Morphology and character evolution of seedlings in Leptolobieae (Leguminosae, Papilionoideae)

Molecular phylogenetic evidence demonstrate the monophyly of five genera ( Bowdichia, Diplotropis, Guianodendr on, Leptolobium and Staminodianthus ) into a recircumscribed Leptolobieae. Even though recognition of the tribe is highly supported by molecular data, morphological characterization of its taxa is still challenging. In this context, our study aimed to study the seedling morphology of eleven species from all genera of Leptolobieae. The seedling morphology of Staminodianthus racemosus is here described for the first time. The observed characters were scored into a morphological matrix and mapped onto a phylogeny in order to detect potential synapomorphies for major clades. Three morphological types of seedlings were observed and described: phanero-epigeo-foliaceous seedlings (PEF) in Bowdichia virgilioides and Leptolobium spp., crypto-hipogeo-reserve seedlings (CHR) in Guianodendron praeclarum and Diplotropis martiusii, and phanero-hipogeo-reserve seedlings (PHR) in S. racemosu s. PEF morphotype was reconstructed as the mostly likely state in the most recent common ancestor (MRCA) of Leptolobieae, with subsequent transitions to the CHR morphotype in Diplotropus and Guianodendron , and to the PHR morphotype in S. racemosus . Another five seedling characters were reconstructed as potential synapomorphies for clades in Leptolobieae: hypocotyl shape and length, epicotyl length, presence of glands at the eophyl axyl and the number of leaflets at the seedling first node. For Leptolobium , the phyllotaxy, number of eophylls from first to third node, leaflet shape, apex and base form, and the presence of stipels are diagnostic characters within species and could be used for taxonomic purposes.