Helianthemum origanifolium subsp. africanum M. B. Crespo, M. A. Alonso, A. Vicente & J. L. Villar 2016, subsp. nov.
Creators: name: Crespo, Manuel B.
name: Alonso, Ángeles
name: Vicente, Alicia
name: Villar, José Luis
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Malvales
Cistaceae
Helianthemum
Helianthemum origanifolium
Helianthemum origanifolium subsp. africanum m.b.crespo, m.a.alonso, a.vicente &amp; j.l.villar

description: Helianthemum origanifolium subsp. africanum M.B.Crespo, M.A.Alonso, A.Vicente & J.L.Villar subsp. nov. (Figs. 1 − 3)
Planta notabilis sectionis Pseudocisti, sed singulari characterum combinatione ad ceteris subspeciebus H. origanifolii diversa et facile distinguenda praecipue pilis stellatis tota destituta et indumento caulium homotricho, longis pilis setiformibus simplicibus bifurcatisque obsita. A subsp. andalusico primo intuito aemulans, sed ab ea bene differt foliis exstipulatis generaliter minoribus rigidioribusque, trichomatibus fasciculatis semper destitutis; racemis paucifloribus, 3−7-floribus; calycibus minoribus usque ad 4 mm longis, in fructu non vel minime accrescentibus (usque ad 5 mm long). Habitat in fruticetibus siccis, solo lapidoso calcareo vel schistoso, ad aridas et calidas terras littorales ditionis Maroccani et Algeriense, ex Africa boreali.
Type:— MOROCCO. Oriental Province: Nador, Bni Chiker,pr.AïtAmar, road to Charrana, 35º22’13”N, 2º59’45”W [UTM:30SWE003141], 345 m a.s.l., loamy soils, 13 March 2015, M.A. Alonso, M.B. Crespo & A. Terrones s.n. (holotype ABH-71922!; isotype MA!).
Perennial plant, suffruticose (Fig. 1); caudicle 1 − 3 cm, thickened. Stems 13 − 40 cm, diffuse, prostrate-ascending, reddish or yellowish, ± densely hairy, with whitish hairs 0.8 − 1.3 mm, simple and bifurcate (rarely apparently fasciculate after fusion of two or more bifurcate ones) (Fig. 2a). Leaves (5 −)8 − 18 × 3 − 8(− 13) mm, ovate to ovate-lanceolate, obtuse to subacute, with flattened margins, rounded or slightly cuneate at the base, subglabrous on both sides, with bifurcate, setose hairs 0.9 − 1.3 mm long, mostly disposed on margins and on the midrib (occasionally also scattered on both sides) (Fig. 1c, 3a. 1, 3a. 2); petiole 1 − 2 mm, densely covered with bifurcate, setose hairs, stipules lacking. Inflorescence of racemose cymes, simple or sometimes with a short branch at the base; axis densely tomentose, usually whitish, coated with stellate hairs showing flexuous branches, usually mixed with reddish, short glandular hairs and sometimes with a few simple hairs, bifurcate, ca. 1 mm long. Flowers 3 − 7, densely disposed (Fig. 1b); pedicels 5 − 8 mm and ± straight, up to 10 mm and strongly curved at the base in fruiting time; bracts 1 − 2 × 0.3 − 0.4 mm, triangularlanceolate to linear, glabrous or ciliate only on margins. Outer sepals 1 − 2 mm, linear. Inner sepals 2.5 − 4 × 1.5 − 2.5 mm, not or very scarcely accrescent in fruit (up to 5 mm long), ovate to oblong-elliptic, subacute to obtuse; ribs greenish or yellowish, prominent, bearing simple and bifurcate hairs ± densely disposed, setose, up to 1 mm long, as well as with adpressed stellate hairs with flexuous branches; intercostal spaces coated with stellate hairs with flexuous branches. Petals 4 − 8 mm, obovate, longer than sepals, yellow. Capsule 3 − 4.5 × 2 − 2.8 mm, shorter than calyx, ovoid, covered with short hairs, fasciculate, with erect branches, mostly concentrated on the apical part, glabrous in the lower half. Seeds ca. 1 × 1 mm, subpyramidal, smooth, light brown to yellowish-brown, dark-coloured at the hilum.
