A test of the chromosomal rearrangement model of speciation in Drosophila pseudoobscura

Recent studies suggest that chromosomal rearrangements play a significant role in speciation by preventing recombination and maintaining species persistence despite interspecies gene flow. Factors conferring adaptation or reproductive isolation are maintained in rearranged regions in the face of hybridization, while such factors are eliminated from collinear regions. As a direct test of this rearrangement model, we evaluated the genetic basis of hybrid male sterility in a sympatric species pair, Drosophila pseudoobscura pseudoobscura and D. persimilis, and an allopatric species pair, D. pseudoobscura bogotana and D. persimilis. Our results are consistent with the proposed model: virtually all of the sterility factors in the former pair are associated with three inverted regions, whereas sterility factors are present in the collinear regions in the latter pair. These findings indicate recombination and selection may have eliminated sterility factors outside the inverted regions between D. p. pseudoobscura and D. persimilis, suggesting chromosomal rearrangements may facilitate species persistence despite hybridization.

现有研究表明，染色体重排（chromosomal rearrangement）通过抑制遗传重组（recombination）、在存在跨物种基因流（interspecies gene flow）的情况下维持物种存续，在物种形成过程中发挥关键作用。面对杂交（hybridization）事件时，赋予适应性或生殖隔离（reproductive isolation）的因子会在重排区域中得以保留，而这类因子会从共线性区域（collinear regions）中被清除。为直接验证该重排模型，我们针对两组物种对开展了杂交雄性不育（hybrid male sterility）的遗传基础研究：一组为同域（sympatric）物种对——拟暗果蝇拟暗亚种（Drosophila pseudoobscura pseudoobscura）和拟小条果蝇（D. persimilis）；另一组为异域（allopatric）物种对——波哥大拟暗果蝇（D. pseudoobscura bogotana）和拟小条果蝇。本研究结果与该模型假说相符：前一组物种对中几乎所有不育因子均与三个倒位区域（inverted regions）相关，而后一组物种对的不育因子则存在于共线性区域中。上述结果表明，遗传重组与自然选择可能已清除了拟暗果蝇拟暗亚种与拟小条果蝇之间倒位区域外的不育因子，这暗示染色体重排可在杂交存在的情况下助力物种存续。