Plantago nebularis Hassemer, 2018

Plantago nebularis Hassemer View in CoL , sp. nov. ( Figs. 3–5 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Type: — CHILE. ANTOFAGASTA: Antofagasta: auf dem Cerro Moreno , 8 January 1969, O. Zöllner 3302 (holotype C! [ Fig. 3 View FIGURE 3 ]) .

Diagnosis: —Similar to Plantago johnstonii Pilg. , P. sericea Ruiz & Pav. and P. zoellneriana Hassemer , differing from the first by the linear, sulcate leaves with entire margins and appressed trichomes, and smaller corolla lobes; from the second by the slightly zygomorphic corolla; and from the third by the longer (2.9–3.0 mm) and less pilose bracts, and the larger (3.2–3.5 × 2.0– 2.3 mm) and much less pilose anterior sepals.

Description: —Single rosette herbs, to 35 cm tall, perennial. Taproot moderately thickened, to 5 mm wide; secondary cord-like roots absent. Caudex conspicuous, up to 25 mm long (possibly longer), branching often. Leaves linear, 30–210 × 0.3–0.8(–1.2) mm, sulcate; margins entire; base of leaf wider (1.4–2.0 mm wide) than the linear blade, partially embracing the stem; densely covered with trichomes 0.3–1.4 mm long, silvery, appressed, filiform, terete, with inconspicuous cellular articulations, very slender throughout their entire length and not perceptibly gradually tapering towards the apex (type ’k’). Inflorescence 5–34 cm long. Scape 4.6–33.2 cm long, cylindrical, without conspicuous longitudinal grooves, densely covered with trichomes; trichomes 0.3–1.6 mm long, as on leaves. Spike 0.4–1.8 cm long, with 2–12 flowers. Bracts triangular, 2.9–3.0 × 2.0– 2.2 mm; both faces ranging from glabrous to pilose, margin glabrous to ciliate; keel dark brown, darker and thicker than the light brown membranaceous margins. Flowers hermaphrodite. Anterior sepals elliptic, 3.2–3.5 × 2.0– 2.3 mm; apex broadly obtuse; margins and both faces glabrous except for the keel; keel sparsely pilose on the dorsal face, brown, darker and thicker than the beige hyaline membranaceous margins. Posterior sepals broadly obovate, 3.1–3.4 × 2.9–3.2 mm; apex broadly obtuse; both faces and margins glabrous; keel brown, darker and thicker than the beige hyaline membranaceous margins. Corolla slightly zygomorphic, glabrous; lobes 2.4 × 1.0 mm, elliptic, beige, rather hyaline, apex obtuse. Stamens 4; anthers unknown. Ovary with 2 ovules. Pyxidia broadly pyriform, beige, glabrous, 4.2–4.7 × 3.3–3.6 mm, 2-seeded. Mature seeds unknown; three nearly mature seeds 2.7–3.0 × 1.1–1.7 mm, elliptic to narrowly elliptic; surface reticulate-foveolate, dark brown, smoother on the ventral side; margins hyaline; ventral side concave, dorsal side convex.

Illustrations: — Fig. 4 View FIGURE 4 ; Fig. 16 in Rahn (1983).

Photographs: — Figs. 3 View FIGURE 3 and 5 View FIGURE 5 .

Etymology: —The epithet refers to the environment where the new species occurs, i.e. the summits of Cerro Moreno which are almost perpetually covered in fog (camanchaca) ( Fig. 6 View FIGURE 6 ).

Phenology: —Largely unknown, based only on the two known herbarium specimens of this species. One of them, collected in January (O. Zöllner 3302 [ Fig. 3 View FIGURE 3 ], the holotype), has flowers, one fruit and three nearly mature seeds, while the other specimen (O. Zöllner 7125 [ Fig. 5 View FIGURE 5 ]), collected in July, has only old inflorescences without any flowers, fruits or seeds.

Distribution and habitat: —This species is endemic to the highest areas (ca. 800 m above sea level, possibly up to 1200 m) of Cerro Moreno, which reaches an elevation of ca. 1290 m on the Mejillones Peninsula, ca. 20 km northwest from the city of Antofagasta, Antofagasta region, northern Chile ( Figs. 6 View FIGURE 6 and 7 View FIGURE 7 ). Despite the whole area being a desert (one of the driest in the world), the almost perpetual fog which blankets the summits of Cerro Moreno creates a unique environment where many plant species thrive. Cerro Moreno is partly covered by loma vegetation on the south-western slope at elevations higher than 300 m asl ( Schulz et al. 2011a).

