Phylogeny, classification, and character evolution of tribe Citharexyleae (Verbenaceae)

FROST, LAURA; O'LEARY, NATALY; LAGOMARSINO, LAURA; TANK, DAVID; OLMSTEAD, RICHARD

AMERICAN JOURNAL OF BOTANY

BOTANICAL SOC AMER INC

Lugar: St. Louis; Año: 2021 vol. 108 p. 1982 - 2001

0002-9122

Premise: As a family of Neotropical origin and primarily Neotropical distribution, theVerbenaceae are a good but understudied system with which to understandNeotropical evolution. Tribe Citharexyleae comprises three genera: Baillonia,Citharexylum?one of the largest genera in Verbenaceae?and Rehdera. A molecularphylogenetic approach was taken to resolve intergeneric relationships in Citharexyleaeand infrageneric relationships in Citharexylum. The phylogeny is used to elucidatecharacter evolution in a widespread, morphologically diverse Neotropical genus.Methods: Seven plastid regions, two nuclear ribosomal spacers, and six low‐copynuclear loci were analyzed for 64 species of Citharexyleae. Phylogenetic analyses wereconducted using maximum likelihood, Bayesian inference, and multispecies coalescent approaches. Habit, presence or absence of thorns, inflorescence architecture,flower color, fruit color, and geography were examined to identify diagnosticcharacter states for clades within Citharexylum.Results: Rehdera is resolved as sister to Citharexylum, and Baillonia nested withinCitharexylum. Two species, C. oleinum and C. tetramerum, are not closely related totribe Citharexyleae, but may be related to members of tribe Duranteae instead. Sevenclades within Citharexylum are inferred, each characterized by a combination of geography, fruit color and/or maturation, and inflorescence architecture. There is evidenceof correlated evolution between habit, axillary inflorescences, and flower number perinflorescence. Shrubs with reduced inflorescences have evolved repeatedly.Conclusions: A subgeneric classification for Citharexylum is proposed. Althoughsuites of associated traits are found, character morphology has been labile throughoutCitharexylum´s evolutionary history. Morphological diversity may be related toadaptation to differing mesic and xeric habitats.