Biological Sciences Department, California Polytechnic State University, San Luis Obispo, CA 93407, USA.
Biological Sciences Department, California Polytechnic State University, San Luis Obispo, CA 93407, USA.
Behav Processes. 2024 Oct;222:105096. doi: 10.1016/j.beproc.2024.105096. Epub 2024 Sep 14.
The maintenance of variation within natural populations is key for natural selection to operate. Polymorphism is an intriguing form of variation that involves the persistence of multiple discrete phenotypes called morphs. Polymorphism is often explained by negative frequency dependent selection (NFDS), under which rare morphs have an advantage, such that no one morph takes over. We tested whether mating polymorphism is maintained by NFDS generated by female choice, in the livebearing poeciliid fish, Girardinus metallicus, whose males are either common, plain morphs or rare, black morphs. Females were treated with one morph for several weeks and tested with both, in mate choice and direct competition assays. Contrary to NFDS via female choice, females preferred the morph with which they were treated. This may disrupt the polymorphism given the rarity of black morphs in the wild, unless black morphs have other advantages: we found that black morphs tended to exhibit higher mating activity, and other studies have demonstrated that they are more aggressive. Interestingly, only black morphs display to females prior to copulation; however, there is little evidence for female preference for this morph or the mating display. These results suggest functions for the mating display of black morphs beyond courtship, including aggressive mate guarding, and prompt a discussion of what constitutes courtship behavior.
自然种群中变异的维持是自然选择发挥作用的关键。多态性是一种有趣的变异形式，它涉及到多种离散表型（称为形态）的持续存在。多态性通常可以用负频率依赖选择（NFDS）来解释，在这种选择下，稀有形态具有优势，以至于没有一种形态会占据主导地位。我们测试了在胎生脂鲤科鱼类吉拉迪努斯金属鱼中，由雌性选择产生的 NFDS 是否维持了交配多态性，其雄性有普通的、朴素的形态或稀有的、黑色的形态。雌性被用一种形态处理数周，然后在选择伴侣和直接竞争实验中用两种形态进行测试。与通过雌性选择的 NFDS 相反，雌性更喜欢与它们接触过的形态。这可能会破坏多态性，因为在野外黑色形态很少见，除非黑色形态有其他优势：我们发现黑色形态往往表现出更高的交配活动，而其他研究表明它们更具攻击性。有趣的是，只有黑色形态在交配前向雌性展示；然而，几乎没有证据表明雌性对这种形态或交配展示有偏好。这些结果表明，黑色形态的交配展示除了求偶之外还有其他功能，包括攻击性的伴侣保护，并促使人们讨论什么是求偶行为。