Conservation status: —Critically endangered (CR–B2[a,b(iii)]). The new species is endemic to one locality, i.e. the summits of Cerro Moreno. The area is included in an environmental protection area, the Parque Nacional Morro Moreno, but is frequently visited by tourists and local hiking groups.

Notes: —The new species belongs to Plantago subgenus Psyllium (Tournefort ex Jussieu 1789: 90) Harms & Reiche (1895: 373) section Gnaphaloides Barnéoud (1844: 19) series Sericeae , and is most similar morphologically to P. johnstonii , P. sericea and P. zoellneriana . The new species will be compared and discussed to these three species in turn below. Rahn (1983: 341) lectotypified the name P. johnstonii and commented on its morphology and distribution, mentioning that it was only known from the type kept at GH, which included three specimens mounted on two sheets. However, he also mentioned that “ 150 km further North O. Zöllner made two collections which may belong to this species or to undescribed related taxa”, citing two specimens kept at C: O. Zöllner 3302 and O. Zöllner 7125. He further added that “Both specimens have bracts and sepals like those of P. johnstoni , but leaves are very narrow, 0.8–1.2 mm wide, sulcate, margins entire and with appressed hairs. The first has ascending scapes and spikes with 2–3 flowers, the corolla lobes similar to those of P. johnstoni but 2.4 mm long and 1.0 mm wide, seeds unripe. The stem is not elongated nor branched, leaves to 42 mm long, scape to 134 mm. The second plant has an elongated branched stem, 27 mm long, with leaves 140 mm long, old scapes to 316 mm, probably erect, and old spikes with 18 flowers, but no corollas or capsules are left”.

Rahn (1983) opted to conservatively maintain the two Zöllner plants, both from Cerro Moreno, under his treatment of P. johnstonii , on the grounds that these specimens have similar bracts and sepals. However, he commented that “The material is unfortunately too scarce to permit taxonomic conclusions. Most probably it all belongs to P.sericea . The three collections [I.M. Johnston 5444, O. Zöllner 3302 and O. Zöllner 7125] are surprisingly different, but still undoubtedly related”. Nevertheless, the comparison of the Zöllner specimens with the type of P. johnstonii ( Fig. 8 View FIGURE 8 ; Figs. 14–15 in Rahn 1983) leaves it clear that, from a morphological point of view, these populations could hardly belong to the same species. Both species are perennial, but P. johnstonii is much more robust, its caudex measuring an impressive 25–220 mm (vs. up to 25 mm in P. nebularis ), and its leaves measuring 140.0–174.0 × 4.5–6.7 mm, in stark contrast with the linear leaves of P. nebularis , 30.0–210.0 × 0.3–0.8(–1.2) mm. The caudex and leaves are often more relevant than the flowers for the taxonomy and classification of Plantago ( Rahn 1974, 1996, Hassemer et al. 2015, Hassemer 2016, Hassemer et al. 2017b), which are normally remarkably invariable among groups of closely-related species in this genus (but not always, see the example of P. sericea and P. zoellneriana ).

In addition to the morphological differences, the distribution and habitat differences between P. johnstonii and P. nebularis reinforce the recognition of these species as separate. The type localities of both species are ca. 140 km apart, and no suitable environment for either species was found between or around these localities during our targeted searches. Furthermore, there are important environmental differences between the type localities of the two species: P. nebularis occurs at the perpetually-foggy summits of Cerro Moreno, at an elevation of 800 m and possibly up to 1200 m; whereas P. johnstonii occurs (or used to occur, see more below) close to a natural spring at the base of a rocky cliff near the coast, at 300–400 m, in an area where fog is not reported. Both species are found in unique habitats which are environmentally suitable “islands” in what is otherwise a desert. Additional attempts to search for these two species are warranted, because despite our targeted searches, other such “islands” of suitable microhabitat nevertheless could be present in the steep coastal mountain topography in this area. Rahn (1983) hypothesised that these unique habitats effectively isolate these Plantago populations and may have played a role in their divergence. Referring to the only known collection of P. johnstonii (I.M. Johnston 5444) and to the two known collections of P. nebularis (O. Zöllner 3302 and O. Zöllner 7125), Rahn (1983) mentioned that “Differentiations in small populations in isolated, marginal habitats can undoubtedly be very rapid, so the presence of the three populations may be explained as the result of relatively recent long-distance dispersal” and that “So the three collections from Northern Chile could also be old relicts in their isolated habitats, from a time when the climate was more humid there”. Analyses of molecular phylogenetic data are warranted to test Rahn’s (1983) evolutionary scenarios. Furthermore, coastal arid northern Chile is recognised as an important area for biodiversity discovery ( Johnston 1929a, 1929b, 1929c, Pinto & Luebert 2009), due to many species having narrow distributions, and also to the very short and sporadic rain episodes, when almost all plants develop and flower.