Etymology:—The subspecific epithet (africanum: African, from Africa) refers to the continent to which it is native, since it is so far the only representative of the H. origanifolium complex occurring in northern Africa.
Habitat:— Helianthemum origanifolium subsp. africanum grows in open grasslands and dwarf shrub plant communities, mostly on calcareous or schistose soils, and occasionally on rock crevices and maritime cliffs not strongly influenced by marine salt spray. It mostly occurs in hot and dry territories, from the sea level up to 1000–1200 m elevation, in both the Thermomediterranean semiarid-dry and the Mesomediterranean dry-subhumid bioclimatic belts (Rivas-Martínez 2007).
Distribution:—The new North African subspecies is only known from the littoral plains and low mountains comprised from the surroundings of Al-Hoceima (Taza-Al Hoceima-Taounat Province) and the Melilla Peninsula (including the Spanish Autonomous City of Melilla) in the Oriental Province of north-eastern Morocco, to the Oran Province in north-western Algeria (Fig. 5). Biogeographically, this area belongs to the Moulouyan-Kabylian Province (Rivas-Martínez 2005), to which the newly described subspecies should be regarded as endemic.
Other specimens seen (paratypes):— ALGERIA. Oranie Region: Oran, montagnes, [35º42’N, 0º34’W], March 1839, Bové s.n. (P-06687796!, B!); Oran, coteaux secs, 12 April 1842, M. Durieu s.n. (P-06687799!, P-06687805!, P-06687807!); Oran, 1842, Delestre s.n. (P-06687797!, P-06687814!); Oran, May 1842, M. Durieu s.n. (P-06687798!); Oran, in collibus, 1850, M. Munby s.n. (P-06687794!); Oran, in collibus siccis, 1851, M. Munby s.n. (P-06687809!); Oran, sur les coteaux incultes, 12 March 1852, B. Balansa s.n. (P-06687793!, P-06687803!, P-06687811!, B!); Oran, 1852, Gouget s.n. (P-06687792!); Oran, 11 April 1856, E. Cosson s.n. (P-06656014!, P-06687813!); Oran, 23 April 1883, A. Debeaux s.n. (P-04638615!); Oran, 8 March 1891, F. Doumergue s.n. 40 (P-04729014!, MA-81453! as var. oranense Pau in sched.); Oran, March 1912, L. Rotereau s.n. (P-06656023!); Oran, taillis et brousailles, 15 December 1940, A. Faure s.n. (P-04750481!); Oran, falaises à la Batterie Espagnole, [35º44’N, 0°42’W], 8 May 1852, E. Cosson s.n. (P-06687808!, COI-00061875 [photo!] as var. major Willk. in sched.); Oran, Batterie Espagnole, March 1912, Ch. d’Alleizette s.n. (P-06656015!); ibidem, April 1922, Ch. d’Alleizette s.n. (MA-81452!); Oran, Djebel Santo, pr. Mers el Kebir, [35º43’N, 0º42’W], 26 January 1851, G.-L. Durando s.n. (P-06687800!, P-06687806!); Djebel Santo, près d’Oran, 16 March 1852, G.