Scheffer Sonja J, Hawthorne David J
Systematic Entomology Laboratory, Agricultural Research Service, US Department of Agriculture, BARC-W, 10300 Baltimore Avenue, Beltsville, MD 20705, USA.
Mol Ecol. 2007 Jul;16(13):2627-37. doi: 10.1111/j.1365-294X.2007.03303.x.
Host races play a central part in understanding the role of host plant mediated divergence and speciation of phytophagous insects. Of greatest interest are host-associated populations that have recently diverged; however, finding genetic evidence for very recent divergences is difficult because initially only a few loci are expected to evolve diagnostic differences. The holly leafminer Phytomyza glabricola feeds on two hollies, Ilex glabra and I. coriacea, that are broadly sympatric throughout most of their ranges. The leafminer is often present on both host plants and exhibits a dramatic life history difference on the two hosts, suggesting that host races may be present. We collected 1393 bp of mitochondrial cytochrome oxidase I (COI) sequence and amplified fragment length polymorphism (AFLP) data (45 polymorphic bands) from sympatric populations of flies reared from the two hosts. Phylogenetic and frequency analysis of mitochondrial COI sequence data uncovered considerable variation but no structuring by the host plant, and only limited differentiation among geographical locations. In contrast, analysis of AFLP frequency data found a significant effect with host plant, and a much smaller effect with geographical location. Likewise, neighbour-joining analysis of AFLP data resulted in clustering by host plant. The AFLP data indicate that P. glabricola is most likely comprised of two host races. Because there were no fixed differences in mitochondrial or AFLP data, this host-associated divergence is likely to have occurred very recently. P. glabricola therefore provides a new sympatric system for exploring the role of geography and ecological specialization in the speciation of phytophagous insects.
寄主族在理解寄主植物介导的植食性昆虫分化和物种形成的作用方面起着核心作用。最受关注的是最近分化的寄主相关种群；然而，找到最近分化的遗传证据很困难，因为最初预计只有少数基因座会进化出诊断性差异。冬青潜叶蝇Phytomyza glabricola以两种冬青属植物为食，即光滑冬青（Ilex glabra）和厚叶冬青（I. coriacea），这两种植物在其大部分分布范围内广泛同域分布。潜叶蝇通常在两种寄主植物上都有出现，并且在两种寄主上表现出显著的生活史差异，这表明可能存在寄主族。我们从两种寄主饲养的同域种群中收集了1393 bp的线粒体细胞色素氧化酶I（COI）序列以及扩增片段长度多态性（AFLP）数据（45个多态性条带）。线粒体COI序列数据的系统发育和频率分析发现了相当大的变异，但没有按寄主植物进行结构划分，并且地理位置之间只有有限的分化。相比之下，AFLP频率数据分析发现寄主植物有显著影响，而地理位置的影响要小得多。同样，AFLP数据的邻接法分析导致按寄主植物聚类。AFLP数据表明，光滑冬青潜叶蝇很可能由两个寄主族组成。由于线粒体或AFLP数据中没有固定差异，这种寄主相关的分化很可能是最近才发生的。因此，光滑冬青潜叶蝇为探索地理和生态特化在植食性昆虫物种形成中的作用提供了一个新的同域系统。
