Diplostephium paposanum S.T. Ibanez & Munoz-Schick, 2022

Ibanez, Sergio T., Munoz-Schick, Melica, Scherson, Rosa A. & Moreira-Munoz, Andres, 2022, A new species of Diplostephium (Asteraceae, Astereae) from the Atacama Desert, Chile, PhytoKeys 215, pp. 51-63 : 51

Diplostephium paposanum S.T. Ibanez & Munoz-Schick sp. nov.

Figs 2 , 3 , 4

Diagnosis.

D. paposanum is distinctive from most species of the genus because of its lack of tomentose or lanate hairs on its vegetative parts, including the adaxial side of the leaves. Additionally, D. paposanum has glandular succulent leaves, and short branches with leaves that are glabrate or scarcely puberulous in the apical section of long shoots.

Type.

Chile. Región de Antofagasta: Norte de Paposo, Quebrada Botija, 24°30.334'S, 70°32.834'W, alt. 170 m, 14 Oct 2021. A. Moreira-Muñoz 3355 (holotype: SGO). Norte de Paposo , Quebrada Botija, 24°30.334'S, 70°32.834'W, alt. 170 m, 15 Dec 2020. A. Moreira-Muñoz 3204 (paratype: SGO) .

Description.

Shrub up to 70 cm tall, subglobose, resinous, generally glabrate but puberulous with hairs mixed with stipitated glands in younger twigs, with ramified erect, indeterminate, ascending, long branches, and shorter, rarely ramified, ascending lateral branches of up to 10 cm borning mostly near the apex of long branches, base of long branches naked, covered with leaves scars. Leaves alternate or fasciculate, densely covering the upper part of the branches and decreasing downward, (1-)2-5 (-8) × 0.3-0.8 mm, succulent, lamina strongly revolute, hence clavate to terete, sessile, covered with sunken glands, younger leaves in plantlets laminar, linear-oblong, with 1-2 teeth at each side of the lamina. Capitula solitary or rarely in pairs, terminal in short lateral branches, heterogamous, radiate. Peduncles (1.5-)2.8-3.9 (-5.5) mm long, often with peduncular bracts 1.0-2.3 × 0.3-0.8 mm, similar to leaves but subulate and base swollen. Involucre 4.1-6.1 × 3.0-4.5 mm, cylindrical; phyllaries arranged in 3-4 series, acute to obtuse, margin hyaline, central rib visible on both sides; outer phyllaries 1.3-2.6 × 0.5-0.8 mm, subulate to deltoid; middle phyllaries 2.4-3.8 × 0.6-0.9 mm, subulate to lanceolate, with or without distal purple spot; inner phyllaries 3.7-4.2 × 0.8-1 mm wide, linear-lanceolate with a distal purple spot; receptacle 1.0-1.5 mm diameter, convex, alveolate, epaleate. Ray florets 7-10, pistillate; corolla white, tube 2.3-4.2 × 0.3-0.4 mm, limb 4.2-7.1 mm × 1.6-2.2 mm, elliptic, minutely 3-lobed; style glabrous, 2.8-4.4 × 0.1-0.2 mm, linear, style branches 0.8-1.7 × 0.1-0.2 mm, linear, flat, with a purple marked line on the middle. Pappus composed of 17-36 bristles of two lengths, short bristles 1.2-2.1 mm, long bristles 3-7.3 mm, scabrid becoming barbellate towards apex. Cypselae of ray florets 1.4-2.9 × 0.4-0.8 mm, shape as in disk florets; carpopodium 1.4-1.9 × 0.4-0.8 mm. Disk florets 10-20, bisexual; corolla yellow, tube 4.3-6.0 × (0.5-)1.0-1.2 mm, narrowly infundibuliform, linear at the base, limb of 5 lobules, each 0.6-1.1 × 0.3-0.6 mm, deltoid; anthers 2.4-3.5 × 0.2-0.3 mm, ecaudate, cuneate, apical appendage deltoid, filaments 1.2-1.8 × 0.05-0.1 mm; style 6.3-7.1 × 0.2 mm, linear, style branches 1.7-2.3 × 0.2 mm, lanceolate, apex acute, distal end straight. Pappus as in disk florets. Cypselae of disk florets 1.7-3.4 × 0.4-0.8 mm, fusiform, slightly compressed, ribbed, villous; carpopodium present, 0.1 × 0.2 mm.

