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如此广泛的生殖模式，始终是进化生物学领域的核心未解问题。过往研究表明，在宿主-寄生虫互作（host-parasite interactions）情境下，有性生殖与重组的速率可得到提升，此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，感染与抗性由多个基因座（locus）共同介导。然而现有数据显示，抗原呈递与识别过程通常仅由单个主效基因座介导。本研究构建了如下模型：其中仅存在一个介导宿主-寄生虫互作的基因座，同时存在第二个受定向选择（directional selection）作用的基因座。尽管这两个基因对个体适合度（fitness）的效应相互独立，但我们的研究表明，在能够改变遗传混合速率的修饰基因（modifier gene）层面，更高的有性生殖与重组速率会受到正向选择的青睐。该结果的产生源于有限种群中存在的选择干扰（selective interference）现象——即希尔-罗伯逊效应（Hill-Robertson effect），这一效应同样会对有性生殖起到正向选择作用。上述结果表明，红皇后假说可通过引入一种持续选择的形式，对其他基因座上的定向选择造成干扰，进而推动有性生殖与重组受到正向选择，从而有助于解释有性生殖为何能演化为广泛存在的生殖模式。