Genomewide variation provides insight into evolutionary relationships in a monkeyflower species complex (Mimulussect.Diplacus)

PREMISE OF THE STUDY: Evolutionary radiations provide excellent opportunities to study the origins of biodiversity, but rapid divergence and ongoing gene flow make inferring evolutionary relationships among taxa difficult. Consequently, multiple tools that combine morphological and genomic analyses may be necessary to provide a clear picture of relationships. We used an integrative approach to shed light on relationships within a diverse radiation of monkeyflowers (Mimulus section Diplacus) with a controversial taxonomic history. METHODS: Using genome-wide SNP data, we performed a combination of phylogenetic and population genomic analyses to infer the evolutionary relationships within the group. Tests for hybridization were performed to reveal sources of shared variation, and multivariate analyses of floral trait data were conducted to examine the relationship between phenotypic and phylogenetic information. KEY RESULTS: We identified four primary clades with evidence for some shared variation among them. We also detected evidence for recent gene flow between closely related subclades and populations. Strong discordance between floral trait and molecular data provides evidence for divergent and convergent phenotypic evolution. CONCLUSIONS: Mimulus section Diplacus exhibits all of the hallmarks of a rapid radiation, including diverse taxa that are at different stages of divergence, extensive shared variation among taxa, and complex patterns of phenotypic evolution. Our findings will direct future evolutionary research and have important taxonomic implications, highlighting the need for a new revision of section Diplacus.研究背景与前提：进化辐射（evolutionary radiation）是探究生物多样性起源的绝佳研究契机，但快速趋异与持续的基因流使得类群间演化关系的推断极具挑战性。因此，整合形态学与基因组学分析的多套研究工具或为必要手段，方能清晰厘清类群间的亲缘关系。本研究采用整合分析方法，对分类学历史存在争议的猴面花属二唇花组（Mimulus section Diplacus）这一多样化辐射类群的内部演化关系展开解析。 研究方法：本研究借助全基因组单核苷酸多态性（single nucleotide polymorphism, SNP）数据，联合开展系统发育与群体基因组学分析，以推断该类群的演化关系。通过杂交检验揭示共享变异的来源，并对花部性状数据进行多变量分析，以探究表型信息与系统发育信息之间的关联。 主要结果：本研究鉴定出四个主要演化支，各演化支间存在一定程度的共享变异；同时检测到亲缘关系较近的亚支与种群间存在近期基因流的证据。花部性状与分子数据间存在显著不一致，这为趋异与趋同表型演化提供了佐证。 研究结论：猴面花属二唇花组具备快速辐射演化的全部典型特征，包括处于不同趋异阶段的多样化类群、类群间广泛存在的共享变异，以及复杂的表型演化模式。本研究结果将为后续演化生物学研究提供指引，同时具有重要的分类学意义，凸显了对二唇花组开展重新修订的必要性。