In theory, a male should change the allocation of fighting and mating efforts in relation to his age. Thus, the consequences of sexual selection may be complicated by changes in the male resource allocation due to aging. However, previous studies have focused on changes in female mate choice and male-male competition with aging separately, and the impact of aging on the relationship between mate choice and male competition is unknown. Here, we examined how male competitiveness and attractiveness and their relationship changes over male lifespan in Gnatocerus cornutus. In this species, males perform courtship displays and fight rival males for mates. Older males are more competitive in male fighting and aggressive toward females than younger males. The aggression is also directed toward females. Almost all older males who attacked a female failed to copulate, while younger males never attacked the females. As a result, copulation success decreased with age. When an older male did not mistake a female for a male, he exhibited more frequent courtship. However, mating with older males imposed direct costs on females in terms of both fecundity and lifespan, with no offsetting indirect benefits for her offspring. The courtship behavior of older males does not supply females with cues for mate-choice benefits but are used to coerce females into mating. Our results suggest that male–male competition constrains female preference for older males. Thus, female choice and male–male competition may not be reinforcing in older G. cornutus males. When males get older, they often pay more attention to females in a variety of ways, such as courting and fighting for access. This is because older males have not long to live. In Gnatocerus cornutus as well, older males attend to fighting and courting. The older males seem to be competitive in male fights and attractive to females. However, they are not only aggressive toward rival males but also sometimes use violence on females. As a result, these older males are rejected by the assaulted females and cannot mate. Additionally, the violence of older males can reduce female fecundity and lifespan. Thus, mating with older males is costly to females in G. cornutus, and a female preference for older males is not expected to evolve.

中文翻译：

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年长的雄性在雄性战斗中更具竞争力，并且在宽角面粉甲虫 Gnatocerus cornutus 中对雌性更具攻击性

从理论上讲，雄性应该根据年龄改变战斗和交配努力的分配。因此，由于衰老导致男性资源分配发生变化，性选择的后果可能会变得复杂。然而，以往的研究分别关注女性择偶和男女竞争随年龄的变化，而年龄对择偶与男性竞争关系​​的影响尚不清楚。在这里，我们研究了 Gnatocerus cornutus 雄性竞争力和吸引力及其关系在雄性生命周期中的变化。在这个物种中，雄性进行求爱表演并与雄性竞争以寻找配偶。与年轻男性相比，年长男性在男性战斗中更具竞争力，对女性更具攻击性。攻击性也针对女性。几乎所有攻击雌性的年长雄性都未能交配，而年轻的雄性则从未攻击过雌性。结果，交配成功率随着年龄的增长而下降。当年长的雄性没有将雌性误认为雄性时，他表现出更频繁的求爱。然而，与年长的雄性交配在繁殖力和寿命方面给雌性带来了直接成本，而没有抵消对后代的间接好处。年长雄性的求偶行为不会为雌性提供择偶益处的线索，而是用来强迫雌性交配。我们的结果表明，男性与男性之间的竞争限制了女性对年长男性的偏好。因此，雌性选择和雄性竞争可能不会在年长的 G.cornutus 雄性中得到加强。随着男性年龄的增长，他们往往会以各种方式更加关注女性，例如求爱和争取访问权。这是因为老年男性的寿命不长。在 Gnatocerus cornutus 中，年长的雄性也会参与战斗和求爱。年长的雄性似乎在雄性打架中很有竞争力，对雌性很有吸引力。然而，它们不仅对敌对的雄性有攻击性，有时也会对雌性使用暴力。结果，这些年长的雄性被攻击的雌性拒绝，无法交配。此外，年长男性的暴力行为会降低女性的生育能力和寿命。因此，与年龄较大的雄性交配对 G.cornutus 中的雌性来说是昂贵的，并且预计不会进化出雌性对年长雄性的偏好。年长的雄性似乎在雄性打架中很有竞争力，对雌性很有吸引力。然而，它们不仅对敌对的雄性有攻击性，有时也会对雌性使用暴力。结果，这些年长的雄性被攻击的雌性拒绝，无法交配。此外，年长男性的暴力行为会降低女性的生育能力和寿命。因此，与年龄较大的雄性交配对 G.cornutus 中的雌性来说是昂贵的，并且预计不会进化出雌性对年长雄性的偏好。年长的雄性似乎在雄性打架中很有竞争力，对雌性很有吸引力。然而，它们不仅对敌对的雄性有攻击性，有时也会对雌性使用暴力。结果，这些年长的雄性被攻击的雌性拒绝，无法交配。此外，年长男性的暴力行为会降低女性的生育能力和寿命。因此，与年龄较大的雄性交配对 G.cornutus 中的雌性来说是昂贵的，并且预计不会进化出雌性对年长雄性的偏好。