Helianthemum raskebdanae, Alonso, Angeles, Crespo, Manuel B., Juan, Ana & Sáez, Llorenç, 2015
|
publication ID |
https://doi.org/ 10.11646/phytotaxa.207.3.3 |
|
persistent identifier |
https://treatment.plazi.org/id/03E11E4E-FFB8-FFF2-FB89-E9F8FC4C3997 |
|
treatment provided by |
Felipe |
|
scientific name |
Helianthemum raskebdanae |
| status |
sp. nov. |
Helianthemum raskebdanae View in CoL M.A.Alonso, M.B.Crespo, Juan & L.Sáez sp. nov. ( Figs. 1−2 View FIGURE 1 View FIGURE 2 )
Planta speciosa sectionis Helianthemum , sed singulari characterum combinatione a ceteris speciebus diversa et facile distinguenda, nempe foliis utrimque glaberrimis, carnosis; racemis paucifloris brevibusque; sepalis subglabris, apice pilis stellatis, radiis longis flexuosis obsito excepto; petalis roseis vel purpureis, magnis; seminibus atrofuscis, minutis papillis translucidis globoso-angulosis dense obsitis. H. maritimum primo intuito aemulans, sed ab eo bene differt imprimis caulibus valde intricatis, foliis glaberrimis, petiolis e pulvinulis incrassatis rubrisque exorientibus, sepalorum pilis apicalibus rigidioribus brevioribusque.
Type:— MOROCCO. Oriental Province: Nador, Ras-el-Ma to Saidia, limestone and sandstone cliffs, 30SWD544883, 24 m a.s.l., 29 April 2013, M.B. Crespo, M.A. Alonso, A. Vicente & J.L. Villar s.n. (holotype ABH 68324!).
Perennial plant, 20−40 cm high, shrubby, intricate. Stems procumbent, basally branched; branches tomentose, covered with both stellate hairs with long soft sinuous branches and fasciculate long setiform hairs. Leaves 5−15 × 1−4.5 mm, ovate-elliptical to widely oblong, with margins revolute to almost flat, glabrous on both sides, shiny, occasionally with some scattered fasciculate hairs on the central nerve beneath; petiole 0.7−1 mm long, glabrous (rarely with some fasciculate trichomes beneath), arising from a reddish (occasionally yellowish) swollen basal pulvinule; stipules 1.3−2.5 × 0.5−0.6 mm, linear to linear-lanceolate, fleshy, present in all leaves attached to the petiolar pulvinule, persistent, green, glabrous, shiny, with only 3−8 setiform hairs on the tip and exceptionally also on margins, about twice as long as the petiole. Inflorescence a 1−4-flowered raceme, 1−3 cm long; bracts linear-elliptic to ovate-oblong, glabrous, with some fasciculate hairs in the basal part and 1−5 setae at the apex; peduncles straight at anthesis, curved downwards at fruiting time, 5−7 mm long, equalling sepal length. Calyx not accrescent in fruit. Outer sepals ca. 2 × 0.5 mm, linear, glabrous. Inner sepals 7−9.5 × 3−4 mm, not accrescent, elliptical, glabrous, shiny, with some scattered stellate hairs in the apical portion with long flexuous branches (up to 0.25 mm long), and minute short fasciculate trichomes on the upper inner part of the overlapped margin, sometimes mixed with simple ones; ribs purplish, prominent. Petals 7.5−15(−17) × 8−11 mm, obovate-flabelliform, pink to purple with yellow-orange base, 1.5−2.5 times longer than the sepals. Capsule 5−6 × 3−4.5 mm, ovoid-ellipsoidal, polyspermous, dehiscing by 3 valves, brown to yellowish-brown, densely covered with minute short fasciculate trichomes. Seeds 1−1.7 × 0.9−1.5 mm, roundish, angulose, blackish, densely papillate, with translucent, globose-angular papillae.
Etymology:—The specific epithet ( raskebdanae ) refers to the native Arabic name of the type locality, Ras-Kebdana, also known as ‘Cabo del Agua’ in Spanish or ‘Cap de l’Eau’ in French.
