Dahlia tamaulipana Reyes, Islas & Art. Castro, 2018

Reyes-Santiago, Jerónimo, Islas-Luna, María De Los Ángeles, Macías-Flores, Rafael Guadalupe & Castro-Castro, Arturo, 2018, Dahlia tamaulipana (Asteraceae, Coreopsideae), a new species from the Sierra Madre Oriental biogeographic province in Mexico, Phytotaxa 349 (3), pp. 214-224 : 216-221

publication ID	https://doi.org/ 10.11646/phytotaxa.349.3.2
persistent identifier	https://treatment.plazi.org/id/03C5DE13-FFBE-FFB7-FF42-FCFCE321FA89
treatment provided by	Felipe
scientific name	Dahlia tamaulipana Reyes, Islas & Art. Castro
status	sp. nov.

Treatment

Dahlia tamaulipana Reyes, Islas & Art. Castro View in CoL sp. nov. ( Figures 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Dahlia tamaulipana Reyes, Islas & Art. Castro ; D. tubulatae Sørensen affinis, sed caulibus manifeste sexangularibus et villosis supra nodos et basi petiolorum (vs. cylindricis, glabrescentibus), internodiis 3–5.5 × 1–1.5 cm [vs. 5–9.5 (–12) × 0.3–0.7 cm], stipellis ex primo pari ad tertium par foliolorum praesentibus (vs. solum primo pari foliolorum praesentibus), inflorescentia (1–) 15–25 capitulis [vs. (1–) 2–6 capitulis], capitulis 6.5–10 cm latis, ligulis patentibus (vs. 4.5–6 cm), cypsela clavata pappis coroniformibus (vs. fusiformi sine pappis) differt.

Type:— MEXICO. Tamaulipas: Ciudad Victoria: 11 km al oeste del Parque Ecológico Los Troncones , 1052 m, 23.767585°N, 99.279802°W, 21 November 2012 (fl., fr.), J. Reyes-Santiago & A. Islas-Luna 8172 (holotype MEXU!; isotypes CIIDIR!, IBUG!, IEB!, UAT!, US!) GoogleMaps .

Herbaceous 0.8–2.1 m tall, perennial from rootstock and slightly thickened roots 17–24 cm long. Stems erect, solitary, solid near the base, semi-hollow in the middle, evidently hexagonal, green, villous in the upper portion of the nodes and the base of the petioles, multicellular and whitish hairs, occasionally with holes in its sides, internodes 3–5.5 × 1–1.5 cm, glabrate. Leaves from the middle portion pinnate, sometimes bipinnate, ovate to elliptic in general outline, 25–38 × 15–30 cm; petioles 8–14 × 0.3–0.7 cm near the base, evidently connate-perfoliate, solid; stipels lanceolate to ovate, 3.5–7 × 1.7–3 cm, present from the first to the third pair of leaflets, entire to serrulate; pinnae 3–9, opposite on the rachis, lanceolate, 10–17 × 2–8 cm, terminal pinnae entire or pinnatisect, lanceolate to ovate, 10–15 × 3.5–7.5- cm, all with apex acuminate, base decurrent-oblique, margins ciliate and serrate, shining green, glabrate, with 5–10 apiculate teeth, sometimes with petiolules 4–11 mm long; pinnules alternate on the rachilla, lanceolate, 4–8 × 1–1.6 cm, all with apex acuminate, base decurrent-oblique, margins ciliate and serrate, glabrate, with 5–8 apiculate teeth. Synflorescence corymbiform, heads (1–)15–25; peduncles 40–65 cm long, hollow, glabrescent, green-reddish and shining, central peduncle 10–19 × 0.2 cm, lateral peduncles 7–14 × 0.1–0.12 cm. Heads 6.5–10 cm wide across the extended rays. Involucre 1.5–3.5 × 2–2.5 cm, cup-shaped. Phyllaries biseriate; outer series 5, green, glabrous, reflexed at anthesis, elliptic to lanceolate, 6–9 × 3–3.5 mm, acute or rounded apex, with 5–8 light brown resiniferous ducts; inner series 8, yellow-greenish, glabrous, lanceolate, 12–18 × 3–5 mm, apex acute, with 18–22 light brown resiniferous ducts. Receptacle convex to plane, paleaceous, 5–9 mm diameter, tomentulose. Paleae translucent, bright when dehydrated, 15–17 × 7–8 mm, persistent and resembling the inner phyllaries. Ray florets 8, uniseriate, sterile, light lilac with a yellow spot at the base, limb obovate, 3–3.5 × 1.2–1.5 cm, 3–5 ribbed outside, ribs glabrescent, apices obtuse, trilobulate, tube 2.5–3 × 1–1.5 mm, glabrescent. Disk florets 31–45, yellow, funnel-shaped, 4–4.5 mm long; corolla tube 1–1.4 × 0.3–0.4 mm, glabrous; throat 0.6–0.8 mm; lobes 5, 0.4–0.5 mm long, erect, triangular. Anthers 3.5–5 mm long, light brown, apical appendages triangular, short sagittate at the base; pollen yellow. Style 5.5–7.5 mm long; stigma lobes 2–2.5 mm long, yellow, acute, penicillate, long papillate beneath and along the margins. Cypsela clavate, 6.5–9.5 × 1.5–2.4 mm, furrowed, black, glabrate, scabrous on the rounded angles, attenuate, carpopodium annular, pappus cup shaped.

