‘Unknown yellow’: Pibiria, a new genus of Passifloraceae with a mixture of features found in Passifloroideae and Turneroideae

In 1993, a shrub with yellow flowers reminiscent of but obviously distinct from Turnera was found near Mabura Hill in central Guyana, which was recollected in 2000. This paper offers a morphological description including leaf and wood anatomy and pollen morphology in addition to a phylogenetic analysis based on plastid DNA. Thanks to these studies, the mysterious species can now be assigned a position within the larger context of Passifloraceae. Our molecular results also show that the unknown yellow', as the plant became informally known, belongs to Passifloraceae, in which it is well supported as sister to Turneroideae. It is here described as the new genus and species, Pibiria flava, and because it lacks several floral characters typically (but not universally) found in this subfamily (heterostylous, fused sepals/petals, adnation of the stamens to the calyx, presence of a corolla and clawed petals), we also propose a new subfamily, Pibirioideae, to accommodate it.