Teucrium, Linnaeus, 1753

Juan-Pérez, Alba De, Martínez-Azorín, Mario, Crespo, Manuel B. & Alonso-Vargas, María Ángeles, 2023, First report of natural hybridisation between members of Teucrium subsect. Simplicipilosa and subsect. Polium: Teucrium × murcigerum (Lamiaceae), a new hybrid from southeastern Iberian Peninsula, Phytotaxa 584 (1), pp. 33-40 : 34-38

Teucrium × murcigerum De Juan, Mart. - Azorín, M.B.Crespo & M.Á.Alonso, nothosp. nov.

( Figs. 1B, 1D , 2B )

Type:— SPAIN. Murcia Province: Calarreona, Cuatro Calas , entre la playa de la Higuerica y la playa de La Carolina, UTM 30SXG215376, ca. 15 m elevation, 25 June 2019, M. Martínez-Azorín s.n. (ABH 82480 holo.; MA iso.).

Diagnosis:—The new nothospecies resembles T. lanigerum in general appearance, leaf and stem indumentum, shape of inflorescence, and morphology of bracteoles, but greatly differs by the smaller inflorescence (head 1–1.5 mm long); floral bracteoles as long as flowers, the lowermost almost sessile; calyx smaller (3–4 mm long), with indumentum of simple shorter hairs (0.5–1 mm long), three of the five teeth ending into a narrow, curved hook-like extension ca. 0.5 mm long; corolla not uniformly purplish, the central lobe smaller (1–1.5 mm long), cream coloured in the central part; and the posterior lateral lobes of corolla with scarce simple shorter (0.5 mm long) hairs. The new hybrid also approaches T. murcicum in morphology and size of the calyx and lobes of the corolla, and the features of floral bracts and bracteoles, but markedly differs from the latter species in the general appearance (much resembling T. lanigerum ), and also the entire absence of coralliform hairs in all parts, and the reddish-colour of the corolla lobes.

Description:—Suffruticose cushion-like, half-shrub to 20 cm high. Stems suberect, quadrangular in section, all bearing decussate, spaced leaves; the winter-spring stems whitish-greyish with abundant curly, simple hairs 0.5–0.8 mm long; the flowering stems (1.5) 2–5.5 cm long, ascending, reddish, with scarce curly simple hairs 0.4–0.6 mm long. Leaves (4)6–10 × 1 mm, opposite, decussate, patent to suberect, linear-oblong, with revolute margins, crenate from the basal third or the middle with 5–7 lobe pairs; adaxial side greenish, with wavy or curly simple hairs 0.4–1 mm long; abaxial side whitish, with abundant wavy simple hairs 0.5–0.8 mm long. Inflorescence a terminal subglobose, dense head, 1–1.5 × 0.9–1.3 cm, sometimes with two lateral smaller basal heads of 0.8–1 × 0.8–0.9 cm, rarely presenting smaller inflorescences on the lower 1 or 2 pairs of leaves, which are sessile o rarely shortly pedunculate. Bracts 4–6 × 0.9–1.1 mm, oblong-linear, with revolute margin, sometimes crenate along the distal portion, with scarce simple hairs on the abaxial side. Basal bracteoles 4–5 × 0.5–1 mm, oblong-lanceolate with revolute margins, about as long as flowers, with scarce simple hairs 0.5–1 mm long, with an almost indistinguishable petiole. Upper bracteoles 5–6 × 0.5–1 mm, as long as flowers, lanceolate-linear revolute on margins, with scarce simple hairs 0.5–1 mm long, with petiole 1–2 mm long. Calyx greenish-reddish, 3–4 × 2–3 mm, tubular-campanulate, with wavy simple hairs 0.7–0.8 mm long externally and on the margin of teeth; tube 2–2.5 × 2 mm; teeth five, two widely triangular 1–1.5 × 1 mm and three narrowly triangular ending into a narrow, curved, hook-shaped extension (cuculla). Corolla unilabiate, mostly purplish with cream coloured central lobe, 4–5 mm long, with a narrow tube ca. 2 mm long enclosed into the calyx, with glandular hairs on the outer side covering mostly the central lobe, with scarce simple hairs 0.5–1 mm long on the inner side; posterior lateral lobes 1.3–1.4 × 1 mm, with scarce simple hairs ca. 0.5 mm long; lateral lobes 1 × 0.3–0.5 mm, ovate; central lobe 1–1.5 × 1 mm, subauriculate. Fruit schizocarpous, enclosed into the calyx, producing 4 subovoid nuculae, commonly not all developed, which are ca. 1.5 mm long, dark brown to black, with grooved surface resembling T. murcicum but with less distance among grooves.

