Laboratoire Evolution, Génomes et Spéciation, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France, Université Paris-SudXI, Orsay, France, Departamento de Biologia, Universidade Estadual Paulista, São José do Rio Preto, 15054-000, São Paulo, Brazil.
Mol Ecol Resour. 2008 May;8(3):491-501. doi: 10.1111/j.1471-8286.2007.02020.x.
Comparing introduced to ancestral populations within a phylogeographical context is crucial in any study aiming to understand the ecological genetics of an invasive species. Zaprionus indianus is a cosmopolitan drosophilid that has recently succeeded to expand its geographical range upon three continents (Africa, Asia and the Americas). We studied the distribution of mitochondrial DNA (mtDNA) haplotypes for two genes (CO-I and CO-II) among 23 geographical populations. mtDNA revealed the presence of two well-supported phylogenetic lineages (phylads), with bootstrap value of 100%. Phylad I included three African populations, reinforcing the African-origin hypothesis of the species. Within phylad II, a distinct phylogeographical pattern was discovered: Atlantic populations (from the Americas and Madeira) were closer to the ancestral African populations than to Eastern ones (from Madagascar, Middle East and India). This means that during its passage from endemism to cosmopolitanism, Z. indianus exhibited two independent radiations, the older (the Eastern) to the East, and the younger (the Atlantic) to the West. Discriminant function analysis using 13 morphometrical characters was also able to discriminate between the two molecular phylads (93.34 ± 1.67%), although detailed morphological analysis of male genitalia using scanning electron microscopy showed no significant differences. Finally, crossing experiments revealed the presence of reproductive barrier between populations from the two phylads, and further between populations within phylad I. Hence, a bona species status was assigned to two new, cryptic species: Zaprionus africanus and Zaprionus gabonicus, and both were encompassed along with Z. indianus and Zaprionus megalorchis into the indianus complex. The ecology of these two species reveals that they are forest dwellers, which explains their restricted endemic distribution, in contrast to their relative cosmopolitan Z. indianus, known to be a human-commensal. Our results reconfirm the great utility of mtDNA at both inter- and intraspecific analyses within the frame of an integrated taxonomical project.
在任何旨在了解入侵物种生态遗传学的研究中，比较一个系统发生地理学背景下的引入种群和祖先种群是至关重要的。扎普里诺乌斯属的印度实蝇是一种世界性的果蝇，最近已成功在三大洲（非洲、亚洲和美洲）扩大了其地理分布范围。我们研究了 23 个地理种群中两个基因（CO-I 和 CO-II）的线粒体 DNA（mtDNA）单倍型分布。mtDNA 揭示了两个支持度很好的系统发育分支（phylads）的存在，支持率为 100%。phylad I 包括三个非洲种群，这加强了该物种起源于非洲的假说。在 phylad II 内，发现了一个明显的地理分化模式：大西洋种群（来自美洲和马德拉群岛）与祖先的非洲种群比与东部种群（来自马达加斯加、中东和印度）更接近。这意味着，在从地方特有种到世界性分布的过程中，Z. indianus 表现出了两次独立的辐射，较老的（东部）向东部，较年轻的（大西洋）向西部。使用 13 个形态学特征的判别函数分析也能够区分两个分子 phylads（93.34±1.67%），尽管使用扫描电子显微镜对雄性生殖器进行的详细形态分析没有显示出显著差异。最后，杂交实验表明，两个phylads 之间的种群之间存在生殖障碍，phylad I 内的种群之间也存在生殖障碍。因此，两个新的、隐生的物种被赋予了一个真实的物种地位：扎普里诺乌斯非洲亚种和扎普里诺乌斯加蓬亚种，并且它们都与 Z. indianus 和扎普里诺乌斯巨喙亚种一起被纳入 indianus 复合体。这两个物种的生态学表明它们是森林生物，这解释了它们的有限地方特有分布，而相对世界性的 Z. indianus 则是人类共生物种。我们的研究结果再次证实了 mtDNA 在整合分类学项目中进行种间和种内分析的巨大作用。
