Diversification history of Neotropical Lecythidaceae, an ecologically dominant tree family of Amazon rain forest

Abstract

The Neotropical subfamily of Lecythidaceae (Lecythidoideae) is a clade of 10 genera with an estimated number of 232 species. Lecythidaceae is the third most abundant family of trees in Amazon forests, and its most diverse genus, Eschweilera (ca. 100 species) is the most abundant genus of Amazon trees. In this chapter we explore the diversification history of the Lecythidoideae through space and time in the Neotropics. We inferred a time-calibrated phylogeny of 118 species, which we used to reconstruct the biogeographic origins of Lecythidoideae and its main clades. To test for significant changes of speciation rates in the subfamily, we performed a diversification analysis. Our analysis dated the crown clade of Lecythidoideae at 46 Ma (95% CI 1⁄4 36.5–55.9 Ma) and the stem age at 62.7 Ma (95% CI 1⁄4 56.7–68.9 Ma), suggesting dispersal from the paleotropics long after the Gondwana breakup. Most major crown clades in the Lecythidoideae (Grias, Gustavia, Eschweilera, Couroupita, Couratari, and all Lecythis and Eschweilera subclades) differentiated during the Miocene (ca. 5.3–23 Ma). The Guayana floristic region (Guiana Shield + north-central Amazon) is the inferred ancestral range for 8 out of the 18 Lecythidoideae clades (129 species, ~55%), highlighting the region’s evolutionary importance, especially for the species-rich Bertholletia clade, which includes the genera Eschweilera, Lecythis, Corythophora and Bertholletia. Our results indicate that the Bertholletia clade colonized the Trans-Andean region at least three times in the last 10 Ma. We found no significant changes in the rate of diversification inside Lecythidoideae over the Cenozoic, and found no evidence of increased speciation during the Pleistocene. Lecythidoideae has diversified not in pulses, but in a pattern of steady accumulation, akin to a museum model of diversification.