Assembling the Neotropical Tree Flora: Andean Uplift and the Historical Biogeography of the Brazil Nut Family (Lecythidaceae)

ABSTRACT Aim The assembly of tropical tree floras is complex, involving many lineage‐specific histories; however, focusing on the biogeographic history of diverse clades can reveal general patterns. We investigated the historical biogeography of the ecologically important Brazil nut clade (Lecythidoideae) to: (1) expand prior phylogenies with greater sampling of the early branching Andean‐centered subclades; (2) infer the ages and dispersal histories of the major subclades; and (3) document instances of niche evolution within Lecythidoideae, with an emphasis on elevational range shifts. Location Tropical America. Taxon The Neotropical subfamily Lecythidoideae (Lecythidaceae). Methods We expanded phylogenetic taxon sampling to 371 samples representing 197 species across bioregions, emphasizing the Andean‐centered genera Grias and Gustavia . A maximum likelihood phylogeny was inferred using 665 nuclear loci, and divergence times were estimated with four fossil constraints. Ancestral ranges were reconstructed across bioregions and ecoregions using three biogeographic models. Results The crown age of Lecythidaceae is placed in the mid‐Cretaceous (~94 Ma) and the Neotropical clade Lecythidoideae in the Eocene (~51.5 Ma). Grias likely originated in Central America or the Pacific coastal forests of South America (~35.5 Ma), Gustavia in the Amazonian moist forests (~36 Ma) and the Bertholletia clade in Western‐Central Amazonia (~20 Ma). Following geographic dispersal from eastern and western sources, Grias , Gustavia and Lecythis diversified along the Andean slopes; Scottmoria in Central America, and Imbiriba in the Atlantic Forest. Main Conclusions Most Lecythidoideae subclades diversified during the Miocene, a period of major landscape change associated with the tectonic activities that generated the Northern Andes, the formation of the Amazon drainage system and the closure of the Isthmus of Panama. While most species retained lowland rainforest niches, several lineages shifted into Andean montane forests, highlighting how geological change and ecological transitions shaped the assembly of Neotropical tree floras.