-L. Durando s.n. (P-06656018!, P-06687801!); Oran, Djebel Murdjajo, [35º40’N, 0°48’W], 500 m, 29 July 1952, B. de Retz 32360 (P-04637873!); Oran, rochers des falaises, [35º42’N, 0°38’W], 8 April 1856, E. Bourgeau s.n. (P-06656020!, P-06687795!, P-06687802!, COI-00061876 [photo!]); Oran, falaises de Canastel, [35°45’15”N, 0°33’47”W], 2 April 1932, R. le Cesve s.n. (P-04637874!, P-04729015!, P-04747854!, P-06656017!, MA-424890!); Oran, coteaux de Santa-Cruz, [35º42’33”N, 0º39’55”W], December 1886, F. Garrigues s.n. (P-06656022!); Oran, à Santa Cruz, bords du Chemin des Planteurs, 29 May 1904, A. Faure s.n. (B!); ibidem, 12 March 1905, A. Faure s.n. (P-06656019!, B!); Oran, Santa Cruz, broussailles, March 1921, H. d’Alleizette s.n. (MA-81451!); Oran, à Santa-Cruz, pelouses et broussailles, 20 March 1930, A. Faure s.n. (MA-81454, MA-81454- 2!); Oran, maquis des pentes de la Santa Cruz, 17 February 1931, A. Dubuis s.n. (P-04637976!); Oran, 19 April 1850, G.-L. Durando s.n. (P-06687812!); Aïn-Témouchent, maquis du litoral à Camerata, [35 20’N, 1°19’W], 4 June 1936, L. Faurel s.n. (P-04637977!); Tlemcen, Nemours [Djemaa el Ghazaouet], [35°05’N, 1º51’W], 1869, Warnier s.n. (P-06687815!); Mostaganem, Ouillis [Ben Abdelmalek Ramdane], Dahra, [35°56’N, 0°05’W], 13 May 1875, E. Cosson s.n. (P-06687810!); MOROCCO. Taza-Al Hoceima-Taounat Region: Alhucemas [Al-Husayma], Yebel Malmusi, in declivibus calcareis (Littore rhiphaeo), 100 m, 3 May 1927, P. Font Quer s.n. (as H. origanifolium f. leiocladum Pau & Font Quer; BC07045!, MPU006285!, MPU006286 [photo!], MA-81449!, MA-81449-2!); Zaxdir [Ajdir], March 1931, Mas Guindal s.n. (MA-321823!); Oriental Region: Nador, Bni Chiker, península de Melilla, pr. Cabo Tres Forques, 35º22’46”N, 2º58’52”W [UTM: 30SWE016151], 360 m, 18 April 2009, M.B. Crespo et al. s.n. (ABH-68479!); ibidem, carretera hacia Cabo Tres Forques, 35º22’30”N, 2º58’56”W [UTM: 30SWE016146], 340 m, 11 March 2015, M.A. Alonso, M.B. Crespo & A. Terrones s.n. (ABH-71914!); Beni-Sicar [Bni Chiker]; Península de Melilla, Mazuza [Farhana], 27 December 1932, Pardo y Martí 208 (MA-321859!). SPAIN. Ciudad Autónoma de Melilla: Melilla, primavera 1912, Xiberta 742 (MA-81450!); Melilla, Bco. del Nano, 1 June 1915, A. Caballero s.n. (MA-81080!); Melilla, à Hidum, coteaux calcaires-siliceux, 28 December 1930, Mauricio (as H. dichotomum var. mairei Sennen, MPU-008386 [photo!]); ibidem, coteaux sablonneux, 29 April 1934, Sennen & Mauricio s.n. (MA-159182!, MA-159751!).
Taxonomic relationships:—Indumentum features are highly diagnostic for differentiation among taxa in the Helianthemum origanifolium aggregate. In particular, H. origanifolium subsp. africanum lacks stellate trichomes on stems and leaves, a feature allowing an easy and secure separation from the remaining Iberian and Balearic subspecies.
