A phylogenomic rodent tree reveals the repeated evolution of masseter architectures

Understanding the number of times a trait has evolved is a necessary foundation for comprehending its potential relationships with selective regimes, developmental constraints, and evolutionary diversification. Rodents make up over 40% extant of mammalian species and their ecological and evolutionary success has been partially attributed to the increase in biting efficiency that resulted from a forward shift of one or two portions of the masseter muscle from the zygomatic arch onto the rostrum. This forward shift has occurred in three discrete ways, but the number of times it has occurred has never been explicitly quantified. We estimated an ultrametric phylogeny, the first to include all rodent families, using thousands of ultraconserved elements. We examined support for evolutionary relationships among the five rodent suborders and then incorporated relevant fossils, fit models of character evolution, and used stochastic character mapping to determine that a portion of the masseter mu...解析某一性状的演化次数，是理解其与选择制度（selective regimes）、发育限制以及演化辐射之间潜在关联的必要基础。啮齿类占现存哺乳动物物种总数的40%以上，其生态与演化上的成功，部分归因于咬合力效率的提升——这一提升源于咬肌（masseter muscle）的1至2个束支从颧弓（zygomatic arch）向前移位至吻部（rostrum）。该向前移位现象存在三种独立模式，但此前从未有研究对其发生次数进行明确量化。本研究借助数千个超保守元件（ultraconserved elements），构建了首个涵盖所有啮齿类科的超度量系统发育树。我们评估了啮齿类五个亚目之间演化关系的支持证据，随后整合相关化石数据、拟合性状演化模型，并采用随机性状映射（stochastic character mapping）方法，明确了咬肌部分束支的……