Distribution, habitat and phenology:— As far as we know, Dahlia tamaulipana grows in Sierra Grande, Sierra Cucharas and Sierra Chiquita, at the south-western extreme of Tamaulipas, Mexico ( Figure 2 View FIGURE 2 ). It grows in wet ravines of oak-pine forest with riparian vegetation and cloud forest. It is associated with Beschorneria septentrionalis García-Mendoza (1988: 3) , Bocconia frutescens Linnaeus (1753: 505) , Carya illinoiensis ( Wangenheim 1787: 54) Koch (1869: 593) , Chamaedorea radicalis Martius (1849: 308) , Clethra pringlei Watson (1890: 157) , Platanus mexicana Moricand (1837: 39) , Quercus rhysophylla Weatherby (1910: 423) , and Sedum palmeri Watson (1882: 355) . It blooms and fructifies from mid-October to mid-November.

Etymology:— The specific epithet refers to its restricted geographic distribution in Tamaulipas, Mexico and to honor the people of this state.

Chromosome number:— Dahlia is cytologically variable with three basic numbers, x= 16, 17 and 18. In addition, the x= 16 group contains diploid and tetraploid species (2n= 32 and/or 2n= 64). Based on the chromosome evolution hypothesis of Gatt et al. (1999) and Murray (2008), it has been suggested that the genus emerged via paleopolyploidization, x= 17 is the ancestral condition, followed by two different events of aneuploidy. Dahlia tamaulipana is a diploid species with 2n= 2x= 32 ( Figure 3 View FIGURE 3 ). This count coincides with the chromosomal levels for most species in Dahlia sect. Dahlia .

Taxonomic relationships:— Dahlia tamaulipana develops herbaceous stems, with hollow internodes, pinnules alternate on the rachilla, petioles solid and a chromosome number 2n= 2x= 32. These characters allow us to relate this species as a member of Dahlia sect. Dahlia . If the key to the identification of Dahlia species proposed by Hansen (2007) is used, it is possible to relate D. tamaulipana with D. tubulata Sørensen (1980: 353) . However, D. tamaulipana differs from the latter species by developing stems evidently hexagonal and villous in the upper portion of the nodes and the base of the petioles (vs. cylindrical and glabrescent), the internodes reach 3–5.5 × 1–1.5 cm [vs. 5–9.5(–12) × 0.3–0.7 cm], the stipels are present from the first to the third pair of leaflets (vs. present only in the first pair of leaflets), the synflorescence develops (1–)15–25 heads [vs. (1–)2–6 heads], and the heads reach 6.5–10 cm wide across the extended rays (vs. 4.5–6 cm) ( Figures 4M, 4O View FIGURE 4 ).