The general aspect of the North African plants resembles H. origanifolium subsp. origanifolium (endemic to south-western Iberian Peninsula) and H. origanifolium subsp. saetabense (endemic to south-eastern Iberian Peninsula) (Fig. 5), though sepals in both latter are constantly larger (3.5 − 6 mm long) and accrescent in fruit (up to 6.5 − 8 mm long). Furthermore, important differences in leaf and stem indumentum are found: leaves in H. origanifolium subsp. origanifolium are hairy and only bear characteristic shorter (ca. 1 mm), adpressed, fasciculate, setose trichomes arranged in groups of 4 (sometimes of 2, 3 or 5) on the midrib and margins (Fig. 3b. 1–b. 2), lacking stellate hairs with flexuous branches; stems are densely covered with soft stellate hairs of adpressed, slender, flexuous branches up to 0.2 mm long, accompanied by some scattered setose, patent hairs in groups of 2 − 4(− 5), up to 0.9 mm long, similar to those on leaves (Fig. 2b). Leaves in H. origanifolium subsp. saetabense show also shorter (0.4 − 0.6 mm long), mostly simple and bifurcate hairs (Fig. 4c. 1–c. 2), and sometimes stellate trichomes scattered beneath, with short flexuous branches (0.2 − 0.4 mm); the stems bear stellate trichomes (0.3 − 0.4 mm long) and some occasional simple and bifurcate hairs (0.4 − 0.8 mm long), like those on leaves (Fig. 2d).
At anthesis, petals (4 − 8 mm long) and sepals (2.5 − 4 mm long) are similar in size to those of both H. origanifolium subsp. glabratum (Willkomm 1862: 147) Guinea & Heywood in Guinea (1954: 133) (endemic to eastern Iberian Peninsula) and H. origanifolium subsp. serrae (Cambessèdes 1827: 216) Guinea & Heywood in Guinea (1954: 134) (endemic to the Balearic Islands) (Fig. 5), the sepals being constantly smaller than in the other subspecies of the aggregate. Both subspecies above also show sepals markedly accrescent in fruit, and leaves coriaceous, mostly subfleshy and nearly glabrous, sometimes only hairy on margins and midrib. However, unlike in both latter taxa, leaves in H. origanifolium subsp. africanum are larger and look herbaceous (neither markedly fleshy nor coriaceous). The indumentum is formed with bifurcate, setose trichomes, lacking stellate or fasciculate adpressed hairs like those characterising both cited congeners (Fig. 2e–f, 4a. 1–a. 2, 4b. 1–b. 2)
Large individuals of Helianthemum origanifolium subsp. africanum are sometimes found in rainy mountain areas of Algeria, and they show some general resemblance to representatives of both H. molle (endemic to northeastern Iberian Peninsula) and H. origanifolium subsp. andalusicum (Font Quer & Rothmaler 1934: 163) Rivas Martínez (2002: 702) (endemic to southern Iberian Peninsula) (Fig. 5), due to the usually large and soft herbaceous leaves. However, both latter taxa have stellate hairs of different sizes with flexuous branches on stems, a character that allows an easy segregation from the North African taxon. Furthermore, H. origanifolium subsp. africanum lacks stipules in the uppermost leaves and the stem indumentum is formed with long (up to 1.3 mm), setose, simple or bifurcate hairs; these setose trichomes are absent in H. molle, and they are mostly fasciculate and shorter (up to 1 mm) than in H. origanifolium subsp. andalusicum (Fig. 2c, 3c. 1–c. 2). Furthermore, H. molle is usually more densely villous and larger in all its parts, namely inflorescences bear usually 5 − 12 flowers, sepals are 4 − 7 mm long at anthesis (accrescent in fruit up to 7.5 − 10 mm long), petals 6 − 12 mm, and capsules 4 − 6 mm long (measurements taken from materials in Appendix 1, and according to López González 1993).
Relationships to other Iberian endemic taxa in some extent related to the H. origanifolium aggregate, such as H. conquense or H. hieronymi Sennen (1929: n. 6717), are very weak and are mostly based on the shared leaf glabrescence. In fact, both taxa differ considerably by many important characters. Helianthemum conquense is a subshrub endemic to Huete-Buendía area (Cuenca province) with some disjunct populations in the Ebro Valley (which however are in need of further research). It shows erect, tomentose branches, bearing leaves lanceolate-spatulate, cuneate at the base, subfleshy, and almost sessile; H. hieronymi is endemic to Sierra de Espuña, los Donceles and la Pila (Murcia and Albacete provinces) and is also an ascending or erect subshrub, with subglabrous branches bearing leaves cuneate at the base and long ciliate on margins and midrib, the uppermost with deciduous stipules, and inflorescences manyflowered, paniculate-ramose, subcorymbose (see additional details in López González 1993). Therefore, in our opinion both taxa deserve specific rank and should not be confused with neither H. origanifolium subsp. africanum nor other members of the aggregate.
