PHYTOGEOGRAPHIC HISTORY OF THE HUMIRIACEAE (PART 2).

Premise of research. Humiriaceae occupy predominantly Neotropical lowland rainforests, with only a single Old World species in western Africa. Molecular divergence time estimates suggest that the family might have originated during the middle Cretaceous; however, fossil occurrences are lacking prior to the Paleocene. Here we provide new fossil evidence that expands our understanding of the paleobiogeographic history and evolution of this family. Methodology. Fossil endocarps and wood were compared with extant relatives of the family. Transverse and longitudinal sections of fossil and modern fruits were studied anatomically and morphologically. Pivotal results. Fruits of the new species, Duckesia berryi sp. n., from the Oligocene of Pacific coastal Peru (ca. 30-28.5 Ma), provide the earliest fossil evidence of Duckesia--the genus is now confined to Amazonia. We also document the earliest fossil fruit record for Sacoglottis tertiaria, from the early Oligocene (ca. 33.9-28.4 Ma) of Puerto Rico, and a new occurrence of Vantanea cipaconensis fruits, from the late Miocene of Panama (ca. 9-8.5 Ma). The new fossil wood, Humiriaceoxylon ocuensis gen. et. sp. n., from the late Eocene (ca. 37.2-33.9 Ma) of Ocú, Panama, confirms that this family was represented by large trees anatomically consistent with the extant genera. Conclusions. Humiriaceae originated in the Neotropics, with the oldest-known occurrences being fruits of Lacunofructus cuatrecasana and wood of H. ocuensis from the late Eocene of Panama. The family was generically diverse and widely distributed geographically across northern South America and Central America by the early Miocene. The new fossils also provide further evidence of regional extinctions within the Neotropics; extirpation of particular genera from Central America, the Caribbean, and coastal Peru indicate that Neogene orogenic and climatic events had an important effect on the modern-day distribution of the family. [ABSTRACT FROM AUTHOR]