Pinguicula warijia Zamudio, Hern.Rend., M.Mata-Rosas & M.M.Salinas, 2023

Zamudio, Sergio, Mata-Rosas, Martín, Salinas-Rodríguez, María Magdalena & Hernández-Rendón, Julián, 2023, Pinguicula warijia sp. nov. (Lentibulariaceae), a newly rediscovered species from the Sierra Obscura, northern Mexico, Phytotaxa 578 (3), pp. 219-227 : 220-226

Pinguicula warijia Zamudio, Hern.Rend., M.Mata-Rosas & M.M.Salinas , sp. nov. ( Figs. 1–2 )

Similar to Pinguicula zamudioana but differs in having numerous, sessile, spathulate to elliptic-spathulate leaves (vs. 4–8(10) petiolate, oblong–elliptical to suborbicular leaves), upper calyx lip lobes ovate to elliptic (vs. triangular-lanceolate), lower calyx lip lobes triangular (vs. lanceolate), upper corolla lip lobes suborbicular to oblate (vs. oblong–elliptical to suborbicular), capsule botuliform (vs. subglobose), seeds 1–1.28 mm long, ca. 0.2 mm wide, surface slightly reticulate (vs. ca. 0.5 mm long, ca. 0.1 mm wide, surface reticulate).

Type: — MEXICO, Chihuahua, Uruachi municipality, Arroyo Babarocos canyon near El Serruchito; June 5, 2022, S . Zamudio , M . MataRosas , M. E . Salinas & J . Hernández-Rendón 17774 (holotype: UAMIZ; isotypes: ENCB, IBUG, MEXU, UAMIZ, XAL) .

Perennial herb, homophyllous. Leaves (5)10–25, arranged in a lax basal rosette, sessile, membranous, spatulate to elliptic-spatulate, green or purple, erect or recurved, surface convex, 40–130 mm long, 13–40 mm wide, apex rounded, base attenuate, margin entire, straight, slightly involute towards apex, upper surface densely covered by small, stipitate glands, 0.2-0.25 mm long and numerous sessile glands. Peduncles 1–5 per plant, purple, erect, 60–120 mm long, tapering from 2 mm in diameter at base to 1 mm at apex, covered densely by stipitate glands 0.2-0.25 mm long, uniflorous. Flower 40–60 mm long including the spur. Calyx bilabiate, pale green, outer surface with stipitate glands and these scant on the inner surface, upper lip trilobed almost to the base, lobes ovate to elliptic, apex acute, 2.5–4 mm long, 1.2– 2.5 mm wide, lower lip 2–3 mm long, 1.5–3 mm wide, bilobed, lobes triangular, 1.2–2.5 mm long. Corolla bilabiate, pink-violet to purple, with a small white spot at the base of the lower lip or a discontinuous ring of white around the throat, outer surface sparsely covered with short glandular hairs; upper lip bilobed, lobes suborbicular to oblate, 7–12 mm long, 7–14 mm wide, overlapping at the sides, lower lip trilobed, lobes obovate-oblong to suborbicular, 8–18 mm long, 7–17 mm wide, apex rounded, the lobes overlapping or not at the base. Tube very short, infundibuliform, 3–5 mm long, 4–5 mm wide, with multicellular subulate trichomes ca 0.8 mm long, these forming a narrow band on the inner surface that extends from the throat to the tube but not into the spur; trichomes slightly swollen at the junction between the cells, tips formed of several disc-shaped cells, pointed (Lampard in Lampard et al. 2016). Spur cylindric-subulate, curved, 23–32 mm long, 1–1.5 mm wide. Stamens 2–3 mm long, filaments curved, 1.5–2 mm long, covered with short, stipitate glandular hairs, anther subspherical, ca. 1 mm in diameter. Ovary subglobose, green, 1.5–2 mm in diameter, glandular-pubescent, with short stipitate glands, stigma bilobed, pink, subsessile, lower lobe flabellate, 1–1.5 mm long, ca. 2 mm wide, larger than the upper. Capsule botuliform, 4–6 mm long, 2.5–4 mm wide, covered with short stipitate glands. Seeds numerous (362±80), ellipsoid, 1–1.28 mm long, ca. 0.2 mm wide, surface slightly reticulate.

