Abstract Chromosomal evolution is widely considered an important driver of speciation because it can promote the establishment of reproductive barriers. Karyotypic reorganization is also expected to affect the mean phenotype, as well as its development and patterns of phenotypic integration, through processes such as variation in genetic linkage between quantitative trait loci or between regulatory regions and their targets. Here we explore the relationship between chromosomal evolution and phenotypic integration by analyzing a well-known house mouse parapatric contact zone between a highly derived Robertsonian (Rb) race (2n = 22) and populations with standard karyotype (2n = 40). Populations with hybrid karyotypes are scattered throughout the hybrid zone connecting the two parental races. Using mandible shape data and geometric morphometrics, we test the hypothesis that patterns of integration progressively diverge from the “normal” integration pattern observed in the standard race as they accumulate Rb fusions. We find that the main pattern of integration observed between the posterior and anterior part of the mandible can be largely attributed to allometry. We find no support for a gradual increase in divergence from normal patterns of integration as fusions accumulate. Surprisingly, however, we find that the derived Rb race (2n = 22) has a distinct allometric trajectory compared with the standard race. Our results suggest that either individual fusions disproportionately affect patterns of integration or that there are mechanisms which “purge” extreme variants in hybrids (e.g. reduced fitness of hybrid shape).

中文翻译：

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随着染色体融合数量的增加，与正常整合模式的差异是否会增加？家鼠杂交区的测试

摘要 染色体进化被广泛认为是物种形成的重要驱动因素，因为它可以促进生殖屏障的建立。预计核型重组也会通过数量性状基因座之间或调控区域与其目标之间的遗传连锁变异等过程影响平均表型及其发展和表型整合模式。在这里，我们通过分析高度派生的罗伯逊 (Rb) 种族 (2n = 22) 和标准核型种群 (2n = 40) 之间众所周知的家鼠旁系接触区来探索染色体进化和表型整合之间的关系。具有杂交核型的种群分散在连接两个亲本种族的杂交区中。使用下颌骨形状数据和几何形态测量学，我们检验了这样一个假设，即随着他们积累 Rb 融合，整合模式逐渐偏离在标准种族中观察到的“正常”整合模式。我们发现在下颌骨的后部和前部之间观察到的主要整合模式在很大程度上可以归因于异速生长。我们发现，随着融合的积累，与正常整合模式的分歧逐渐增加没有任何支持。然而，令人惊讶的是，我们发现衍生的 Rb 种族（2n = 22）与标准种族相比具有明显的异速生长轨迹。我们的结果表明，要么单个融合不成比例地影响整合模式，要么存在“清除”杂交中极端变异的机制（例如，杂交形状的适应性降低）。