and sexual conflict, (2) to determine whether sexual conflict or sexual selection plays the main role in observed sexual antagonistic behavior, and (3) to determine the evolution of fitness traits resulting from sexual selection and sexual conflict. The completion of this project will provide critical experimental evidence from a polygamous beetle for the understanding of the mechanisms behind sexual selection and sexual conflict which is of significant importance in both theory and practice for organisms that reproduce sexually.

性选择和性冲突是当前进化生物学研究领域的热点之一。性选择理论已被广泛接受，而性冲突概念的提出则相对较晚。目前尚无足够的实验证据证明所观察到的性对抗行为是由性选择还是性冲突起决定性作用。该瓶颈问题极大地限制人们对这两个进化动力的理解。木棉眉斑并脊天牛是一种多配型昆虫，雌雄虫一生均可多次交配，但经过一次交配后，雌虫对雄虫的交配企图表现出强烈的抵制行为，导致两性间出现复杂的性拮抗，是研究性拮抗行为的好材料。我们在已了解其繁殖行为和性选择的基础上，拟研究与性拮抗有关的行为和形态特征及其与交配成功率的关系；雌雄虫在性拮抗关系中的利益和损失。本项目的目的是：1) 评估性选择和性冲突所导致的性状进化；2) 明确其性拮抗行为到底是性冲突还是性选择起主导作用；3) 评价由性选择和性冲突导致的适合度特征的进化。该研究的完成，将为性选择和性冲突机制提供关键性的实验证据，在两性生殖的理论和实践中具有重要科学价值。

性选择和性冲突是当前进化生物学研究领域的热点之一。性选择理论已被广泛接受，而性冲突概念的提出则相对较晚。目前尚无足够的实验证据证明所观察到的性对抗行为是由性选择.还是性冲突起决定性作用。该瓶颈问题极大地限制人们对这两个进化动力的理解。本项目以多配型昆虫眉斑并脊天牛为对象，采用行为学观察方法，系统研究成虫的拒绝交配行为、与性拮抗作用有关的行为和形态学特征及其与交配成功率的关系、性拮抗作用的利益和损失。结果表明，雌虫在首次交配后存在明显的拒绝交配行为，拒绝交配期平均为13.56±8.97d，而一旦雌虫接受第二次交配，其会更容易接受再交配；在1♀:5♂偏雄性比下，雄虫的交配率为51.67%，明显低于1♀:3♂和1♀:2♂的雄虫平均交配率，偏雄性比可缩短雌虫的拒绝交配期，但雌虫的交配次数并无显著增多；后足跗节长在2.97mm以上的雄性个体，其成功交配率达95.5%，显著(P<0.05)高于后足跗节长在2.59mm以下的个体（63.6%），表明其后足跗节的长度和抱握力度在对抗雌虫的后踢动作中起到重要作用，是雄虫繁殖适度的指示特征，它们在性选择和性拮抗进化中要承受更大的选择压力；在交配过程中，雄虫始终表现出强烈的抱握、搂抱和持续的曲腹、生殖器插入动作，表明雄虫在交配过程中为获得父权而使其利益最大化；雌虫主要选择体重在0.120-0.130g的雄虫个体交配，交配率达94.3%，但在首次交配后，其对不同个体大小、年龄、交配经历的雄虫均表现强烈的拒绝交配行为，且雌虫再交配并不能提高其产卵量和卵的孵化率，表明雌虫在多次交配中并未获得益处，雌虫对雄虫的交配企图表现出强烈的抵制行为属于性冲突行为，雌虫接受再交配是为了降低雄虫持续不断的企图交配干扰所带来的风险而采取的顺从行为。研究结果为科学解读性选择和性冲突机制提供关键实验证据，在两性生殖的理论和实践中具有重要科学价值。