Does habitat specialization shape the evolutionary potential of wild bird populations?

Because specialist species evolved in more temporally and spatially homogeneous environments than generalist species, they are supposed to experience less fluctuating selection. For this reason, we expect specialists to show lower overall genetic variation as compared to generalists. We also expect populations from specialist species to be smaller and more fragmented, with lower neutral genetic diversity. We tested these hypotheses by investigating patterns of genetic diversity along a habitat specialization gradient in wild birds, based on estimates of heritability, coefficients of variation of additive genetic variance, and heterozygosity available in the literature. We found no significant effect of habitat specialization on any of the quantitative genetic estimators but generalists had higher heterozygosity. This effect was mainly a consequence of the larger population size of generalists. Our results suggest that evolutionary potential does not differ at the population level betwee...由于特化物种（specialist species）相较于广适物种（generalist species），其演化所依托的时空环境具有更高的同质性，因此特化物种所经历的选择波动理应更小。基于此，我们推测特化物种的整体遗传变异水平低于广适物种。我们还提出假设：特化物种种群的规模更小且片段化程度更高，中性遗传多样性水平也更低。我们依托文献中已有的遗传力（heritability）、加性遗传方差（additive genetic variance）变异系数以及杂合度（heterozygosity）估算值，通过探究野生鸟类沿生境特化（habitat specialization）梯度的遗传多样性模式，对上述假说进行了检验。研究结果显示，生境特化对各类数量遗传估计量（quantitative genetic estimators）均无显著影响，但广适物种的杂合度更高。这一效应主要源于广适物种拥有更大的种群规模。我们的研究结果表明，种群层面的演化潜力在……之间并无差异。