Eunuch supremacy: evolution of post-mating spider emasculation
Eunuch supremacy: evolution of post-mating spider emasculation
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DOI：
10.1007/s00265-014-1824-6
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发表时间：
2014
影响因子：
2.3
通讯作者：
Matjaž Kuntner;Urška Pristovšek;Ren-Chung Cheng;Daiqin Li;Shichang Zhang;I. Tso;Chen-Pan Liao;Jeremy A. Miller;S. Kralj-Fišer
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文献类型：
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作者：
Matjaž Kuntner;Urška Pristovšek;Ren-Chung Cheng;Daiqin Li;Shichang Zhang;I. Tso;Chen-Pan Liao;Jeremy A. Miller;S. Kralj-Fišer
去雄——雄性通过自我切除生殖器而实际上变得不育——长期以来一直被认为是一种功能未知的特殊进化现象，在分类学上仅限于少数蜘蛛和苍蝇。在蜘蛛中，当雄性切断一个或两个精子转移器官（触须）时，去雄会导致半或完全太监。蜘蛛有三种去雄方式，即成熟前、交配和交配后，它们都经过了多次进化。实行提前去雄的雄性在未成熟时切断其一只触须，然后通过生殖器堵塞和自发死亡进行严格的一夫一妻制。交配过程中的去雄也会导致生殖器堵塞，但一半太监还有另一次交配机会。到目前为止，那些在交配后通过自我切除毁容触须而成为太监的雄性的行为尚未得到实证研究。我们测试了硬币蜘蛛（Herennia multipuncta）交配后去雄的机制和适应性意义，并利用系统发育重建来了解其进化历史。我们的实验室分析证实了与配偶垄断相关的三个假设：（1）堵塞假说——预测生殖器堵塞以防止雌性再交配； （2）更好斗士假说——预测太监对对手的攻击性增强； (3) 不戴手套的假说——预测太监的忍耐力会增强。对蜘蛛在交配期间和之后进行去雄的假设的支持强化了最近对这两种去雄类型在蜘蛛科中进化上联系的系统发育解释。我们权衡了支持三种不同但同样简约的肾病去势进化情景的证据。我们的结论是，去势是一种适应性的、性选择的特征，需要进一步的比较和实验研究。
Emasculation—males becoming effectively sterile by self-removing their genitals—has long been considered a peculiar evolutionary phenomenon with unknown function, taxonomically restricted to few spiders and flies. In spiders, emasculation results in half or full eunuchs when males sever one or both sperm transferring organs, palps. Three types of emasculation,pre-maturation,mating, andpost-matingare known in spiders, all having evolved multiple times. Males practicing pre-maturation emasculation sever one of their palps while still immature, then engage in strict monogyny via genital plugging and spontaneous death. Emasculation during mating also results in genital plugs, but half eunuchs have another chance to mate. So far, the behavior of those males that become eunuchspost-matingby self-removing disfigured palps has not been investigated empirically. We test the mechanism and adaptive significance of post-mating emasculation in coin spiders (Herennia multipuncta) and use phylogenetic reconstruction to understand its evolutionary history. Our laboratory assays corroborate three hypotheses related to mate monopolization: (1) The plugging hypothesis—predicting genital plugs to prevent female remating; (2) The better-fighter hypothesis—predicting enhanced eunuch aggressiveness toward rivals; and (3) The gloves-off hypothesis—predicting increased eunuch endurance. The support for these hypotheses in spiders practicing emasculation during and after mating reinforces recent phylogenetic interpretations of these two emasculation types being evolutionarily linked in the family Nephilidae. We weigh the evidence in support of three different, but equally parsimonious scenarios of nephilid emasculation evolution. We conclude that emasculation is an adaptive, sexually selected trait that calls for further comparative and experimental research.