Taxonomic significance of pollen ornamentation in the Hymenaea clade (Leguminosae, Detarioideae)

Abstract

Detarioideae is one of the most florally diverse legume lineages, in which the 84 genera and ca. 760 species variously interact with pollinating bees, bats, and birds. However, pollen ornamentation has not been extensively studied in the subfamily. Here we focus on describing the morphological variation of pollen ornamentation in the Hymenaea clade, a small lineage comprised of ca. 65 species in the florally heterogeneous genera Guibourtia, Hymenaea, and Peltogyne. We analyzed pollen grains of 32 taxa using scanning electron microscopy to characterize and illustrate their exine ornamentation. We show that pollen traits have high taxonomic significance within the Hymenaea clade. We hypothesize that highly specialized interactions with pollinating organisms might have shaped not just distinct floral architectures within the Hymenaea clade but also its highly variable pollen ornamentation.