Pachyphytum huastecanum is described as a new species discovered in the Cañón de la Huasteca in the Sierra Madre Oriental in the Mexican state of Nuevo León. This species is placed in section Diotostemon, where it is morphologically related to Pachyphytum hookeri, from which it differs by its shorter stems, compact rosettes, flat, olive-green colored leaves, shorter pedicels, its campanulate flowers and obovate petals. Additionally, two DNA diagnostic nucleotides were found at the ITS2 nuclear genome region which differentiate the new species from other 19 Pachyphytum species.
Introduction
In March 2016, Michael Bechtold and Wolfgang Metorn, German enthusiasts of the Agavaceae family, visited El Pajonal in the Huasteca Canyon to search for Agave albopilosa I. Cabral, Villareal & A.E. Estrada. Looking for more plants of this rare species they wandered along the Arroyo Potreritos where they found a species of Pachyphytum Link, Klotzsch & Otto. They sent pictures of the plants to Julia Etter and Martin Kristen, editors of the Crassulaceae database website ( www.crassulaceae.com). The specimens resembled P. hookeri A. Berger, however, that species occurs about 370 kms south of El Pajonal as the crow flies. It was not until November 2016 when Julia Etter and Martin Kristen, searching for species of the Crassulaceae family, and particularly those belonging to the genus Echeveria, went to the Huasteca Canyon to collect this new species of the genus Pachyphytum, along with P. werdermannii Poelln., the northernmost known to date. Plants were not flowering at this time of the year and living plant material was sent to the facilities of the Botanical Garden of the Biology Institute of Universidad Nacional Autónoma de México (UNAM), specifically to the greenhouses known as National Laboratories of Biodiversity (Laboratorio Nacional de Biodiversidad (LANABIO)), where almost all Pachyphytum species are also sheltered.
The plants produced flowers in March 2018 and after a thorough comparison with related Pachyphytum species, morphological diagnostic characters for this new species were found. At the same time, DNA sequences of rbcL and matK of the chloroplast genome, and ITS2 region from the nuclear genome were obtained for one Pachyphytum huastecanum specimen and then compared with sequences of P. brachetii J.Reyes, O.González & A.Gutiérrez, P. bracteosum Link, Klotzsch & Otto, P. brevifolium Rose, P. caesium Kimnach & Moran, P. compactum Rose, P. contrerasii Pérez-Calix, I.García & Cházaro, P. fittkaui Moran, P. garciae Pérez-Calix & Glass, P. glutinicaule Moran, P. hookeri, P. kimnachii Moran, P. longifolium Rose, P. machucae I.García, Glass & Cházaro, P. oviferum J.A.Purpus, P. rzedowskii I.García, Pérez-Calix & J.Meyrán, P. saltense Brachet, Reyes & Mondragón, P. viride E.Walther, P. viscidum J.Reyes & L.E.Cruz-López (described in 2019) and P. werdermannii. The sequences of the aforementioned 19 Pachyphytum species were previously generated to build a DNA barcoding library in collaboration with the University of Guelph and Barcode Of Life Data Systems ( www.boldsystems.org) in 2008. At that time, P. confusum Pérez-Calix, Guadián-Marín & I. García, P. neglectum J.Meyrán, and P. rogeliocardenasii Pérez-Calix & R.Torres had not yet been described and therefore were not sampled.
A table with the diagnostic nucleotides of Pachyphytum species accompanied the description of P. viscidum in a character-based approach (Reyes et al, 2019) and is updated here to include P. huastecanum. For details of DNA extraction, sequencing and methods for the analysis of the sequences see Reyes et al (2019).
Pachyphytum huastecanum J. Reyes, Etter & Kristen sp. nov.
Pachyphytum huastecanum, P. hookero (Salm-Dyck) Berger affiniis sed caulibus brevibus, foliis oblanceolatis, applanatis, (vs. caulibus longis, foliis oblanceolatis fusiformibus), rosulis laxis (vs. compactis) pedicellis usque ad 1 mm longis (vs. pedicellis usque ad 37 mm), petalis roseo-purpureis (vs. luteo-rubentibus), squama rosea (vs. lutea) differt.
Plant perennial, suffrutescent, erect, succulent, roots fibrous (Fig. 1). Stems much branched near the base, 5–10 cm long and 1–1.5 cm thick at the base (Fig. 2). Rosette dense, 8–10 cm in diameter (Fig. 3). Leaves ascending, 4–6 cm long and 1–1.5 cm wide, oblanceolate, flat to slightly concave, olive-green to bluish-green colored, somewhat farinose, margin entire, apex acute, hyaline and reddish (Fig. 4). Axillary floral stem close to the apex of the branches, 30–40 cm long, ca. 5 mm thick at the base, faint green to reddish, ascending to pendant. Inflorescence a cincinnus, pink colored, with 13–20 flowers; bracts readily deciduous, ascending, oblanceolate, spurred at the base, 10–15 mm long, ca. 5 mm wide, green to pink-green; floral bracts 5–10 mm long and 3–5 mm wide, lanceolate, green to pink-green, base spurred, somewhat pruinose (Fig. 5). Pedicels 5–10 mm long, ca. 1 mm thick, faint rose colored, farinaceous. Calyx 5 unequal sepals, joined at the base, segments oblong to lanceolate, the smaller ones 4.5–6 mm long and 2–3 mm wide, lanceolate, the larger ones 6–6.5 mm long and 3.5–4.5 mm wide, oblong, pale green, apex acute. Corolla campanulate, petals 5, erect, 10–12 mm long and 4–5 mm wide, apex mucronate, faint rose colored near the base and purplish-pink from the thickest part to the apex, appendices flattened, amorphous, faint rose color. Stamens 10, 5 antisepalous filaments 6.5–7 mm long, 5 antipetalous filaments 3.5–4 mm long, anthers yellow. Nectary scales oblong, ca. 1 mm long, yellowish. Ovary ovoid ca. 6 mm long and 4 mm wide, faint yellow to greenish, style ca. 2 mm long, purple colored, stigma greenish. Fruit, a polyfollicle.