Distribution, ecology and phenology: —So far, this plant is only known from one locality with certainty, and we are not sure if the type locality represents the same site visited by Lau in 1972.

The plant grows on the ceiling and walls of a small south-facing cave, on calcium carbonate concretions accumulated on igneous rocks with continuous water runoff ( Fig. 2 , A–C). The vegetation surrounding the cave is an ecotone of oak-pine forest and deciduous tropical forest, comprised of Acaciella sp. , Agave sp. , Bursera sp. , Ceiba sp. , Jatropha sp. , Leucaena sp. , Nolina sp. , Pinus sp. , Quercus spp. , Senegalia sp. , Yucca sp. , and various types of grasses, at an elevation of 1590–1600 m. The climate is semi-warm sub-humid, with summer rains and an average annual temperature between 18° and 24°C. The average annual precipitation is 700 to 800 mm ( CONABIO 1998). The soil on the slopes of the ravine is lithosol, with a very shallow and fragile organic matter cover ( INEGI 2014).

According to information and pictures that our guide sent to us throughout the year, this species flowers and fruits all year round. There is enough humidity in the environment to guarantee its continuous growth. However, some plants exposed to drier conditions were observed in which the leaves are significantly reduced in size without changing their shape, allowing the plant to survive short periods of drought and regrow when the humidity of the environment increases with each new rainy season. In some cases, plant size is reduced even more and rosettes are partially buried in the substrate as a form of resistance to drought ( Fig. 2 , F).

During our in situ studies of P. warijia , a two-tailed swallowtail butterfly ( Papilio multicaudata Kirby ) was observed spending considerable time visiting the flowers of P. warijia in search of nectar ( Fig. 2 , G). This fact is noteworthy because there are few records of the activity of pollinators visiting Pinguicula in nature.

Etymology: —The specific epithet honors the Warijó or Guarijó indigenous people, who inhabit this portion of the Sierra Madre Occidental in the municipalities of Chinipas, Moris, and Uruachi in the state of Chihuahua, as well as in the municipalities of Álamos, Quiriego, and Rosario in the state of Sonora. In addition, it is also the ethnic group to which our guide, Mr. Arnulfo Méndez, belongs. The word Warijó means “the people” or “the people that speak the Guarijía language”. Other names by which this ethnic group is known are Marakawe, Macoragüi, Varihio, Varohío, and warijío(a) ( Porras 1997).

Conservation status: — Pinguicula warijia is a microendemic species. The population visited was observed to be healthy, and the plants were thriving. The surface covered with plants is less than 100 m 2 and the population contains fewer than 1000 individuals. Therefore, according to the IUCN Red List (2022) used to evaluate the conservation status, P. warijia is thus capable of becoming Critically Endangered (Criteria B2ab(i, ii,v)) or even Extinct in a very short time.

Naturally, this species is affected by the periodic collapse of the cave walls and ceiling, which are very unstable due to the softening of the substrate during the rainy season caused by the excessive accumulation of humidity, so it is very probable that some plants fall and are carried away by sporadic landslides.