Habitat:— Helianthemum raskebdanae occurs in crevices of limestone and sandstone maritime cliffs, slightly influenced by the spray of marine water, in the Upper Thermomediterranean Semiarid bioclimatic belt (sensu Rivas-Martínez 2007). It is a component of subhalophilous low scrub growing above the Crithmo-Limonietea Br.-Bl. in Braun-Blanquet et al. (1952: 32), nom. mut., plant communities, together with Calendula stellata Cavanilles (1791: 3) , Daucus gingidium Linnaeus (1753: 242) s.l., Frankenia laevis Linnaeus (1753: 331) , Helianthemum syriacum (Jacq. in Murray 1784: 498) Dumont de Courset (1802: 129), Lagurus ovatus Linnaeus (1753: 81) , Lotus cytisoides Linnaeus (1753: 776) , Micromeria inodora ( Desfontaines 1798: 30) Bentham (1834: 375) , Pallenis maritima ( Linnaeus 1753: 903) Greuter (1997: 47) , and Plantago serraria Linnaeus (1759: 896) .
Distribution:—The new species is found in a narrow area near Ras-el-Ma, in the Oriental Province of Morocco. Only three small subpopulations are currently known ( Fig. 3 View FIGURE 3 ), in an area of about 5 km along the coastline. The first is located in the upper cliffs of Ras-Kebdana, close to the lighthouse and the military facilities, and comprises over 100 mature individuals. The second is about 2.5 km eastward, toward Saidia, in which less than 10 individuals were observed. The third is about 2 km eastwards the latter, near the road to Saidia, and includes over 300 mature individuals well established. Biogeographically, all those sites are located in the Moulouyan-Kabylian Province (sensu Rivas-Martínez 2005), sometimes referred to as the Nekor-Triffa Sector (sensu Sauvage & Vindt 1952) or the Gareb physiographical area (sensu Valdés et al. 2006), to which H. raskebdanae is a narrow endemic. Further work is needed to locate possible additional populations in the neighbouring cliffs of that territory.
Additional specimens examined (paratypes):— MOROCCO. Nador : Ras-el-Ma, Cap de l'Eau, 30SWD547880, 38 m, 29 April 2013, M.B. Crespo, M.A. Alonso, A. Vicente et J.L. Villar s.n. (ABH 68322!, ABH 68324!) ; Morocco. Nador: Ras-el-Ma, Punta del Faro , 30SWD5289, 38 m, 19 April 2009, M.B. Crespo, A. Guilló, L. Sáez, M.A. Alonso, A.Juan et al. s.n. (ABH 59962!) ; Nador : Ras-el-Ma, a unos 2 km de la población, carretera a Saidia, 30SWD559871, 31 m, 11 March 2015, M.A. Alonso, M.B. Crespo et A. Terrones s.n. (ABH 71900!, MA!) .
Taxonomic relationships:—North African taxa of Helianthemum sect. Helianthemum constitute a difficult taxonomic aggregate still poorly known and in need of further work. Most pink-flowered taxa have been included in the H. apenninum Miller (1768 : without page) aggregate (Greuter et al. 1989), and their main characteristics were synthesised and discussed by Raynaud (1985). Several divergent treatments have been proposed for these taxa, with different resulting synonymisation proposals ( Battandier & Trabut 1888, Durand & Schinz 1898, Jahandiez & Maire 1932, Quézel & Santa 1963, Boulos 2000, Soriano 2002). At first sight, H. raskebdanae is close to the Algerian endemic H. maritimum Pomel (1874: 220) ( Table 1). They share fleshy leaves, almost glabrous and shiny inner sepals, and few-flowered racemes with pink flowers. However, other morphological characteristics such as the intricately branched habit, the entirely glabrous leaves, and the presence of reddish pulvinules at the petiole base are exclusive to the former and allow their easy separation ( Figs. 1−2B View FIGURE 1 View FIGURE 2 ). Furthermore, the stellate hairs in the apical portion of the sepals show long, flexuous branches (up to 250 μm) in H. raskebdanae , whereas they are rigid and shorter (ca. 80−100 μm) in H. maritimum ( Fig. 2A View FIGURE 2 ); also, the testa surface is differently ornamented in both species ( Fig. 2C View FIGURE 2 ) and the fasciculate hairs on the fruit valves are longer and stouter in H. maritimum (117−147 × 12.1−14.2 vs. 100−125 × 9.2−10.7 μm) ( Fig. 2D View FIGURE 2 ). Ecologically, H. raskebdanae is a rupicolous plant, growing in crevices of limestone and sandstone cliffs, whereas H. maritimum is found in coastal sand-dune habitats. Connections to other North African pink-flowered representatives of the H. apenninum aggregate are weak. On the one hand, H. virgatum ( Desfontaines 1798: 422) Persoon (1806: 79) , widespread in northwestern Africa (from Libya westwards), differs by its longer erect stems, which bear linear non-fleshy leaves with strongly revolute margins, densely grey-tomentose on both sides; its sepals are wider, densely stellate-tomentose and accrescent in fruit, and the inflorescences are usually longer and many-flowered ( Table 1). This plant has sometimes been treated as a synonym of H. apenninum (i.e. Soriano 2002), or as its