Lavoie Misha D, Tedeschi Jamie N, Garcia-Gonzalez Francisco, Firman Renée C
School of Biological Sciences (M092), Centre for Evolutionary Biology The University of Western Australia Crawley WA 6009 Australia.
Estacion Biológica de Doñana CSIC Sevilla Spain.
Evol Lett. 2019 Jun 27;3(4):392-402. doi: 10.1002/evl3.123. eCollection 2019 Aug.
Different stages during development are important when it comes to phenotypic adjustments in response to external stimuli. Critical stages in mammals are the prenatal phase, where embryos are exposed to a milieu of sex steroid hormones, and the early-postnatal phase, where littermates interact and experience their incipient social environment. Further, the postmaternal environment will influence the development of traits that are linked to reproductive success in adulthood. Accumulated evidence of male-driven sex allocation establishes the currently untested hypothesis that the sperm sex ratio is a plastic trait that can be mediated to align with prevailing social conditions. Here, we used natural variation in the maternal environment and experimentally manipulated the postmaternal environment to identify the importance of these developmental phases on sperm sex ratio adjustments in wild house mice (). We found that male density in both environments was predictive of sperm sex ratios at sexual maturity: males from more male-biased litters and males maturing under high male density produced elevated levels of Y-chromosome-bearing sperm. Our findings indicate that the sperm sex ratio is a variable phenotypic trait that responds to the external environment, and highlight the potential that these adjustments function as a mechanism of male-driven sex allocation.
在应对外部刺激进行表型调整时，发育过程中的不同阶段很重要。哺乳动物的关键阶段是产前阶段，胚胎在这个阶段会接触到性类固醇激素环境；以及出生后早期阶段，同窝幼崽在这个阶段相互作用并体验其初始社会环境。此外，产后环境会影响与成年期生殖成功相关的性状的发育。男性驱动的性别分配的累积证据确立了目前未经检验的假设，即精子性别比例是一种可塑性性状，可以被调节以与当前的社会条件相匹配。在这里，我们利用母体环境中的自然变异，并通过实验操纵产后环境，以确定这些发育阶段对野生家鼠精子性别比例调整的重要性。我们发现，两种环境中的雄性密度都能预测性成熟时的精子性别比例：来自雄性偏多窝的雄性以及在高雄性密度下成熟的雄性产生的携带Y染色体的精子水平升高。我们的研究结果表明，精子性别比例是一种可变的表型性状，对外部环境有反应，并突出了这些调整作为男性驱动的性别分配机制的潜力。
