Bull Vanessa, Beltrán Margarita, Jiggins Chris D, McMillan W Owen, Bermingham Eldredge, Mallet James
Galton Laboratory, Department of Biology, University College London, 4 Stephenson Way, London NW1 2HE, UK.
BMC Biol. 2006 Apr 21;4:11. doi: 10.1186/1741-7007-4-11.
The view that gene flow between related animal species is rare and evolutionarily unimportant largely antedates sensitive molecular techniques. Here we use DNA sequencing to investigate a pair of morphologically and ecologically divergent, non-sibling butterfly species, Heliconius cydno and H. melpomene (Lepidoptera: Nymphalidae), whose distributions overlap in Central and Northwestern South America.
In these taxa, we sequenced 30-45 haplotypes per locus of a mitochondrial region containing the genes for cytochrome oxidase subunits I and II (CoI/CoII), and intron-spanning fragments of three unlinked nuclear loci: triose-phosphate isomerase (Tpi), mannose-6-phosphate isomerase (Mpi) and cubitus interruptus (Ci) genes. A fifth gene, dopa decarboxylase (Ddc) produced sequence data likely to be from different duplicate loci in some of the taxa, and so was excluded. Mitochondrial and Tpi genealogies are consistent with reciprocal monophyly, whereas sympatric populations of the species in Panama share identical or similar Mpi and Ci haplotypes, giving rise to genealogical polyphyly at the species level despite evidence for rapid sequence divergence at these genes between geographic races of H. melpomene.
Recent transfer of Mpi haplotypes between species is strongly supported, but there is no evidence for introgression at the other three loci. Our results demonstrate that the boundaries between animal species can remain selectively porous to gene flow long after speciation, and that introgression, even between non-sibling species, can be an important factor in animal evolution. Interspecific gene flow is demonstrated here for the first time in Heliconius and may provide a route for the transfer of switch-gene adaptations for Müllerian mimicry. The results also forcefully demonstrate how reliance on a single locus may give an erroneous picture of the overall genealogical history of speciation and gene flow.
认为亲缘关系相近的动物物种之间的基因流动很少且在进化上不重要的观点，在灵敏的分子技术出现之前就已存在。在此，我们利用DNA测序技术研究了一对形态和生态上存在差异的非姐妹蝴蝶物种，即红带袖蝶（Heliconius cydno）和红袖蝶（H. melpomene）（鳞翅目：蛱蝶科），它们在南美洲中部和西北部的分布范围重叠。
在这些分类单元中，我们对线粒体区域每个位点的30 - 45个单倍型进行了测序，该线粒体区域包含细胞色素氧化酶亚基I和II（CoI/CoII）的基因，以及三个不连锁的核基因座的内含子跨度片段：磷酸丙糖异构酶（Tpi）、甘露糖-6-磷酸异构酶（Mpi）和肘脉中断基因（Ci）。第五个基因，多巴脱羧酶（Ddc）产生的序列数据可能来自某些分类单元中的不同重复基因座，因此被排除。线粒体和Tpi的系统发育关系与相互单系性一致，而巴拿马的同域分布种群共享相同或相似的Mpi和Ci单倍型，尽管有证据表明在红袖蝶的地理种群之间这些基因存在快速的序列分化，但在物种水平上仍产生了系统发育多系性。
有力支持了近期物种间Mpi单倍型的转移，但没有证据表明其他三个基因座存在基因渗入。我们的结果表明，动物物种之间的界限在物种形成后很长时间内可能对基因流动保持选择性的开放，并且基因渗入，即使是在非姐妹物种之间，也可能是动物进化中的一个重要因素。种间基因流动在此首次在红带袖蝶属中得到证实，并且可能为缪勒拟态的开关基因适应转移提供一条途径。这些结果还有力地证明了依赖单个基因座可能会给出物种形成和基因流动的整体系统发育历史的错误图景。