Etymology:—Named after the combination of the two parental names, ‘ murci-cum ’ and ‘ lani-gerum ’ (murcigerum).

Phenology:— Teucrium × murcigerum flowers around June, when the two parental species, T. murcicum and T. lanigerum , are also in flower at the type locality near Calarreona , Murcia province, Spain.

Habitat and distribution:—The new nothospecies is currently known from a single established plant growing at the type locality, south of Calarreona, where T. lanigerum and T. murcicum occur in the near vicinity ( Fig. 1 ). The specimen, morphologically intermediate between both putative parentals, was found beside a mature plant of T. lanigerum ( Fig. 1 ) and with several individuals of the latter species in a south-facing exposition, which would agree with the maternal inheritance of T. lanigerum in the new nothospecies. The nearby population of T. murcicum was found about 50 m to the north from the cited T. lanigerum population on a north-facing slope. They all occur in open low shrubland on carbonated soils of bioclimatically Inframediterranean Semiarid sites (according to RivasMartínez 2007), together with Anthyllis cytisoides L., Anthyllis terniflora (Lag.) Pau , Asteriscus maritimus (L.) Less., Cistus albidus L., Fumana ericoides (Cav.) Gand. , Genista umbellata (L’Hér.) Poir. subsp. umbellata , Helianthemum fontqueri Sennen , H. syriacum (Jacq.) Dum. -Cours., Launaea lanifera Pau , Limonium insigne (Coss.) Kuntze , Periploca laevigata subsp. angustifolia (Labill.) Markgr. , Rosmarinus officinalis L., Sideritis ibanyezii Pau , Teucrium capitatum L. subsp. gracillimum (Rouy) Valdés Berm. , and Thymus hyemalis Lange , among others. They participate in low shrublands belonging to the phytosociological association Teucrio lanigeri-Sideritidetum ibanyezii Rivas Goday & Esteve 1968 corr. Alcaraz, T.E. Díaz, Rivas-Martínez & P. Sánchez 1989 (see Alcaraz et al. 2009).

Diagnostic characters and taxonomic relationships:— Teucrium × murcigerum constitutes the first record of natural intersubsectional hybridisation between T. subsect. Polium ( T. murcicum ) and subsect. Simplicipilosa ( T. lanigerum ). This new nothospecies resembles T. lanigerum in overall morphology, and shows the simple, wavy-curly hairs of the latter species, agreeing with the most probable maternal inheritance of the hybrid. The new nothospecies however, shows intermediate characters between the two parentals T. murcicum and T. lanigerum ( Table 1 , Figs. 1–2 ), such as the stems, leaves or bracteoles that show the typical simple wavy hairs of T. lanigerum , though with lower density or length; the inflorescence and bracteoles length approaching T. murcicum , with bracteole petioles showing intermediate sizes; the calyx being clearly shorter than both parentals, morphologically similar to that in T. lanigerum but with much shorter hairs and tube and teeth morphology approaching T. murcicum ; the corolla being shorter than in both parental species, mostly purplish, as in T. lanigerum , though the central lobe cream-coloured that shows glandular hairs only on the central lobe, like in T. murcicum ; the posterior lateral lobes with simple hairs, like in T. lanigerum , but with a considerably lower density and shorter hairs, since the lobes in T. murcicum are glabrous; and the nucule shows the size of T. lanigerum but the ornamentation of T. murcicum , though with smaller grooves ( Table 1 , Fig. 2 ). The hybrid nature is sufficiently justified on morphological grounds. Furthermore, both parentals show the same chromosome number (2 n = 26), which apparently makes hybridisation processes easier between both species.