Both species inhabit the northern portion of the Sierra Madre Oriental; however, they are not sympatric and do not share ecological preferences and phenological behavior ( Figure 2 View FIGURE 2 ). Dahlia tamaulipana grows in very wet ravines of riparian vegetation between oak-pine forest and cloud forest at approximately 950–1550 m of elevation, and blooms from mid-October to mid-November. In contrast, D. tubulata grows in ravines of sclerophyllous forest and coniferous forest at approximately 2100–3700 m of elevation, and blooms from early August to mid-September.

Conservation assessment: — Dahlia tamaulipana is represented by seven collections from four populations.

Based on cells of 2 × 2 km and using GeoCAT ( Bachman et al. 2011), we calculated that the Extent of Occurrence

(EOO) was 202.8 km 2, and 20 km 2 for the Area of Occupancy (AOO). Following the IUCN (2012) criteria, the results of this study allowed us to determine the Extent of Occurrence estimated to be less than 5000 km 2 and that the species occurs at no more than five locations, so that a preliminary category of Endangered is proposed (EN/B1a).

Dahlia tamaulipana is likely to be found in other locations of the Sierra Madre Oriental between the states of Tamaulipas and Nuevo Leon, an area of few botanical explorations and one of the most difficult to access in the region. We consider that it is very important that the environmental authorities of Tamaulipas declare the habitat of this species as an area of ecological value, since human activities in the extraction of mineral materials, wood and water are high risk factors for the survival of the natural patrimony. However, it is also encouraging to know that D. tamaulipana is found within El Cielo Biosphere Reserve.

Moreover, Dahlia tamaulipana is a direct source of food for the wild fauna. During our explorations we observed a group of wild turkeys [ Meleagris gallopavo Linnaeus (1758: 156) ] consuming the leaves and flowers of the species.

Additional material examined (paratypes): — MEXICO. Tamaulipas: Ciudad Victoria: km 17 de la brecha del Parque Ecológico Los Troncones hacia La Chona y El Molino , 1040 m, 23º45’14.6”N, 99º18’27.1”W, 15 September 2017 (esterile), A. Castro-Castro et al. 4355 (CIIDIR!, IBUG!, IEB!, MEXU!) GoogleMaps ; Ejido Vicente Guerrero, Cañón de la Peregrina, km 17 de la brecha del Parque Ecológico Los Troncones hacia La Chona , 1040 m, 23º45’14.6”N, 99º18’27.1”W, 8 November 2017 (fl, fr), R. Macías-Flores & L. García 27 (CIIDIR!, IBUG!, IEB!, MEXU!) GoogleMaps ; Cañón del Novillo , 1 km al norte de la mina de serpentina, 957 m, 23º43’12”N, 99º17’4”W, 14 November 2017 (fl, fr), R. Macías-Flores & L. García 54 (CIIDIR!, IBUG!, IEB!, MEXU!). Gómez Farías: predio NCPA San José, 1 km al oeste de San José rumbo a Emilio Portes Gil, camino a la Reserva de la Biosfera El Cielo, 1568 m, 23º3’1”N, 99º14’34”W, 16 November 2017 (fl, fr), R. Macías-Flores & L. García 63 (CIIDIR!, IBUG!, IEB!, MEXU!) GoogleMaps ; camino a la Reserva de la Biosfera El Cielo partiendo de Gómez Farías, 1 km al oeste de Alta Cima rumbo al Valle del Ovni , 1102 m, 23º3’21”N, 99º12’39”W, 16 November 2017 (fr), R. Macías-Flores & L. García 68 (CIIDIR!, IBUG!, IEB!, MEXU!). Jaumave: El Rancho El Cielo, 1300 m, 23º17’44”N, 99º13’43”W, 11 October 1986 (fl, fr), O. Rocha 91 (UAT!) GoogleMaps .