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.