Type: Mexico, Nuevo León: municipality of Santa Catarina, Arroyo Potreritos, near El Pajonal, Cumbres de Monterrey National Park, 1690 m. 7 November 2016. J. Etter & M. Kristen 4185 (Holotype: MEXU!).
Phenology: Plants flower from March to April in habitat and in the greenhouse.
Distribution and Habitat: Pachyphytum huastecanum is a micro-endemic species. Because of the rugged topography of the area and the resulting difficulty for thorough exploration, it is very possible that its distribution is much wider (Figs. 6 & 7). Associated species are Echeveria simulans Rose, Sedum palmeri S. Watson, Sedum calcicola B.L. Rob. & Greenm., Sedum nanifolium Fröd., Agave aff. ovatifolia G.D. Starr & Villarreal, Opuntia cantabrigiensis Lynch, Echinocereus viereckii Werderm., Dasylirion berlandieri S.Watson, Tillandsia usneoides (L.) L. Close to the site in the Arroyo Potreritos flows a seasonal creek in a forest of Quercus sp and Juniperus sp.
Etymology: The specific epithet is a reference to the Huasteca region in the state of Nuevo León, Mexico.
Discussion
Pachyphytum huastecanum is placed in sect. Diotostemon (Salm-Dyck) E. Walther by having sub-equal sepals, these shorter than the corolla (Figs. 8 & 9), and by the absence of red spots on the inner face of the petals (Fig. 10). Because of leaf shape and the pinkish petals, the new species is morphologically related to P. fittkaui, P. glutinicaule, and P. hookeri. From P. hookeri, the new species can be differentiated by its thinner and flat vs. cylindric-fusiform leaves, the color of the leaves (olive-green vs. green, bluish-green to bluish-gray), pale green and wider vs green to red sepals, by its strongly campanulate, wider vs tubular to slightly campanulate flowers, and by its shorter (10–12 mm vs 8–15 mm) obovate vs. oblanceolate petals. Pachyphytum huastecanum can be differentiated from P. glutinicaule because its stems are not glutinous and by having olive-green vs. grayish-blue colored leaves. Finally, the new species can be distinguished from P. fittkaui by its shorter stems and leaves (Table 1), its shorter and wider sepals vs. narrowed as long as the corolla sepals (sepals to petals ratio: Moran, 1971), and by its obovate vs. deltoid-lanceolate petals.
Table 1.
Morphological comparison between Pachyphytum huastecanum and related Pachyphytum species.
Table 2.
Molecular diagnostic sites summary for Pachyphytum huastecanum and another 19 Pachyphytum species.
From a DNA barcoding character-based perspective (DeSalle et al., 2005; Goldstein & DeSalle, 2011), P. huastecanum can be distinguished from other 19 Pachyphytum species — including P. fittkaui, P. glutinicaule, and P. hookeri — by the presence of the nucleotides G (Guanine) and C (Cytosine) at the sites 271 and 296, respectively, of the ITS2 genome region, in contrast to the A and G present in the sequences of the rest of the Pachyphytum species sampled (Tables 2 & 3). Additionally, the new species is geographically isolated by the mountain ranges of the Sierra Madre Oriental becoming the northernmost species known to date, and is only known in the municipality of Santa Catarina (Map 1). Specifically, it is found in the Parque Nacional Cumbres de Monterrey which encompasses more than 183,000 hectares, meaning that the species is legally protected as it occurs in a National Protected Area (Áreas Nacionales Protegidas) (Comisión Nacional de Áreas Naturales Protegidas, 2006).
Table 3.
GenBank accession numbers for the taxa sampled.
Acknowledgments
The authors would like to thank the Sociedad Mexicana de Cactología, A.C. for the arrangement of the federal collecting permit: Oficio Núm. SGPA/ DGVS/02365/17, as well as the National Laboratory of Biodiversity (Laboratorio Nacional de Biodiversidad (LANABIO) of the National Council of Sciences and Technologies ((Consejo Nacional de Ciencia y Tecnología (CONACYT)). We also express our gratitude to Omar González Zorzano for the Latin diagnosis. Julia Etter and Martin Kristen would also like to thank Michael Bechtold and Wolfgang Metorn for their patient companionship on several field trips.
