CIBIO/InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos da Universidade do Porto, 4485-661, Vairão, Portugal.
Sci Rep. 2021 Jul 22;11(1):14970. doi: 10.1038/s41598-021-93897-z.
Sex differences in ornamentation are common and, in species with conventional sex roles, are generally thought of as stable, due to stronger sexual selection on males. Yet, especially in gregarious species, ornaments can also have non-sexual social functions, raising the possibility that observed sex differences in ornamentation are plastic. For example, females may invest in costly ornamentation more plastically, to protect body and reproductive ability in more adverse ecological conditions. We tested this hypothesis with experimental work on the mutually-ornamented common waxbill (Estrilda astrild), supplementing their diets either with pigmentary (lutein, a carotenoid) or non-pigmentary (vitamin E) antioxidants, or alleviating winter cold temperature. We found that both lutein and vitamin E supplementation increased red bill colour saturation in females, reaching the same mean saturation as males, which supports the hypothesis that female bill colour is more sensitive to environmental or physiological conditions. The effect of vitamin E, a non-pigment antioxidant, suggests that carotenoids were released from their antioxidant functions. Alleviating winter cold did not increase bill colour saturation in either sex, but increased the stability of female bill colour over time, suggesting that female investment in bill colour is sensitive to cold-mediated stress. Together, results show that waxbill bill sexual dichromatism is not stable. Instead, sexual dichromatism can be modulated, and even disappear completely, due to ecology-mediated plastic adjustments in female bill colour.
性二型在装饰上很常见，在具有传统性别角色的物种中，由于雄性受到更强的性选择，通常认为它们是稳定的。然而，特别是在群居物种中，装饰物也可能具有非性的社会功能，这增加了观察到的装饰物在性二型上的可塑性的可能性。例如，在更不利的生态条件下，雌性可能会更具可塑性地投资于昂贵的装饰物，以保护身体和生殖能力。我们通过对相互装饰的普通朱雀（Estrilda astrild）的实验工作检验了这一假设，在它们的饮食中补充色素（叶黄素，一种类胡萝卜素）或非色素（维生素 E）抗氧化剂，或缓解冬季寒冷温度。我们发现叶黄素和维生素 E 的补充都增加了雌性喙颜色饱和度，达到与雄性相同的平均饱和度，这支持了雌性喙颜色对环境或生理条件更敏感的假设。维生素 E（一种非色素抗氧化剂）的作用表明，类胡萝卜素从其抗氧化功能中释放出来。缓解冬季寒冷并没有增加两性的喙颜色饱和度，但增加了雌性喙颜色随时间的稳定性，这表明雌性对喙颜色的投资对寒冷介导的压力敏感。总之，结果表明朱雀喙的性二型性不稳定。相反，由于生态介导的雌性喙颜色的可塑性调整，性二型甚至可以完全消失。
