Gene flow and the maintenance of species boundaries

Hybrid zones are regions where individuals from genetically differentiated populations meet and mate, resulting in at least some offspring of mixed ancestry. Patterns of gene flow (introgression) in hybrid zones vary across the genome, allowing assessment of the role of individual genes or genome regions in reproductive isolation. Here, we document patterns of introgression between two recently diverged species of field crickets. We sample at a very fine spatial scale and genotype crickets for 110 highly differentiated SNPs identified through transcriptome scans. Using both genomic and geographic cline analysis, we document remarkably abrupt transitions (less than 100 m) in allele frequencies for 50 loci, despite high levels of gene flow at other loci. These are among the steepest clines documented for any hybridizing taxa. Furthermore, the cricket hybrid zone provides one of the clearest examples of the semi-permeability of species boundaries. Comparisons between data from the fine sca...

杂交带（hybrid zone）是指来自遗传分化种群的个体相遇并交配，进而产生至少部分具有混合遗传祖源后代的区域。杂交带内的基因流（渐渗，introgression）模式在全基因组范围内存在差异，这为评估单个基因或基因组区域在生殖隔离中的作用提供了可行路径。本研究记录了两种新近分化的野外蟋蟀之间的渐渗模式：我们以极高的空间精细尺度开展采样，并通过转录组扫描鉴定出110个高度分化的单核苷酸多态性（Single Nucleotide Polymorphism, SNP）位点，用于蟋蟀的基因分型。结合基因组梯度分析与地理梯度分析，我们发现尽管其余位点存在高水平基因流，但50个位点的等位基因频率呈现出极为陡峭的过渡（跨度不足100米）。这类梯度属于已报道的杂交类群中最为陡峭的之一。此外，该蟋蟀杂交带是证明物种边界具有半渗透性的最清晰案例之一。对来自精细尺度下的[...]