Research Article |
Corresponding author: Andrés Moreira-Muñoz ( andres.moreira@pucv.cl ) Academic editor: Yasen Mutafchiev
© 2022 Sergio T. Ibáñez, Mélica Muñoz-Schick, Rosa A. Scherson, Andrés Moreira-Muñoz.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Ibáñez ST, Muñoz-Schick M, Scherson RA, Moreira-Muñoz A (2022) A new species of Diplostephium (Asteraceae, Astereae) from the Atacama Desert, Chile. PhytoKeys 215: 51-63. https://doi.org/10.3897/phytokeys.215.89175
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A new species, Diplostephium paposanum S.T.Ibáñez & Muñoz-Schick, sp. nov., is described for Chile, extending the southern distribution of the genus. Its position within the genus was confirmed by morphological and molecular data, discussed here. The new species was found in a coastal environment, new to the genus, and is geographically far removed from the other Chilean species, which are from the Andes. The formation where it occurs, known as lomas, acts as a biodiversity refuge in hyperarid environments. The presence of D. paposanum in this environment contributes to the evidence of a floristic connection between the Atacama Desert and the Neotropical Andes.
Se describe una nueva especie para Chile, Diplostephium paposanum S.T.Ibáñez & Muñoz-Schick, sp. nov., extendiendo la distribución austral del género. Su posición dentro del género fue confirmada por datos morfológicos y moleculares, discutidos acá. La nueva especie se encontró en un ambiente costero, nuevo para el género, y está geográficamente alejada de las otras especies chilenas, que son de los Andes. La formación donde habita, conocida como lomas, actúa como refugio de la biodiversidad en ambientes hiperáridos. La presencia de D. paposanum en este ambiente contribuye a la evidencia de una conexión florística entre el Desierto de Atacama y los Andes Neotropicales.
Antofagasta, coast, fog oasis, lomas, molecular analysis, Paposo, taxonomy
Análisis molecular, Antofagasta, costa, lomas, oasis de niebla, Paposo, taxonomía
The genus Diplostephium Kunth, in the broad sense, is a diverse group of 111 species (
Diplostephium was defined by Kunth (
The last molecular study of the genus Diplostephium (
Until now, three species of Diplostephium s. s. have been recorded in Chile; D. cinereum Cuatrec., D. tacorense Hieron. and D. meyenii Wedd. (
During a field campaign carried out in December 2020 on the coast of the Atacama Desert, this species was found and collected in Quebrada Botija, an area located in northern Paposo, at an altitude of 170 m (Fig.
Local floras, regional checklists (e.g.
For morphological study, herbarium specimens were dissected and the different morphological components of the plant were studied and recorded for the taxonomic description. Dissected parts were measured under the stereoscopic lens with a scale, and also photographed combining the lens and a camera (Canon G16), and measured afterwards using the software ImageJ (
Because of the complexities of the phylogeny previously explained, and the fact that it was not the goal of this study to generate a genomic study, we decided to perform a Barcoding analysis using two commonly used markers for the Asteraceae, comparing the sequences for the new species to the vast number of sequences for the group available in GenBank.
Genomic DNA were isolated from silica gel-dried leaves using the DNeasy Plant Mini Kit (Qiagen, Valencia, CA, USA) following the manufacturer’s recommendations. Two regions were amplified: The internal external transcribed spacer (ETS) region of nuclear rDNA, using primers 18S-ETS (
For all regions, a polymerase chain reaction (PCR) amplification were performed with 12.5 μL GoTaq Colorless Master Mix (Promega), 2.5 μL of each 10 μM primer, 2.5 μL of 1 mg/ml BSA, 2 μL of DNA template, and distilled nuclease free water for a 25 μL reaction. The PCR reaction followed the protocols of
Products were purified and sequenced using the Applied Biosystems sequencer ABI3500XL at the Pontificia Universidad Católica de Chile sequencing facility, using the primers described previously at a 5 μM concentration. Both forward and reverse strands were sequenced. Electropherograms of the sequenced products were edited and assembled into contigs using the DNA Baser v4 sequence assembly software (Heracle BioSoft SRL, Pitesti, Romania).
