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Plant Focus

Quercus macdougallii
A rare oak endemic to the Sierra Juárez in Oaxaca

Systematics and Biogeography of the American Oaks

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Paul Manos

Published May 2016 in International Oaks No. 27: 23–36


The major groups of American oaks will be discussed with reference to phylogenetic patterns and newly resolved species alliances within the sections Quercus (White Oaks) and Lobatae (Red Oaks). Recent analyses of the nuclear genome based on extensive sampling across approximately 150 species suggest that oak species are mostly cohesive and compose geographically defined morphological groups. However, compelling evidence has been detected for ancient and current hybridization within section Quercus. Genomic data confirm our expectations when localized hybridization is suspected based on morphology and geographic proximity, but these data also point to more cryptic scenarios involving historic interbreeding among geographically disjunct and distantly related species. The biogeographical history of section Quercus in the Americas is highlighted by two independent intercontinental disjunctions, with the Eurasian species Quercus pontica to the Roburoid group. Within the Americas, sections Quercus and Lobatae share strikingly similar biogeographic histories, supporting originations and deeper evolutionary splits at higher latitudes, followed by more recent parallel dispersals and diversifications south to Mexico and Central America.


phylogeny, Quercus, Lobatae, Protobalanus, Virentes, Ponticae


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