Abstract

Premise of research. Mammea (Calophyllaceae) is a pantropical genus of 70 tree species, most of which are native to Madagascar. We describe a new species of Mammea on the basis of a fossil stem from the lower Miocene of Panama, discuss its implications for the biogeography of the genus, and assemble a set of morphological characters to examine the phylogeny of Calophyllaceae and confirm our identification.

Methodology. We prepared the fossil stem using the cellulose acetate peel technique and compared its anatomy with that of extant plants, including a specimen of Mammea americana obtained from Puerto Rico, and with that of other fossils. For our phylogenetic analysis, we modified a previously published morphological matrix of reproductive and vegetative characters and added 14 wood characters, for a total of 66 characters.

Pivotal results. Distinctive anatomical features of Mammea paramericana sp. nov. include predominantly solitary vessels, vasicentric tracheids, fibers with distinctly bordered pits in both radial and tangential walls, diffuse-in-aggregates axial parenchyma, narrow rays with upright marginal cells, and radial canals. The fossil stem has shorter pith cells, wider vessels, and fewer rows of upright marginal ray cells, and it lacks scalariform perforation plates compared with the sample of extant M. americana from Puerto Rico. The close relationship between the fossil and modern Mammea is supported by all of the most parsimonious trees from the phylogenetic analysis, as is the monophyly of Calophyllaceae.

Conclusions. This fossil is the earliest evidence of Mammea in the Neotropics and is roughly coeval with previously recognized fossils of the genus from Africa. The fossil demonstrates that the diversification of Mammea in the Americas was underway by 19 Ma. Mammea likely reached the Neotropics from Africa via long-distance dispersal. While the morphological phylogenetic analysis recovers some of the relationships found in molecular topologies, it remains unresolved with respect to the immediate relatives of Mammea.