Contigs were used to perform an analysis of sequence similarity using the BLASTn (nucleotide) tool implemented in the National Centre for Biotechnology Information website (http://www.ncbi.nlm.nih.gov/). We used the option of highly similar sequences (megablast), which retrieves all sequences available in GenBank that are highly similar (95% or more) to the target sequence.
With the information collected through fieldwork and analysed using the software QGIS (
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.
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:
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.
Illustration of Diplostephium paposanum A distal end of the branch with capitula B details of leaves B1 upper part of the branch covered by leaves B2 adaxial view B3 abaxial view B4 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-Muñoz 3355. Illustration by Andrea Ugarte. Scale bars: 1 cm (A); 5 mm (B1); 1 mm (B2–B4, C–F, H, I); 0.5 mm (G).
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. Ibáñez (A–E), A. Moreira (F).
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 Ibáñez, Pañitrur & Acosta 771. Scale bars: 5 mm (A–C); 2 mm (D–F).
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 (
The species has been observed only in Quebrada Botija (24°30'S, 70°32'W), a locality 55 km north of Paposo (Fig.
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.
Flowers of this species have been observed between November and January. Fruits are dispersed between December and February.
The values obtained using the Red List assessment criteria (
The epithet 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.
After contig assembly and trimming of the primer regions, we obtained 577 basepairs of the ETS sequence, and 824 basepairs of the trnL-F sequence. Both BLAST analyses retrieved highly similar sequences, and both markers obtained species of the genus Diplostephium as the most similar. For ETS, the first 40 sequences retrieved were from this genus, with 95% similarity. For trnL-F, sequences retrieved matched species of the genus Diplostephium with 98.9% similarity. Within the first 40 sequences retrieved, there were only two that did not correspond to this genus, but were still Asteraceae. The new sequences were uploaded to GenBank, with accession numbers OP038910 for D. paposanum trnL-trnF sequence and ON936842 for D. paposanum ETS sequence.
The position of D. paposanum in Diplostephium sensu lato is supported by morphological characters, such as the shrubby and candelabrum-like habit, heterogamous heads with three to four series of phyllaries and alveolate receptacle, disk florets with ecaudate anthers and lanceolate style branches, ribbed and somewhat compressed cypselae with two different sizes of pappus bristles (
Because of the phylogenetic complexity of the genus, we did not infer a phylogenetic position for D. paposanum. Nevertheless, we can assume with a high degree of confidence that genetically this new species is most similar to other species of the genus Diplostephium s.s. A genomic analysis would be very useful to confirm these results.
This species is remarkable because it is the first species of Diplostephium collected at low altitude, with an altitudinal range of between 170 and 700 m, whereas all species previously known were collected between 2500 and 4500 m. The new species is similar to some congeneric species, but has distinctive characters which are similar to other coastal species from the Atacama Desert. For instance, D. paposanum is a rather glabrate plant with leaves which become succulent and terete to clavate with age. These characters are odd in the genus, but are common in sympatric plants, such as in some shrubby Nolana spp. (Solanaceae), Spergularia arbuscula (Gay) I.M. Johnst. (Caryophyllaceae), Heliotropium pycnophyllum Phil. (Heliotropiaceae), or Suaeda foliosa Moq. (Chenopodiaceae). The resinous glands present in D. paposanum are a common character found in other Diplostephium species, which could have led this genus to colonize dry habitats, as has been observed in other xerophytic Asteraceae species.
Despite the fact that it is not common to find high altitude Andean taxa in coastal conditions, some exceptions can be found in the particular conditions of the coastal Atacama Desert, where the coastal fog allows abundant vegetation. This can be seen in Dalea species which, when present in South America, are found mostly in the Andes (
We would like to acknowledge Michael Dillon, a specialist in lomas formations, for his comments and bibliographic material. Also, we acknowledge the contribution of Mauricio Bonifacino for his taxonomic comments, to Vanezza Morales for her contribution in bibliographic material, Carolina Pañitrur and Marcos Acosta for fieldwork support, Diego Soto and Constanza Gatica for help with lab work, and Andrea Ugarte for the precious illustration of the species. This work was done under the FNDR project “Diagnóstico y conservación de la flora costera de la Región de Antofagasta” (funded by GORE Antofagasta, implemented by MMA-SEREMI Antofagasta, and executed by INIA), and the Fondecyt project code 1221879.