Master's thesis: PHYLOGENY AND EVOLUTION OF FLOWER SYMMETRY OF POSOQUERIA (RUBIACEAE)

The genus Posoqueria is a Neotropical group of shrubs and trees in the coffee family Rubiaceae, which is phylogenetically poorly understood and presents several internal taxonomical difficulties. Previous molecular studies using limited loci and taxa suggest the species in Posoqueria could be split in two monophyletic groups based on the presence and absence of a unique specialized pollination system known as the Pollen Catapult Mechanism (PCM), which would imply the resurrection of the genus Stannia. Here, I used samples from 15 species and a high-throughput sequencing strategy to target-capture 353 nuclear loci, from which 177 genes were chosen to generate a phylogeny of Posoqueria using the multispecies coalescent (MSC) method. The study confirms the monophyly of most Posoqueria taxa, provides evidence of the phylogenomic distinctiveness of species such as P. mutisii, P. longiflora, P. maxima, P. grandiflora, and P. williamsii, and questions the current circumscription of P. chocoana and P. costaricensis. Particularly, the phylogeny supports the re-circumscription of P. latifolia, suggesting that populations from Central America and Colombia belong to an undescribed species in the genus. This phylogenomic study indicates that flower symmetry and the unique catapult mechanism linked to zygomorphic flowers in Posoqueria is the product of several evolutionary transitions and is therefore non-monophyletic. These results challenge the hypothesis that this trait played a significant role in the diversification of the genus and put an end to a long-standing debate about the taxonomy of Posoqueria and its synonym Stannia, dating back to the 1850s, by showing that resurrecting Stannia as a valid taxon is not justified. However, some phylogenetic relationships were recovered with moderate to weak support, requiring further investigation that could include designing a customized bait panel that allows to resolve recent diversification events in Posoqueria