URFM, INRA, Avignon, France.
BioSP, INRA, Avignon, France.
Mol Ecol. 2018 Aug;27(15):3131-3145. doi: 10.1111/mec.14770. Epub 2018 Jul 11.
Interindividual variation in fecundities has major consequences on population evolutionary potential, through genetic drift and selection. Using two spatially explicit mating models that analyse the genotypes of seeds and seedlings, we investigated the variation of male and female fecundities within and among three European beech (Fagus sylvatica) stands situated along an altitudinal gradient. Female and male individual fecundity distributions were both skewed in this monoecious species, and we found a higher variance in female as compared to male fecundities. Both female and male fecundities increased with tree size and decreased with density and competition in the neighbourhood, the details of these effects suggesting sex-specific strategies to deal with the impact of limited resource on fecundity. The studied populations were functionally male-biased. Among-individual variations in functional gender were not driven by tree size but by density and competition in the neighbourhood. Femaleness decreased under limited resource availability, an expected consequence of the higher cost of female reproduction. Considering the variation of gene flow and genetic drift across elevation, our results suggest that the adaptive potential could be enhanced by low genetic drift at low elevation, and by high pollen-mediated gene flow at high elevation. Finally, this study predicts a more efficient response to selection for traits related to male vs. female fitness, for a given selection intensity.
个体间繁殖力的差异对种群进化潜力有重大影响，这种影响主要通过遗传漂变和选择产生。利用两种空间显式交配模型来分析种子和幼苗的基因型，我们研究了沿海拔梯度分布的三个欧洲山毛榉（Fagus sylvatica）林分中雌雄个体的繁殖力差异。在这个雌雄同体的物种中，雌性和雄性个体的繁殖力分布都是偏态的，并且我们发现雌性繁殖力的方差高于雄性繁殖力。雌性和雄性繁殖力都随树木大小增加而增加，随邻近密度和竞争减少而减少，这些效应的细节表明，雌雄个体具有不同的策略来应对资源有限对繁殖力的影响。研究的种群在功能上表现为雄性偏多。个体间功能性别差异不是由树的大小驱动的，而是由邻近的密度和竞争驱动的。在资源有限的情况下，雌性的比例会减少，这是雌性繁殖成本较高的预期结果。考虑到基因流和遗传漂变在海拔上的变化，我们的研究结果表明，在低海拔地区，遗传漂变较低，在高海拔地区，花粉介导的基因流较高，适应性潜力可能会增强。最后，本研究预测，在给定的选择强度下，与雄性和雌性适应性相关的性状对选择的反应可能更为有效。