Other Iberian hybrids have been reported with T. lanigerum or T. murcicum acting as parental species (Lahora Cano & Sánchez Gómez 2010, Sánchez Gómez et al. 1999, Sánchez Gomez & Navarro 1999), where the resulting segregated characters agree with those defining Teucrium × murcigerum. For instance, the hybrid Teucrium × motae Lahora & Sánchez Gómez (2010: 205) ( T. carolipaui Vicioso ex Pau subsp. fontqueri (Sennen) Rivas Mart. × T. murcicum ) shows the indumentum of T. carolipaui Vicioso ex Pau (1922: 185) subsp. fontqueri ( Sennen 1932: 102) Rivas Martínez (1974: 88) in some parts and lacks the coralliform hairs typical of T. murcicum , though retaining the corolla and leaf size, and calyx morphology of the latter species ( Lahora & Sánchez Gómez 2010). Similarly, in Teucrium × guemesii J.F.Jiménez et al. (in Sánchez-Gómez et al. 1999: 205) ( T. carolipaui subsp. fontqueri × T. lanigerum ) and in T. × eloualidii Sánchez Gomez & Navarro (1999: 167) ( T. lanigerum × T. freynii E.Rev ex Willkomm 1893: 159 ), the indumentum is closer to T. lanigerum but with less general density, as it also occurs in the newly described Teucrium × murcigerum. However, in both latter cases both parentals belong to simple-haired sections or subsections and entirely lack coralliform indumentum.

As in the case of Teucrium × motae , the indumentum displayed by hybrids between species of T. subsect. Polium and those of simple-haired groups (e.g., T. subsect. Simplicipilosa, subsect. Pumila or T. sect. Montana Lázaro Ibiza 1896: 776 ) shows some common features. For instance, in Teucrium × mateoi Solanas et al. (1993: 80) ( T. carolipaui subsp. carolipaui × T. ronnigeri Sennen 1931: 47 ) and T. × alrumanae M.B.Crespo & J.C.Cristóbal (2017: 5) ( T. ronnigeri × T. thymifolium Schreber 1773: 50 ), the hybrids completely lack coralliform hairs, as it occurs in the newly described hybrid, or at most they are replaced by weakly branched trichomes intermingled with the dominant simple hairs. This appears to point out to the fact that the coralliform indumentum tends to be displaced by the simple (or weakly branched) trichomes after hybridisation. The discovery of new hybrids affecting those groups will help to test that hypothesis.

Additional material studied:

Teucrium lanigerum :— SPAIN. Murcia Province: Calarreona, Cuatro Calas , entre la playa de la Higuerica y la playa de La Carolina, 30SXG215376, ca. 15 m elevation, 25 June 2019, M. Martínez-Azorín s.n. (ABH 82478!); Cabo Cope, 30SXG3444, 15 m elevation, 5 May 1997, M.A. Carrasco & E. Pangua s.n. (ABH 37382!); Águilas, 30SXG2138, 18 m elevation, 26 May 1991, M.D. Lledó & M.B. Crespo s.n. (ABH 646!); Águilas, 30SXG 1439, 280 m elevation, 26 May 1991, M.D. Lledó & M.B. Crespo s.n. (ABH 649!).

Teucrium murcicum :— SPAIN. Alicante Province: Guardamar del Segura, Playa del Moncayo, YH0615, 4 m of elevation, 28 February 1998, A. Ruiz de León & J.C. Cristóbal s.n. (ABH 39067!). Almeria Province: Roquetas de Mar, 1 km to Punta El Sabinar, WF2661, 5 m of elevation, 11 April 1998, M.B. Crespo, A. Juan & J.C. Cristóbal s.n. (ABH 34056!); Cabo de Gata, Salinas de Cabo de Gata, 30SWF7075, 31 March 1997, M.Á. Alonso & J.J. Montoya s.n. (ABH 42501!). Murcia Province: Calarreona, Cuatro Calas, entre la playa de la Higuerica y la playa de La Carolina, 30SXG215377, ca. 10 m of elevation, 25 June 2019, M. Martínez-Azorín s.n. (ABH 82479!); Cieza, Sierra del Oro, 30SXH 33, 550 m elevation, 15 May 1979, E. Valdés Bermejo, S. Castroviejo, S. Cirujano & P. Coello, 5165EV (ABH 79863!).

Figures

FIGURE 1. Habitus and inflorescence details of parental and hybrid Teucrium taxa. A. Teucrium lanigerum; B. Teucrium × murcigerum; C. Teucrium murcicum; D. Detail of Teucrium × murcigerum. All from the type locality near Calarreona, Murcia Province, Spain.

FIGURE 2. Flower and fruit morphology of parental and hybrid Teucrium taxa. A. Teucrium lanigerum; B. Teucrium × murcigerum; C. Teucrium murcicum; 1. Flower in lateral view; 2. Flower in dorsal view; 3. Flower in ventral view; 4. Corolla in lateral view; 5. Dissected calyx (outer side); 6. Fruits.