Genista nuragica Bacchetta, Brullo & Giusso, 2020

Bacchetta, Gianluigi, Brullo, Salvatore, Chiapella, Laura Feoli, Velari, Tiziana Cusma, Fenu, Giuseppe & Galdo, Gianpietro Giusso Del, 2020, Taxonomic remarks on Genista salzmannii group (Fabaceae) in Sardinia and Corsica, Phytotaxa 449 (1), pp. 31-51 : 32-35

Genista nuragica Bacchetta, Brullo & Giusso , sp. nov., Fig. 2

Type:— ITALY. Sardinia: Margiani Pubusa (Montarbu), Seui ( OG), 26 May 2002, G. Bacchetta, S. Brullo, M. Casti & G. Giusso s.n. (holotype CAT!; isotypes CAG!, CAT!) .

Haec species a Genista desoleana habitu pulvinato-prostrato, minore, bracteolis lineari-subulatis, brevioribus, pedicello subequalibus vel brevioribus, calyce breviore,, pilis brevioribus, labio inferiore longiore, dente centrali lineari-subulato, longiore, dentibus lateralibus longioribus, labio superiore basi angustiore, vexillo ad apicem truncato, longiore, carina longiore, antheris rotundatis apice, brevioribus, legumine breviore, 2–4 spermo, seminibus minoribus.

Dwarf shrub, pulvinate-prostrate, robust, compact, 10–30 cm tall, with branches rigid, with spiny apex, striate, sericeous (juvenile), glabrous at maturity. Leaves 1-foliate, sessile, linear-lanceolate, sericeous, 2–6 mm, caducous. Inflorescences few-flowered. Bracts lanceolate, canaliculate, 3–4.5 mm, longer than the pedicel. Bracteoles linear-subulate, apiculate, 1.2–1.6 mm, shorter or subequal to the pedicel, inserted at the low half part of the pedicel. Pedicel 2–3 mm. Calyx sericeous whit hairs 0.1–0.2 mm long, conic-campanulate, 7–8 mm, with veins incrassate and decurrent only in the lips; lower lip 4.5–5 mm with teeth 1-nerved, the central tooth linear subulate, 1.8–2.5 mm long and longer than lateral ones, lateral teeth triangular-subulate, 1.4–1.8 mm; upper lip shorter than the lower one, 2.5–3.2 × 1.8–2 mm. Floral buds with wings covered by the standard. Corolla yellow; standard truncate, 10–12 × 7.8–8.2 mm, sericeous on the back; wings 9–10.5 mm, with a tuft of hairs on basal gibbosity; keel 9.5–10.5 mm, sericeous on outer faces. Staminal tube 6.5 mm long, anthers yellow, rounded at apex, upper ones elliptical, 1.5–1.6 mm, lower ones ovate-lanceolate, 0.8 mm. Pistil 12 mm; stigma papillose, oblique. Pod sericeous, oblong, apiculate, flattened, pale-brown, 12–14 mm long, 2–4 seeded. Seeds ovate, flattened, blackish-brown, 1.8–2.2 × 1.6–1.7 mm.

Phenology:— Flowering May to June, fruiting June to July.

Karyology:— The somatic chromosome number of Genista nuragica was found 2 n = 2x = 18+0-2 B on material from Montarbu di Seui (Cusma Velari & Feoli Chiapella, new count, Fig. 3).

Seed micro-morphology:— Cell boundaries are indistinguishable. Seed coat is homogeneous and appears irregularly loosely rugose-reticulate, with smoothed, short and large papillose wrinkles ( Fig. 4 E–F ).

Distribution and Habitat:— Genista nuragica exclusively occurs only in the Barbaricino biogeographic sector ( Fenu et al. 2014), on the mountain stands of Montarbu di Seui (CE Sardinia), on rocky formations locally known as ”Tacchi d’Ogliastra” ( Fig. 1 ). The species grows on Mesozoic limestones at an elevation of 1250–1310 m a.s.l., on windy ridges characterized by lithosoils and bioclimatic conditions Mediterranean pluviseasonal oceanic with a lower supramediterranean thermotype and lower humid ombrotype according to the Rivas-Martínez classification ( Bacchetta et al. 2009). Usually, it is a member of orophilous dwarf shrub plant communities characterized by the occurrence of some endemic taxa, such as Anthyllis hermanniae L. (1753: 720) subsp. ichnusae Brullo & Giusso (2006: 311) , Helianthemum morisianum Bertoloni (1844: 374) and Sesleria barbaricina ( Arrigoni 1983: 270) Arrigoni (2006: 43) .

Etymology:—The specific epithet refers to the Nuragic civilization of Sardinia (Bronze Age).

Notes:— Within the species belonging to Genista salzmannii group, G. nuragica seems to be the most closely related to G. desoleana , but several morphological features allow to distinguish these taxa. In particular, the populations of G. desoleana from the type locality (Badde Urbara, Cuglieri, OR) are well differentiated from G. nuragica for the bigger size (30–60 cm tall), stems not very rigid, bracteoles linear-lanceolate, 2–3 mm long, longer than the pedicel, calyx 5.5–6 mm long with hairs 0.3–0.8 mm long, lower lip 3.5–4 mm long, teeth triangular, the central one 1.4–1.6 mm long, the lateral ones 0.9–1.4 mm long, upper lip 1.6–1.8 mm wide at the base, standard retuse at apex, 9.5–10.5 × 9–9.2 mm, keel 9–9.5 mm long, anthers apiculate at apex, the upper ones 1.6–1.8 mm long, the lower ones 1–1.1 mm long, pod 18–22 mm long, 5–7 seeded, seed brown-olivaceous, 2.8–3.0 × 2–2.3 mm.

Furthermore, the two species have different ecological requirements, since G. nuragica is a calcicolous plant exclusively found on windy ridges, while G. desoleana is linked to siliceous volcanic substrates and grows on plateaux with developed soils at lower elevation never exceeding 1,000 m a.s.l. From the bioclimatic point of view, the latter species is localized within the upper meso-Mediterranean belt ( Bacchetta et al. 2009).

Additional specimens examined (paratypes):— ITALY. Sardinia: Montarbu di Seui (Seui, OG), 30 May 2017, G. Bacchetta, A. Cuena, M. Fois, M. Porceddu s.n. (CAG!).

Figures

FIGURE 1. Distribution map of Genista sect. Erinacoides in Sardinia and Corsica.

FIGURE 2. Diagnostic features of Genista nuragica. A. Flowers. B. Open calyces. C. Standard (ventral view). D. Standard (dorsal view). E. Wings. F. Keel (ventral view). G. Keel (dorsal view). H. Staminal tube (open). I. Anthers. J. Pistil. K. Stigma. L. Pods. M. Seeds. N. Bracteoles. Illustration by S. Brullo based on living material coming from the type locality (CAT).

FIGURE 4. SEM micrographs of seed testa of Genista desoleana subsp. martelli (A–B), G. desoleana subsp. desoleana (C–D), G. nuragica (E–F), and G. pichisermolliana (G–H).