Phylogeny and historical biogeography of the Neotropical palm tribe Euterpeae (Arecaceae)

Pichardo Marcano, Fritz J. (2018) Phylogeny and historical biogeography of the Neotropical palm tribe Euterpeae (Arecaceae). Masters thesis, Memorial University of Newfoundland.

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Abstract

Tribe Euterpeae is a group of Neotropical palms that comprises 33 species in 5 genera distributed from Central America to Southeastern Brazil and Bolivia, including the Caribbean islands. Some species are important elements of Amazonian forests since they can be among the 10 most abundant trees. Some members of this tribe are economically important for their oil production and edible palm heart. In this study I aimed to clarify the intergeneric and interspecific relationships within Euterpeae and estimate the time and place of origin of its taxa. I also tested for changes in inflorescence types in the tribe. I reconstructed a phylogenetic tree with maximum likelihood and a dated Bayesian phylogenetic tree using one plastid (trnD-trnT) and four low-copy nuclear DNA regions (CISP4, WRKY6, RPB2, and PHYB). I used five fossil and two secondary calibration points to estimate divergence times. I amplified sequences from 27 Euterpeae species including 7 infra-specific taxa and 41 outgroup taxa. The tribe and each genus were monophyletic with high support. Hyospathe was sister to the rest of the genera. Euterpe was sister to Neonicholsonia and Prestoea was sister to Oenocarpus. The ancestral inflorescence type of Euterpeae is likely one with rachillae all around the main axis from which the hippuriform (horsetail shape) inflorescence of Oenocarpus originated. Some widely distributed species with infra-specific taxa (Euterpe precatoria, Prestoea acuminata and Hyospathe elegans) were not monophyletic, which invites a revision of these species circumscriptions. The Euterpeae diverged from its sister clade Areceae at around 46 million years ago (Mya), while the crown age of the Euterpeae was estimated at around 40 Mya. Although Euterpeae’s origin occurred in the Eocene most of the extant genera had crown ages after the middle Miocene (<17 Mya) with some species originating later during the Pliocene to Pleistocene. This work represents the most complete molecular phylogeny of the group, and inclusion of the few missing narrow endemic taxa will provide a more complete understanding of the interspecific relationships of the tribe.

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