Recurrent evolutionary changes in pollen shape and ornamentation of the vataireoid clade (Papilionoideae, Fabaceae), an early-branching lineage of florally divergent genera.

This article focuses on the pollen morphology and evolutionary history of the vataireoid clade, an early-branching lineage of Neotropical trees within the Papilionoideae subfamily of Fabaceae, comprising the genera Luetzelburgia, Sweetia, Vatairea, and Vataireopsis. Using acetolysed pollen samples from 26 species analyzed by light and scanning electron microscopy, the study reveals considerable variability in pollen size, shape, aperture structure, and exine ornamentation across the clade, with multiple independent evolutionary transitions inferred over the last 16 million years. Despite this morphological diversity and evolutionary lability, certain pollen traits, such as exine ornamentation and apertural membrane type, provide taxonomic utility for distinguishing genera, although no unequivocal synapomorphies define the genera based solely on pollen characters. The findings highlight recurrent evolutionary shifts in pollen traits paralleling the floral diversity of the clade and underscore the need for broader palynological studies across early-branching papilionoid legumes to better understand pollen evolution in this diverse family.