Abstract

Male sensory exploitation of female gustatory pre-existing bias has been proposed for the origin of nuptial gifts in insects and spiders. This sexual trait may have been beneficial to both sexes, giving mating and survival advantages to males and providing nutritional resources for females. However, the evolution of deceptive worthless gifts is against females’ interests and may trigger a co-evolutionary change in females’ preferences. We evaluated females’ preferences for nuptial gifts and the adaptive function of the gift in the spider Trechaleoides keyserlingi. The genus belongs to the understudied Neotropical family Trechaleidae in which nuptial gifts are widespread. The family is composed of only two species, and the gift seems to be absent in the sister species, creating a relevant scenario for understanding co-evolutionary processes. In the laboratory, we found that although males invested more in nuptial gifts when encountering mated females compared to unmated, they had similar mating access and duration than males lacking a gift. We also found an absence of female choice between males offering nutritive and worthless gifts. Few females were aggressive and cannibalized males, and we did not find evidence that the gift protected males from cannibalism. In the field, 50% of the gifts were worthless items. This is congruent with the laboratory findings where males offering worthless gifts seem to better attract females, which we discuss in the context of exploitation of female gustatory bias. We therefore propose that females may have evolved indifference for the gift and that gift-giving in this species represents a currently non-functional remnant of a behaviour.

Significance statement

Nutritive nuptial gifts can exploit female gustatory preferences, with mutual benefits for both sexes: males can increase mating success and survival, while females increase their fecundity. But males can offer worthless gifts leading females to suboptimal matings, and in turn females can evolve indifference for the trait. The spider genus Trechaleoides is ideal to examine this process because gift-giving behaviour is present in one species and absent in the other. We examined females’ preferences for nuptial gifts and its function for males in the gift-giving species T. keyserlingi. We found that males invest in a gift but gain no reproductive advantage, as females were equally likely to mate with them regardless of whether they offered a gift or whether the gift was nutritive or worthless. We propose that females may have changed their preferences and that the gift is a remnant non-functional trait.

中文翻译：

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无效的结婚礼物表明女性从感官剥削中解放了

摘要

男性对雌性味觉先前存在的偏见的感觉开发已被提议用于昆虫和蜘蛛中的结婚礼物的起源。这种性状可能对男女双方都有利，为雄性提供了交配和生存优势，并为雌性提供了营养资源。然而，欺骗性的毫无价值的礼物的发展违背了女性的利益，并可能引发女性偏好的共同演变。我们评估了女性对婚庆礼物的偏好以及蜘蛛Trechaleoides keyserlingi中礼物的适应功能。该属属于人们研究不足的新热带家庭千金龟科。该家族仅由两个物种组成，而姐妹物种似乎没有该天赋，为理解共同进化过程创造了一个相关场景。在实验室中，我们发现尽管与未交配的雌性相比，雄性在与交配的雌性交配时对婚庆礼物的投入更多，但与没有交配的雄性相比，他们拥有相似的交配途径和持续时间。我们还发现，在提供营养和毫无价值的礼物的男性之间没有女性的选择。很少有女性是好斗的和被人食人的男性，而且我们没有发现证据表明礼物可以保护男性免于自相残杀。在实地，50％的礼物都是毫无价值的物品。这与实验室发现相吻合，在实验室发现中，提供无价值礼物的雄性似乎更好地吸引了雌性，我们在利用女性味觉偏向的背景下进行了讨论。因此，我们建议雌性对礼物的态度可能变得冷漠，并且该物种的礼物赠送代表了当前行为的无功能残留。

重要性声明

营养性结婚礼物可以利用女性的味觉偏好，对男女双方都有共同的好处：雄性可以增加交配的成功率和存活率，而雌性则可以增加繁殖力。但是雄性会提供毫无价值的礼物，导致雌性交配不理想，反过来，雌性也会对性格变得冷漠。蜘蛛属Trechaleoides是检查此过程的理想选择，因为在一个物种中存在送礼行为，而在另一个物种中则不存在。我们研究了女性对送礼的偏爱及其在送礼物种T中对男性的作用。Keyslingi。我们发现，男性投资礼物却没有获得生殖优势，因为女性无论是否提供礼物，礼物是否营养或毫无价值，都同样有可能与他们交配。我们建议女性可能已经改变了自己的喜好，并且礼物是残余的非功能性特征。