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Carlos collecting Quercus ×alentejana (Q. faginea × Q. pyrenaica) in northeastern Portugal for his PhD thesis © Carlos Vila-Viçosa
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Plant Focus

Quercus crassipes acorns with inrolled cupule margin
One of the more well-known Mexican oaks in cultivation.

Updated Classification of Oaks: a Summary

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Béatrice Chassé

Published May 2018 in International Oaks No. 29: 11–18.


The recently published updated infrageneric classification of the genus Quercus (Denk et al. 2017)1 based on molecular phylogeny and pollen ornamentation confirms that the traditional subgeneric division between, on the one hand, Cyclobalanopsis (the East Asian subtropical and tropical oaks), and, on the other, Quercus (all other oaks) is artificial. This present paper gives an overview of past classification systems, the basis upon which current oak phylogeny has been constructed, and of the perspectives for future research as regards the morphological circumscription of infrasectional groups.

1 An electronic appendix can be retrieved at https://doi.org/10.6084/m9.figshare.5547622.v1 and includes the following valuable information (which may be subject to future updates): (i) an overview of earlier systematic schemes for oaks (genera, subgenera, sections) in comparison to the new classification; (ii) diagnostic morphological traits reported by earlier taxonomists extracted from the original literature; (iii) a comprehensive list of formerly and currently accepted species of oaks, compiled from the cited oak monographs and complemented by further data sources.


Quercus agrifolia, Quercus chrysolepis, Quercus douglasii, Quercus engelmannii, Quercus garryana, Quercus kelloggii, Quercus lobata, Quercus wislizeni


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