Quercus × gaonae Vila-Viçosa, Frias & F.M. Vázquez, 2024

Vila-Viçosa, Carlos, Frias, Iúri & Vázquez, Francisco, 2024, Finding the last missing white oak hybrid from the Iberian Peninsula (Fagaceae, Quercus, sect. Quercus), Phytotaxa 641 (3), pp. 183-190 : 185-187

Quercus × gaonae Vila-Viçosa, Frias & F.M. Vázquez nothosp. nov. (Figs. 2,3,4 and 5)

Quercus canariensis Willd. × Quercus lusitanica Lam.

Type:— SPAIN. Andalusia: Cádiz, Parque Natural de los Alcornocales , Sierra del Bujeo , Ascent to Llanos del Juncal , 36.095 457, - 5.534 832, 650 m, 09 August 2023, Carlos Vila-Viçosa, Iúri Frias & José Gaona Ríos s.n. (Holotype: PO V 72216 ( Fig. 3 ), Isotypes: HSS 87103 ; LISE 96338 ) .

Diagnosis: Q. ×gaonae is distinguished from both parents by possessing intermediate characters, such as leaves having the proximal third with entire margins, as in Q. lusitanica , with larger, lanceolate to rhomboidal leaves with serrate margins and some deep lobes and divaricate secondary nerves, as in Q. canariensis ( Figs. 3 and 4 ). In addition to the stellate and multistellate trichomes that are characteristic of Q. lusitanica , it also has the deciduous, fuzzy and cottonlike yellowish tomentum, composed of fasciculate trichomes, typical of Q. canariensis , on the midrib and axillary veins ( Fig. 5 ).

Description: Prostrate to erect shrub up to 150 cm tall, intermediate between the parents ( Figure 2 ). Leaves with ovate-obovate to lanceolate and sometimes rhomboidal, blade (3)4–7(8) × (1.5) 2–4(5) cm. Most leaves with entire margin in the proximal third, the second and distal thirds serrate to dentate, sometimes deeply lobed, and a 3–9 mm short and pubescent petiole. Glabrescent adaxial leaf surface, with sparse stellate, multi-stellate, and simple trichomes on the midrib and the proximal half of the leaf. Abaxial leaf surface pubescent, covered with single, stellate, and multi-stellate trichomes, plus the presence of a deciduous fuzzy fasciculate and yellowish tomentum on the midrib, more prominent at the leaf base and the intersection of the secondary nerves with the midrib. Secondary veins often divaricate towards the lobes with irregular shape and, as in Quercus canariensis , producing several leaves with deep lobes and very irregular margins.

Etymology: Dedicated to the eminent Gaditan naturalist and friend José Manuel Gaona Ríos (1971).

Figures

FIGURE 2. Type location of Quercus ×gaonae (middle—red oval), developing conspicuously erect shoots, among the parents, the prostrate Q. lusitanica (left—turquoise oval) and growing below the Q. canariensis arboreal layer (above—green oval).

FIGURE 3. Holotype of Quercus ×gaonae Vila-Viçosa, Frias & F.M. Vázquez PO V72216! (Porto University, Natural History and Science Museum).

FIGURE 4. Abnormal leaf shapes of Q. ×gaonae, some with the proximal half of the leaf entire, as in Q. lusitanica and simultaneously with serrate margins, possessing deep lobes and divaricate secondary nerves, showing the influence of Q. canariensis, and indicating hybridization between these taxa.

FIGURE 5.Indumentum details of Q.×gaonae:60×, 100× and160×, yellowish fuzzy indumentum deriving fromthe parent Q. canariensis on the midrib and axillary veins; 200×, dominance of stellate and multistellate trichomes, deriving from the parent Q. lusitanica, on the abaxial leaf surface.