Differential introgression causes genealogical discordance in host races of Acrocercops transecta (Insecta: Lepidoptera)

Recently diverged populations often exhibit incomplete reproductive isolation, with a low level of gene flow continuing between populations. Previous studies have shown that, even under a low level of gene flow, genetic divergence between populations can proceed at the loci governing local adaptation and reproductive isolation but not at other neutral loci. A leaf-mining moth, Acrocercops transecta, consists of Juglans- and Lyonia-associated host races. The two host races differ in host preferences of ovipositing females and in larval adaptation to host plants but mate readily in the laboratory, producing fertile hybrids. The Juglans and Lyonia races are often sympatric in the wild, implying that gene introgression could occur in nature between the two host races. We tested this hypothesis by combining phylogenetic analyses with coalescent simulations, focusing on mitochondrial genes (COI and ND5) and the nuclear Tpi, Per and Ldh genes located on the Z-chromosome. The mitochondria...新近分化的种群通常呈现不完全的生殖隔离（reproductive isolation），种群间仍存在低水平的基因流（gene flow）。既往研究表明，即便基因流水平较低，种群间的遗传分化仍可在调控局部适应与生殖隔离的基因座（locus，复数loci）上发生，而非中性基因座（neutral loci）则无此分化过程。一种潜叶蛾（Acrocercops transecta）存在两类寄主宗（host race）：分别以胡桃属（Juglans）和马醉木属（Lyonia）为寄主的种群。这两类寄主宗在产卵雌虫的寄主偏好以及幼虫对寄主植物的适应性上存在显著差异，但在实验室条件下可顺利交配并产生可育杂种。胡桃寄主宗与马醉木寄主宗在野外常呈同域分布（sympatric），这暗示两类寄主宗之间在自然环境中可能发生基因渐渗（gene introgression）。本研究通过结合系统发育分析（phylogenetic analyses）与溯祖模拟（coalescent simulations），聚焦线粒体基因（COI与ND5）以及位于Z染色体（Z-chromosome）上的核基因Tpi、Per与Ldh，对该假说展开验证。线粒体……