Chromosomal rearrangements and the genetics of reproductive barriers in Mimulus (monkeyflowers)

Chromosomal rearrangements may directly cause hybrid sterility and can facilitate speciation by preserving local adaptation in the face of gene flow. We used comparative linkage mapping with shared gene-based markers to identify potential chromosomal rearrangements between the sister monkeyflowers Mimulus lewisii and M. cardinalis, which are textbook examples of ecological speciation. We then re-mapped quantitative trait loci (QTLs) for floral traits and flowering time (pre-mating isolation) and hybrid sterility (post-zygotic isolation). We identified three major regions of recombination suppression in the M. lewisii x M. cardinalis hybrid map compared to a relatively collinear M. parishii x M. lewisii map, consistent with a reciprocal translocation and two inversions specific to M. cardinalis. These inferences were supported by targeted intra-specific mapping, which also implied a M. lewisii-specific reciprocal translocation causing chromosomal pseudo-linkage in both hybrid mapping pop...染色体重排（chromosomal rearrangements）可直接引发杂种不育，并可在基因流（gene flow）存在的条件下通过维持局部适应性促进物种形成（speciation）。本研究借助基于共享基因标记的比较连锁作图（comparative linkage mapping），在近缘猴面花（sister monkeyflowers）刘易斯猴面花（Mimulus lewisii）与红花猴面花（Mimulus cardinalis）之间鉴定潜在的染色体重排；二者是生态物种形成（ecological speciation）的经典教科案例。随后，我们对花部性状、开花时间（交配前生殖隔离，pre-mating isolation）以及杂种不育（合子后生殖隔离，post-zygotic isolation）的数量性状位点（quantitative trait loci，QTLs）进行了重新定位。相较于共线性较好的M. parishii × M. lewisii连锁图谱，本研究在M. lewisii × M. cardinalis的杂种连锁图谱中鉴定出3个显著的重组抑制（recombination suppression）区域，该结果与红花猴面花特有的1次相互易位（reciprocal translocation）和2次倒位（inversions）相一致。上述推论得到了靶向种内作图（targeted intra-specific mapping）的支持，该实验同时提示，1次刘易斯猴面花特有的相互易位会在两个杂种作图群体中引发染色体假连锁（chromosomal pseudo-linkage）……