Comparative linkage maps suggest that fission, not polyploidy, underlies near-doubling of chromosome number within monkeyflowers (Mimulus; Phrymaceae)

Changes in chromosome number and structure are important contributors to adaptation, speciation, and macroevolution. In flowering plants, polyploidy and subsequent reductions in chromosome number by fusion are major sources of chromosomal evolution, but chromosome number increase by fission has been relatively unexplored. Here, we use comparative linkage mapping with gene-based markers to reconstruct chromosomal synteny within the model flowering plant genus Mimulus (monkeyflowers). Two sections of the genus with haploid numbers {greater than or equal to} 14 have been inferred to be relatively recent polyploids because they are phylogenetically nested within numerous taxa with low base numbers (n = 8-10). We combined multiple datasets to build integrated genetic maps of the M. guttatus species complex (section Simiolus, n = 14) and the M. lewisii group (section Erythranthe; n = 8), and then aligned the two integrated maps using >100 shared markers. We observed strong segmental synten...

染色体数目与结构的变异是适应、物种形成及宏观进化的重要驱动因素。在被子植物中，多倍体化及后续通过染色体融合实现的染色体数目缩减是染色体进化的主要来源，但通过染色体裂解导致的染色体数目增加现象，迄今尚未得到充分研究。本研究借助基于基因的分子标记开展比较连锁作图，对模式被子植物属——沟酸浆属（Mimulus，俗称猴面花）内的染色体同线性（synteny）进行重建。该属下两个组的单倍体染色体数目≥14，由于它们在系统发育上嵌入于众多染色体基数较低（n=8~10）的类群之中，因此被推测为相对较新的多倍体类群。我们整合多组数据集，分别构建了黄花沟酸浆（M. guttatus）物种复合群（Simiolus组，n=14）以及刘易斯沟酸浆类群（Erythranthe组，n=8）的整合遗传图谱，并通过100余个共享标记对两张整合图谱进行了比对对齐。我们观测到了强烈的片段同线性……