Plantago nebularis also shares some important morphological similarities with P. zoellneriana ( Figs. 12 View FIGURE 12 –13 in Rahn 1983), mainly the slightly zygomorphic corolla and the very long scapes (both also present in P. johnstonii ), but differs from this species principally by the bracts being longer (2.9–3.0 vs. 2.3–2.5 mm) and less pilose, and the anterior sepals being larger (3.2–3.5 × 2.0–2.3 vs. 2.9–3.1 × 1.3–1.9 mm) and much less pilose. Furthermore, the type locality of P. nebularis is ca. 1270 km distant from the nearest locality of P. zoellneriana , in Curicó, central Chile. Nevertheless, the bracts of P. nebularis are variable in regards to pilosity (ranging from glabrous to pilose), so that we acknowledge that this might not be a reliable character to separate these two species; this is aggravated by the low number of examined specimens of these species, especially of P. nebularis . More collections of these species, especially of P. nebularis , are necessary to clarify this question.

Plantago nebularis also shares morphological similarities with P. sericea subsp. sericea , from which it differs mainly by the much shorter stems, slightly zygomorphic corolla (vs. actinomorphic), and corolla lobes equalling the length of the sepals. Plantago sericea subsp. sericea is not recorded in Chile, but occurs in mountains in Peru, Bolivia and north-western Argentina, at elevations of 2100–4150 m ( Rahn 1981). Despite Knud Rahn’s comprehensive studies, we consider that P. sericea is a particularly poorly-understood species complex distributed in high-elevation areas from Mexico to central Chile and north-western Argentina ( Rahn 1981, 1983), which most likely includes a number of species lumped together under this name.

Despite a targeted search in the field, we were unable to find any plants of P. nebularis during our visits to Cerro Moreno in January 2016. Considering the information on the type specimens (O. Zöllner 3302 [ Fig. 3 View FIGURE 3 ] and O. Zöllner 7125 [ Fig. 5 View FIGURE 5 ]), the species is most probably restricted to the south-western face of Cerro Moreno, which is the only location on the hill with vegetation in an otherwise barren, desert area. This is due to the humidity coming from the sea which condenses and causes the almost perpetual covering of fog on the summits ( Schulz et al. 2011a). Habitats at the type locality appear to be mostly unaltered, and the steepness of the south-western face hinders human settlement. By contrast, the south-eastern face of Cerro Moreno has been developed into a seaside resort (Balneario Juan López), attracting visitors from the nearby city of Antofagasta and other tourists. All things considered, and despite not being able to find the plant, we think it is highly improbable that it has been eradicated, and attribute our failure to the difficulty of exploring the type locality. We argue that further studies are critically necessary for P. nebularis , including its rediscovery at Cerro Moreno, and also ex situ conservation attempts.

It is also worth to mention that one of Peruvian sample at NY (A. Sagastegui N. 11525, collected on 22 May 1984 in Otuzco-Agallapampa , La Libertad, Peru) is morphologically similar to both P. johnstonii and P. nebularis but geographically distant: more than 2,500 km apart from the geographically closest individual of P. nebularis . It is possible that this specimen belong to another, still undescribed species. Further investigations are required to understand the relationships between P. johnstonii , P. nebularis , the aforementioned Peruvian sample and also P. limensis Persoon (1805: 139) ; this last species is part of Plantago series Hispidulae Rahn (1978: 110) (see Rahn 1982).

We would have preferred to designate the holotype among herbarium specimens of this species kept at Chilean herbaria; however, we were unable to find any. All known specimens of the new species were collected by Otto Zöllner Schorr and are kept at the C herbarium.

Additional specimen examined (paratype): — CHILE. ANTOFAGASTA: Antofagasta: en el cerro Moreno a 800 m de altura sobre el mar, 31 July 1973, O. Zöllner 7125 ( C [ Fig. 5 View FIGURE 5 ]) .