Department of Integrative Biology, University of California, Berkeley, CA 94720;
TruBreed Technologies, Oakland, CA 94609.
Proc Natl Acad Sci U S A. 2020 Dec 29;117(52):33373-33383. doi: 10.1073/pnas.2001337117. Epub 2020 Dec 14.
Natural selection is an important driver of genetic and phenotypic differentiation between species. For species in which potential gene flow is high but realized gene flow is low, adaptation via natural selection may be a particularly important force maintaining species. For a recent radiation of New World desert shrubs (: Asteraceae), we use fine-scale geographic sampling and population genomics to determine patterns of gene flow across two hybrid zones formed between two independent pairs of species with parapatric distributions. After finding evidence for extremely strong selection at both hybrid zones, we use a combination of field experiments, high-resolution imaging, and physiological measurements to determine the ecological basis for selection at one of the hybrid zones. Our results identify multiple ecological mechanisms of selection (drought, salinity, herbivory, and burial) that together are sufficient to maintain species boundaries despite high rates of hybridization. Given that multiple pairs of species hybridize at ecologically divergent parapatric boundaries, such mechanisms may maintain species boundaries throughout .
自然选择是物种间遗传和表型分化的重要驱动因素。对于潜在基因流动高但实际基因流动低的物种，通过自然选择进行适应可能是维持物种的特别重要的力量。对于新大陆荒漠灌木（菊科）的一个近期辐射，我们使用精细的地理采样和群体基因组学来确定两个杂交区之间的基因流动模式，这两个杂交区是由两个独立的、具有并系分布的物种对形成的。在发现两个杂交区都存在极强选择的证据后，我们结合野外实验、高分辨率成像和生理测量来确定一个杂交区选择的生态基础。我们的研究结果确定了多种选择的生态机制（干旱、盐度、食草和掩埋），这些机制共同足以维持物种边界，尽管存在高杂交率。鉴于多对物种在生态上不同的并系边界处杂交，这些机制可能在整个 中维持物种边界。
