Behavior, Ecology, Evolution and Systematics Group, School of Biological Sciences, Illinois State University, Normal, IL 61790-4120, USA.
Proc Biol Sci. 2012 Jul 7;279(1738):2531-8. doi: 10.1098/rspb.2011.2592. Epub 2012 Feb 22.
Nuptial food gifts function to enhance male fertilization success, but their consumption is not always beneficial to females. In decorated crickets, the spermatophore transferred at mating includes a gelatinous mass, the spermatophylax, which is consumed by females after mating. However, females often discard spermatophylaxes shortly after mating, whereupon they terminate sperm transfer. We hypothesized that females discard gifts based on their assessment of the gift itself, and specifically the composition of free amino acids. We tested this hypothesis by comparing spermatophylaxes discarded by females after mating with those that were destined to be fully consumed, and employed multivariate selection analysis to quantify the strength and form of multivariate sexual selection operating on the free amino acid composition of gifts. The analysis yielded a saddle-shaped fitness surface with two local peaks. Different amino acid profiles appear to elicit continued feeding on the spermatophylax either because they offer the same level of gustatory appeal, or because they differentially affect both the gustatory appeal and texture of the spermatophylax. We conclude that the gustatory response of females to males' nuptial food gifts represents an important avenue of post-copulatory mate choice, imposing significant sexual selection on the free amino acid composition of the spermatophylax.
交食礼物有助于提高雄性的受精成功率，但它们的消费并不总是对雌性有益。在装饰蟋蟀中，交配时传递的精荚包括一种胶状物质，即精荚，交配后雌性会将其吃掉。然而，雌性通常在交配后不久就丢弃精荚，从而终止精子传递。我们假设雌性根据礼物本身，特别是游离氨基酸的组成来评估礼物，并据此做出丢弃礼物的决定。我们通过比较交配后雌性丢弃的精荚和那些注定要被完全消耗的精荚，来验证这一假设，并采用多元选择分析来量化礼物中游离氨基酸组成所受到的多向性选择的强度和形式。分析得到一个鞍形适应面，有两个局部峰。不同的氨基酸图谱似乎会引发对精荚的持续进食，要么是因为它们提供了相同的味觉吸引力，要么是因为它们对精荚的味觉吸引力和质地产生了不同的影响。我们得出结论，雌性对雄性交食礼物的味觉反应代表了一个重要的交配后配偶选择途径，对精荚中的游离氨基酸组成产生了显著的性选择。