Other material examined.

Chile. Región de Antofagasta. Quebrada Botija , 24°31.072'S, 70°31.835'W, alt. 525 m, 4 Dec 2021. S.T. Ibáñez, C. Pañitrur & M. Acosta 771 (SGO) .

Distribution.

The species has been observed only in Quebrada Botija (24°30'S, 70°32'W), a locality 55 km north of Paposo (Fig. 1 ), on the coast of the Atacama Desert in the Antofagasta Region of Chile.

Habitat.

The only population found was observed in a gorge system, growing from fissures of the ravine walls, or at the bottom of the gorge, often rooting in weathered rocks. The altitudinal range of this species is between alt. 170 and 700 m which suggests that species occurrence is influenced by the presence of the fog from the ocean. It can be found together with species such as Spergularia arbuscula (Gay) I.M. Johnst., Copiapoa boliviana (Pfeiff.) F.Ritter, Proustia pungens subsp. tipia (Phil.) Luebert, Cristaria integerrima Phil., Eremocharis fruticosa Phil., and Jarava tortuosa (E. Desv.) Peñail. Above the gorges, the vegetation is dominated by Copiapoa solaris (F. Ritter) F. Ritter.

Phenology.

Flowers of this species have been observed between November and January. Fruits are dispersed between December and February.

Conservation status.

The values obtained using the Red List assessment criteria ( IUCN 2019) classify this species as "Critically Endangered", based on the criteria B1ab(iii), C2a(ii) and D. After an extensive search of the area, the only population of this species was found in Quebrada Botija, with an extent of occurrence of 4.6 km2 and composed of no more than 20 individuals. Within the area delimited as the extent of occupation, there is a small mining exploitation currently active, in which extracted material is transported using heavy weight trucks moving along the bottom of the gorge in which the species grows. Furthermore, lomas formations are currently threatened by the decreasing amount of humidity reaching the coast in hyper arid Chile, which has led to a notorious declination of vegetation at that latitude ( Schulz et al. 2012). Literature and field observation has confirmed vegetation dieback, especially between Botija and Tocopilla ( Schulz et al. 2011), where high percentages of individuals of species such as Copiapoa solaris are currently dead.

Etymology.

The epithet Diplostephium paposanum means "from Paposo". Paposo is a small village located next to the foothills of the coastal cliffs which is the nearest urban centre to the species described.

Figures

Figure 1. Location of Diplostephium paposanum. The red dot indicates the location of " Quebrada Botija ", the type locality of the new species.

Figure 2. Illustration of Diplostephium paposanum A distal end of the branch with capitula B details of leaves B 1 upper part of the branch covered by leaves B 2 adaxial view B 3 abaxial view B 4 transversal view C capitulum in dispersion of fruits D capitulum in bloom E disk florets with emerging style branches F disk florets with emerged and open style branches G detail of a cypsela of a ray floret H ray floret, including cypsela. Note the differences in length of pappus bristles I detail of a single pappus bristle. All images drawn from Moreira-Munoz 3355. Illustration by Andrea Ugarte. Scale bars: 1 cm (A); 5 mm (B 1); 1 mm (B 2 - B 4, C-F, H, I); 0.5 mm (G).

Figure 3. Diplostephium paposanum in habitat A general view of the type location " Quebrada Botija " B, C habit of individuals, growing on rocky ledges rooting on rock crevices D inflorescences on distal branches E lateral branchlets with terminal inflorescences F capitulum with fully unfolded style branches E, F note the colour differences on yellow disk florets with closed style branches and the mature purple disk florets with unfolded style branches. Photographs by S. Ibanez (A-E), A. Moreira (F).

Figure 4. Detail of reproductive organs A-C capitula A capitulum showing early stages of development, with only anthers of disk florets and style branches of ray florets not unfolded B capitulum showing style branches of disk florets unfolded C capitulum with mature cypselae and their respective pappus fully developed D-F individual florets and fruits D disk florets with style branches barely unfolding E ray florets with developed style branches F mature cypsela of a disk floret. All images from Ibanez, Panitrur & Acosta 771. Scale bars: 5 mm (A-C); 2 mm (D-F).