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Plant Focus

Quercus xjackiana acorns
The hybrid of Q. alba and Q. bicolor

The New Annotated Checklist of the Portuguese Oaks

During a PhD project to resolve the Iberian White Oaks (section Quercus) phylogenetic backbone at BIOPOLIS, there arose the need to solve the simmering nomenclatural conundrum around genus Quercus in the Western Mediterranean. The early stages involved the gall oaks, which have been traditionally treated as subsection Galliferae in section Quercus. The cascade of names applied to this group of oaks, inflated by introgression, caused many uncertainties; a congruent study and analysis of type materials was lacking, as was comparative molecular analysis in wild populations.

The analysis of the Iberian gall oaks and their hybrids allowed a broader overview of most of the White Oaks from southwest Europe, especially since Q. faginea makes hybrid swarms with most of the remaining White Oaks. The molecular data, retrieved from samples collected in historical sites and type locations for each taxon or nothotaxon, represented very important contributions in the Western Mediterranean scenario. For instance, it solved infrasectional dichotomy among the White Oaks of the Western Palearctic (Europe and Africa north of the Sahara), separating the species inside broad Q. petraea and broad Q. robur from the sub-Mediterranean and typically marcescent species that encompassed what was previously known as section Dascia and section Galliferae. These subsections were proposed and formalized as subsection Hartwissianae and Macrantherae, with elected type species (Q. hartwissiana and Q. macranthera). Among the Iberian Roburoid oaks that exist in Portugal, Q. estremadurensis and Q. orocantabrica (Q. robur subsp. broteroana) were recovered as distinct from the European pedunculate oak (Q. robur L. sensu stricto), while Q. faginea (Portuguese Oak) was restricted to a single species with no subspecies.

The kermes oaks were also deeply analyzed, and ambiguity surrounding the Western Mediterranean downy kermes oaks was solved; Q. airensis was selected as the next available name for the original concept of Q. calliprinos (the name Q. calliprinos Webb should be conserved with a conserved type, as it has for many years been commonly regarded as the correct name for the arboreal kermes oak of the Eastern Mediterranean); the arboreal Q. pseudococcifera, which occurs in the fringes of Q. canariensis and Q. faginea forests, was also recovered as a species.

Quercus xalvesii
The newly named Quercus ×alvesii (Q. lusitanica × Q. rotundifolia) at the Botanical Garden of the Universidad do Porto © Teresa Fernandes

Apart from expanding the number of species within the national territory from eight to eleven, the list of hybrids includes a total of 23 nothotaxa, including five new names: Q. ×alvesii (the natural hybrid between Q. lusitanica and Q. rotundifolia, growing in the living collection of the University of Porto Botanical Garden), Q. ×almeidae (Q. pseudococcifera × Q. rotundifolia), Q. ×capeloana (Q. pseudococcifera × Q. suber), Q. ×eborense (Q. coccifera × Q. rotundifolia), and Q. ×sampaioana (Q. lusitanica × Q. estremadurensis), the last being dedicated to the renowned botanist Gonçalo Sampaio, who made important contributions to the nomenclature of Iberian oaks; type specimens for the new names are deposited in the Herbarium of the University of Porto (PO).

Quercus xalvesii type specimen
Holotype of Quercus ×alvesii  © Porto University, Natural History and Science Museum​​​​​​

The Checklist, co-authored by Carlos Martins Vila-Viçosa, Jorge Capelo, Paulo Alves, Rubim Almeida and Francisco María Vázquez, is available for download here.

Further reading

Denk, T., G.W. Grimm, P.S. Manos, M. Deng and A.L. Hipp. 2017. An updated infrageneric classification of the oaks: review of previous taxonomic schemes and synthesis of evolutionary patterns. Oaks physiological ecology. Exploring the functional diversity of genus Quercus L.: 13–38.

Desfontaines, R. 1799. Flora Atlantica, sive Historia Plantarum, quae in Atlante, Agro tunetano et algeriensi crescunt: Panckouckes.

Gürke, M. 1897. Quercus. In: Richter K ed. Plantae Europaeae [Enumeratio systematica et synonymica plantarum phanerogamicarum in Europa sponte crescentium vel mere inquilinarum]. Leipzig: Engelmann, 54–72.

Rivas-Martínez, S., T.E. González-Días, F.F. González, J.J. Loidi, M.F. Lousã, Á.P. Merino. 2002. Vascular plant communities of Spain and Portugal: addenda to the syntaxonomical checklist of 2001. Part II. Itinera Geobotanica(15): 433–922.

Schwarz, O. 1936. Entwurf zu einem natürlichen System der Cupuliferen und der Gattung Quercus L. Notizblatt des Botanischen Gartens und Museums zu Berlin-Dahlem: 1-22.

Schwarz, O. 1937. Monographie der Eichen Europas und des Mittelmeergebietes. Repertorium novarum speciarum regni vegetabilis 1: 1–200.

Spach, É. 1842. Histoire naturelle des végétaux: Phanérogames. Vol. 11. Librairie encyclopédique de Roret, Paris. Paris.

Vasconcellos, J.C., J.A. Franco. 1954. Os Carvalhos de Portugal. Anais do Instituto Superior de Agronomia 21: 1–135.

Vázquez, F.M., A. Coombes, R. Almeida, D. Garcia-Alonso, F. Marquez-García, C. Vila-Viçosa. 2020. Lectotypification of names of Quercus spp.(Fagaceae) described by Lamarck from the Iberian Peninsula. Phytotaxa 455(3): 205–213.

Vázquez Pardo, F.M., A.J. Coombes, D. García Alonso, F. Márquez García, C. Rodrigues Meireles, M.J. Guerra Barrena and C. Vila-Viçosa. 2018. Anotaciones a la nomenclatura del género Quercus L., (FAGACEAE) en la Península Ibérica y NW de África. Folia Botánica Extremadurensis 12: 5–79.

Vila-Viçosa, C., R. Arraiano-Castilho, A. Hipp, F.M. Vázquez, R. Almeida, C. García, A. Beja-Pereira, H. Azevedo. 2021. RAD-Seq unveils the phylogenetic backbone of the Iberian white oak (Quercus L. section Quercus) syngameon.In Pérez Badia RM, J.C. . First Spanish Botanical Society Congress (SEBOT). Sociedad Española de Botanica. Toledo. 175.

Vila-Viçosa, C., T. Matos Fernandes, J. Moreira, J. Junqueira, J. Tinoco, I. Frias, P. Farinha-Marques P. 2022. Developing the Oak Collection at the Jardim Botânico da Universidade do Porto (Portugal). International Oaks 33: 159–172.

Vila-Viçosa, C., J. Gonçalves, J. Honrado, Â. Lomba, R.S. Almeida, F.M. Vázquez, C. Garcia. 2020. Late Quaternary range shifts of marcescent oaks unveil the dynamics of a major biogeographic transition in southern Europe. Scientific reports 10(1): 1–12.

Webb, P. 1838. Iter Hispaniense. Paris: Béthune and Plon.