Note on species concepts in Helianthemum:—According to the morphological traits of the taxa belonging to the aggregate of Helianthemum origanifolium, the taxonomic treatment adopted here is widely in agreement with Mateo et al. (2013). Furthermore, segregation of H. origanifolium and H. marifolium at species rank is favoured as usually assumed in most western Mediterranean floras (Bolòs & Vigo 1990, Greuter et al. 1984, Mateo et al. 2013, Proctor & Heywood 1968, Quézel & Santa 1963, Raynaud 1999), based mainly on the different density, distribution and nature of leaf indumentum. This solution avoids acceptance of sympatric occurrence of several subspecies in a single site, which should be contrary to the widely assumed definition of subspecies rank, based on geographical or ecological isolation diminishing genetic flow (Avise & Ball 1990, O’Brien & Mayr 1991, Hamilton & Reichard 1992, Crespo et al. 1998, Ellison et al. 2014). However, sympatry of subspecies can be accepted in those cases in which phenological asynchrony or ploidy level minimise genetic exchange (Arista et al. 1997, Morales 2010); but this is not the case of the concerned pair of species, which can grow together and have a partially overlapping flowering time.
Helianthemum origanifolium subsp. africanum is very homogeneous in the indumentum and floral characteristics. It shows, however, some morphological variation in leaf size, shape and texture, probably related to local environmental conditions, which parallels other subspecies of the aggregate in southern and eastern Iberian Peninsula (Guinea 1954, López González 1992, 1993). Actually, plants from drier sites display smaller and more coriaceous leaves, while plants from more humid mountain areas are usually larger, with larger leaves and sometimes larger petals. Conversely, indumentum characteristics are constant and allow to differentiate all the taxa of this taxonomic complex. Some individuals are also found, showing narrower leaves with somewhat attenuate basis. No clear ecological or biogeographical patterns seem to justify such morphological changes, and therefore they do not deserve taxonomical recognition. This variation is likely responsible for H. molle being cited in Algeria as H. origanifolium var. majus Willkomm (1862: 147) or as H. origanifolium s ubsp. molle (Quézel & Santa 1963; Letreuch-Belarouci et al. 2009; Medjahdi et al. 2009). However, as discussed above, the latter taxon is endemic to the eastern Iberian Peninsula (López González 1993, Proctor & Heywood 1968) and exhibits remarkable differences in flower, fruit and indumentum features which warrant a safe circumscription.
The newly described North African subspecies does not differ from H. origanifolium f. leiocladum Pau & Font Quer in Font Quer (1928: num. 418), a taxon described from Djebel Malmusi (Bocoya, between Al-Husayma and Ajdir, northeastern Morocco) which was separated from the typical Iberian plants on the basis of the different nature of the stem indumentum (“ A planta algarbiense (Lusitania) caulibus majis glabrescentibus differt ”). Similarly, plants named H. dichotomum var. mairei Sennen (1936: 123), which were harvested in Hidum (close to Melilla) and were differentiated by its reddish stems, subglabrous leaves and silver-tomentose calyces, also belong to the new subspecies here described. Furthermore, Algerian materials of the new subspecies collected in Oran were labelled H. origanifolium var. oranense Pau (in sched., MA-81453), a name that was never validly published. All those three names fit our concept of H. origanifolium subsp. africanum, and hence they are included here in synonymy.
description: Published as part of Crespo, Manuel B., Alonso, Ángeles, Vicente, Alicia & Villar, José Luis, 2016, A new North African subspecies in the Helianthemum origanifolium aggregate (H. subg. Plectolobum, Cistaceae), pp. 263-272 in Phytotaxa 252 (4) on pages 265-270, DOI: 10.11646/phytotaxa.252.4.2, http://zenodo.org/record/13676293