Centre for Ecology and Conservation, Biosciences, University of Exeter, Penryn, Cornwall, United Kingdom.
PLoS One. 2013 May 22;8(5):e63807. doi: 10.1371/journal.pone.0063807. Print 2013.
Rapid and divergent evolution of male genital morphology is a conspicuous and general pattern across internally fertilizing animals. Rapid genital evolution is thought to be the result of sexual selection, and the role of natural selection in genital evolution remains controversial. However, natural and sexual selection are believed to act antagonistically on male genital form. We conducted an experimental evolution study to investigate the combined effects of natural and sexual selection on the genital-arch lobes of male Drosophila simulans. Replicate populations were forced to evolve under lifetime monogamy (relaxed sexual selection) or lifetime polyandry (elevated sexual selection) and two temperature regimes, 25°C (relaxed natural selection) or 27°C (elevated natural selection) in a fully factorial design. We found that natural and sexual selection plus their interaction caused genital evolution. Natural selection caused some aspects of genital form to evolve away from their sexually selected shape, whereas natural and sexual selection operated in the same direction for other shape components. Additionally, sexual and natural selection tended to favour larger genitals. Thus we find that the underlying selection driving genital evolution is complex, does not only involve sexual selection, and that natural selection and sexual selection do not always act antagonistically.
雌雄异体动物的雄性生殖器形态通常呈现快速且多样化的进化模式。这种快速的生殖器进化被认为是性选择的结果，而自然选择在生殖器进化中的作用仍然存在争议。然而，人们普遍认为，自然选择和性选择对雄性生殖器形态的作用是拮抗的。我们进行了一项实验进化研究，以探讨自然选择和性选择对雄性果蝇 simulans 的生殖器弓状突的联合作用。在完全析因设计中，我们将复制种群置于终生一夫一妻制（放松性选择）或终生多配偶制（提高性选择）以及 25°C（放松自然选择）或 27°C（提高自然选择）两种温度条件下，使其进化。我们发现，自然选择和性选择及其相互作用导致了生殖器的进化。自然选择使生殖器的某些形态特征偏离了其受性选择影响的形状，而自然选择和性选择对其他形态特征的作用方向是一致的。此外，性选择和自然选择往往有利于更大的生殖器。因此，我们发现，驱动生殖器进化的潜在选择是复杂的，不仅涉及性选择，而且自然选择和性选择并不总是相互拮抗的。
