Kawakami Takeshi, Butlin Roger K, Adams Mark, Paull David J, Cooper Steven J B
Evolutionary Biology Unit, South Australian Museum, SA, Australia.
Evolution. 2009 Jan;63(1):139-52. doi: 10.1111/j.1558-5646.2008.00526.x. Epub 2008 Sep 18.
Whether chromosomal rearrangements promote speciation by providing barriers to gene exchange between populations is one of the long-standing debates in evolutionary biology. This question can be addressed by studying patterns of gene flow and selection in hybrid zones between chromosomally diverse taxa. Here we present results of the first study of the genetic structure of a hybrid zone between chromosomal races of morabine grasshoppers Vandiemenella viatica, P24(XY) and viatica17, on Kangaroo Island, Australia. Chromosomal and 11 nuclear markers revealed a narrow hybrid zone with strong linkage disequilibrium and heterozygote deficits, most likely maintained by a balance between dispersal and selection. Widths and positions of clines for these markers are concordant and coincident, suggesting that selection is unlikely to be concentrated on a few chromosomes. In contrast, a mitochondrial marker showed a significantly wider cline with centre offset toward the P24(XY) side. We argue that the discordance between the mitochondrial and nuclear/chromosomal clines and overall asymmetry of the clines suggest a secondary origin of the contact zone and potential movement of the zone after contact. Genome-wide scans using many genetic markers and chromosomal mapping of these markers are needed to investigate whether chromosomal differences directly reduce gene flow after secondary contact.
染色体重排是否通过为种群间的基因交流提供障碍来促进物种形成，这是进化生物学中长期存在的争论之一。这个问题可以通过研究染色体不同分类群之间杂交区域的基因流动和选择模式来解决。在这里，我们展示了对澳大利亚袋鼠岛莫拉宾蝗虫（Vandiemenella viatica）的P24(XY)和viatica17染色体种族之间杂交区域遗传结构的首次研究结果。染色体和11个核标记揭示了一个狭窄的杂交区域，具有强烈的连锁不平衡和杂合子缺失，最有可能是由扩散和选择之间的平衡维持的。这些标记的渐变群宽度和位置是一致且重合的，这表明选择不太可能集中在少数几条染色体上。相比之下，一个线粒体标记显示出明显更宽的渐变群，其中心向P24(XY)一侧偏移。我们认为，线粒体和核/染色体渐变群之间的不一致以及渐变群的整体不对称表明接触区是次生起源的，并且在接触后该区域可能发生了移动。需要使用许多遗传标记进行全基因组扫描以及对这些标记进行染色体定位，以研究染色体差异在次生接触后是否直接减少了基因流动。
