Phylogeny and the Evolution of Flower Symmetry in Posoqueria (Rubiaceae) Using the Universal Angiosperms353 Probe Set

Abstract

Posoqueria includes 15–20 species of shrubs and trees in the coffee family Rubiaceae (tribe Posoquerieae). Posoqueria is phylogenetically poorly studied and includes several taxonomic problems. Previous studies using limited molecular data and taxon sampling identified two groups within the genus based on the presence or absence of a unique, specialized pollination system known as the pollen catapult mechanism. Here, 15 Posoqueria species and two outgroups were sampled with target sequence capture, and a phylogeny of Posoqueria was generated based on 177 nuclear genes and the multispecies coalescent model. We provide phylogenomic evidence clarifying relationships among morphologically similar and taxonomically complex species ( P. grandiflora , P. longiflora , P. maxima , P. mutisii , and P. williamsii ) and our results challenge the current circumscriptions of P. chocoana , P. costaricensis , and P. latifolia s.l. The phylogenetic analysis shows that populations of P. latifolia from Central America and western Colombia represent a distinct lineage from those of the Guianas. Our phylogeny also indicates that the unique pollen catapult mechanism linked to zygomorphic flowers in Posoqueria evolved through multiple transitions and reversals, and therefore does not support splitting the genus into two groups based on this character. This novel view of the phylogenetic relationships in Posoqueria expands the horizons for future research in the group, especially from the taxonomic, evo-devo, pollination biology, ecology, and biogeography points of view.