variety ( Raynaud 1999), albeit morphological divergence warrants specific separation. The closely related H. ciliatum ( Desfontaines 1798: 421) Persoon (1806: 76) occurs in the southeastern Mediterranean basin, from Tunisia eastwards, and resembles H. virgatum to which sometimes it has been subordinated at various ranks ( Battandier & Trabut 1888, Pottier-Alapetite 1979). They both share the general habit, though H. ciliatum has larger calyces (up to 10 mm long in fruit), subglabrous on the surface and long-ciliate on the ribs, and capsules usually glabrescent. Both H. pergamaceum Pomel (1875: 350) and H. vesicarium Boissier (1849: 50) show also grey-tomentose leaves with stellate hairs on both sides and many-flowered inflorescences, though the calyces are larger, strongly accrescent and swollen in fruiting time, usually with long setose ribs. The former is widespread throughout northwestern Africa (eastwards to Libya) and has papery sepals with a glabrous surface, whereas the latter occurs in the eastern Mediterranean basin (westwards to Tunisia) and has sepals with a stellate-tomentose surface. All those taxa are sufficiently different to be recognised as independent species, as accepted in recent floras ( Jafri & El-Gadi 1977, Greuter et al. 1989, Raynaud 1999, Le Floc’h et al. 2010). Finally, relationships with H. sauvagei Raynaud (1981: 475) are remote. It is confined to the western areas of the High Atlas ( Agadir region), between 300 and 800 m of elevation, and shows tall erect stems up to 60 cm high, green wide and flat leaves ciliate on margins which bear stipules 1.5−2 times longer than the petiole, and flower pedicels glabrous, among other characters. Some other taxa from neighbouring northern territories show some resemblances and are worth of mention ( Table 1), though probably they are not phylogenetically close to the new species. On the one hand, the Balearic endemic H. scopulicola Sáez et al. (1999: 414) also grows in maritime cliffs and shares with H. raskebdanae the glabrous non-accrescent calyces and pinkish flowers. However, in the former the leaves are not fleshy and are white-stellate-tomentose beneath. The pink-flowered H. dianicum Pérez Dacosta et al. (2012: 44) from the southeastern part of the Iberian Peninsula, and its relative H. apenninum widely spread in southern and western Europe, differ by their stems diffuse, not intricately branched, grey-tomentose non-fleshy leaves, and densely stellate pubescent inflorescences and calyces, the latter accrescent in fruit, among other characters. Regarding H. almeriense Pau (1925: 11−12) , at first sight it reminds H. raskebdanae because the shrubby, intricateramose habit, fleshy leaves, and few-flowered racemes. Helianthemum almeriense was described from southeastern Spain (Almería Province), and has also been cited from northeastern Morocco ( Soriano 2002). However, it clearly differs by its entirely glabrous stems (sometimes only with appressed stellate hairs), shorter leaves (up to 10 mm long), the lowermost suborbicular, minute, always lacking basal pulvinules, and flowers typically with glabrous, red-tinged calyces and white-coloured petals (although pink-flowered plants have exceptionally been reported). Relationships with other Spanish taxa, i.e. H. violaceum ( Cavanilles 1793: 38) Persoon (1806: 78) which is closer to H. virgatum , are remote ( López González 1993).
Conservation status:— Helianthemum raskebdanae is a narrow endemic only known from three coastal sites in northeastern Morocco. This is an increasingly popular tourist area, in which urban sprawl is taking place, a fact that can seriously compromise the future conservation of the new species. Fortunately, the subpopulation in Ras-Kebdana occurs in a military area, a fact that is expected to ensure its long-term conservation. Conversely, the second eastern subpopulation is severely threatened by human activities, since it is found close to buildings and is easily accessible from the main road to Saidia. The third easternmost subpopulation includes the highest number of know mature individuals, which grow in a well conserved habitat. The distribution of the new species is very restricted, with an extremely low extent of occurrence (0.53 km 2). A decline in the population is inferred by the quality of the habitat. We therefore recommend that H. rasbkebdanae is categorised as Endangered ( IUCN 2012) based on the criteria B1ab(iii)+2ab(iii). Conservation measures should be implemented to monitor the evolution of those subpopulations and ensure conservation of this interesting new endemic. A first step in that direction should be the addition of H. raskebdanae to the list of endemic taxa of Morocco ( Rankou et al. 2013).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.