Data from: The red queen coupled with directional selection favors the evolution of sex

Why sexual reproduction has evolved to be such a widespread mode of reproduction remains a major question in evolutionary biology. While previous studies have shown that increased sex and recombination can evolve in the presence of host-parasite interactions (the “Red Queen hypothesis” for sex), many of these studies have assumed that multiple loci mediate infection versus resistance. Data suggest, however, that a major locus is typically involved in antigen presentation and recognition. Here, we explore a model where only one locus mediates host-parasite interactions, but a second locus is subject to directional selection. Even though the effects of these genes on fitness are independent, we show that increased rates of sex and recombination are favored at a modifier gene that alters the rate of genetic mixing. This result occurs because of selective interference that occurs in finite populations (the “Hill-Robertson effect”), which also favors sex. These results suggest that the Red Queen hypothesis may help to explain the evolution of sex by contributing a form of persistent selection, which interferes with directional selection at other loci and thereby favors sex and recombination.有性生殖为何能演化成为一种广泛存在的生殖方式，仍是进化生物学领域的核心未解科学问题之一。尽管已有研究表明，在宿主-寄生虫互作的情境下，有性生殖与重组的比例可得到提升并发生演化（该理论即针对有性生殖的红皇后假说（Red Queen hypothesis）），但此类研究大多假定，感染与抗性的调控由多个基因座（loci）介导。然而现有研究数据表明，抗原呈递与识别过程通常仅由单个主要基因座（locus）调控。本研究构建了仅单个基因座介导宿主-寄生虫互作、但存在第二个受定向选择（directional selection）的基因座的演化模型。尽管这两类基因对适合度（fitness）的影响相互独立，但我们的研究结果显示，能够改变遗传混合速率的修饰基因（modifier gene）若能提升有性生殖与重组的发生率，将更受自然选择青睐。该结果的成因是有限种群中存在的选择干涉现象，即希尔-罗伯逊效应（Hill-Robertson effect），该效应同样会推动有性生殖的演化。本研究结果表明，红皇后假说可通过引入一种持续性选择压力来助力解释有性生殖的演化：该选择压力会干扰其他基因座上的定向选择过程，进而促进有性生殖与重组的发生。