Taxonomic relationships:—Due to its morphological characteristics, Pinguicula warijia can be included in section Orcheosanthus de Candolle (1844: 27), in which it resembles P. oblongiloba ( Casper 1966; Burelo-Ramos et al. 2018). However, it differs from this taxon by the size and color of the flowers ( Fig. 3 B vs. H). It can be easily distinguished by having only one type of leaves (homophyllous), while P. oblongiloba forms a compact, bulbous, hypogeous winter rosette in addition to its summer leaves (heterophyllous). Other differences include the spatulate or elliptic–spatulate leaves with an attenuate base that is not differentiated into a petiole ( Fig. 1 , A and B), although Lampard et al. (2016: 686) suggest that the leaves are petiolate from observations of cultivated P. warijia , in nature the petiole of the lamina is not differentiated, while the overall leaf is spathulate to elliptic-spathulate and the surface convex (vs. oblong-elliptic to suborbicular leaves, with a clearly differentiated petiole and concave surface), calyx lobes ovate, elliptical to triangular (vs. lanceolate), corolla upper lip lobes suborbicular to oblate (vs. oblong-ovate to elliptical), corolla lower lip lobes ovate-oblong to suborbicular ( Fig. 1 , F and Fig. 2 , D) (vs. elliptical to ovateoblong); capsule botuliform ( Fig. 2 , E) (vs. subglobose); and seed surface slightly reticulate without papillae (vs. reticulate–papillate or reticulate–coliculate with long papillae) ( Fig. 3 , C vs. I). These features support and contrast the differences between both species. They also differ in the flowering season, since while P. warijia flowers throughout the year, P. oblongiloba does so from the end of May to the beginning of August. The habitat is also different; the former is located in the transition between oak-pine forest and tropical deciduous forest, at an elevation of 1590–1600 m, and the latter in a pine-oak forest at (1100–)1500–2500(–2800) m ( Table 1).

Pinguicula warijia is also similar to P. zamudioana , both being homophyllous plants that do not form a winter rosette and which flower throughout the year. However, P. warijia differs by having a greater number of leaves, with the base attenuate, margin entire, straight, slightly involute towards apex, the corolla lobes suborbicular to oblate, the greater seeds and the trichomes of the corolla tube are simple and multicellular, subulate (vs. trichomes capitated). Although the microhabitat in which they grow is similar, the locations of these species are separated by about 1000 km (in straight line), and the elevational range in which they are found is different since P. warijia is presently only known to grow at 1590–1600 m, while P. zamudioana grows at 1100–1250 m ( Table 1).

The description of this species and the recently described Pinguicula michoacana and P. zamudioana establishes a group of taxa related to P. oblongiloba , and in a lesser degree to P. orchidioides . This complex most likely is derived from a common ancestor and has evolved in western Mexico on igneous substrate in the physiographic provinces of Sierra Madre Occidental and Sierra Madre del Sur mainly ( Fig. 4 ). It is important to mention that within this group of species, P. oblongiloba and P. orchidioides have the widest ranges and according to Zamudio (1998), both are considered derived from a common ancestor that was separated by the emergence of the Trans-Mexican Volcanic Belt. Due to the prolonged geographic isolation, its populations have been gradually differentiating, each following its evolutionary path (an example of allopatric speciation).

The presence of Pinguicula michoacana , P. zamudioana , and P. warijia within the area of P. oblongiloba is noteworthy, each occurring near or very close to the lower limit of distribution of this species and occupying different microhabitats ( Fig. 4 ). Their microendemic distribution reveals an ecological isolation process and their posterior speciation from a common ancestor to grow in isothermic environments, with a constant supply of water, expressed in the occurrence of several genetic changes that led to the modification of the winter rosette in P. michoacana or even to the loss of this characteristic in P. zamudioana and P. warijia . This group of species represents a clear example of stasipatric speciation, where peripheral populations of the central population are differentiated by random genetic changes or mutations, and the differences preserved through ecological isolation until they become independent species.

With this rediscovery, the number of Mexican Pinguicula species increases to 52 ( Burelo-Ramos et al. 2018, Juárez-Gutiérrez et al. 2018, Zamudio et al. 2018, Zamudio et al. 2019, Zamudio & Nevárez-de los Reyes 2020).

The following key separates the species related to Pinguicula oblongiloba occurring in western Mexico.

1. Plants homophyllous, with a single type of leaf; blooming throughout the year ...............................................................................2

– Plants heterophyllous, with two different types of leaves (winter and summer rosette); blooming from May to August.................3

2. Leaves obovate–elliptic to suborbicular, margin involute, clearly petiolate; distributed in Jalisco ............................. P. zamudioana

– Leaves spatulate to elliptic–spatulate, margin entire, straight, or slightly involute towards the apex, attenuated base without a defined petiole; distributed in Chihuahua ............................................................................................................................. P. warijia

3. Winter rosette, with an external layer of scarious, ciliated leaves......................................................................................................4

– Winter rosette, without an external layer of scarious ciliated leaves; distributed in Michoacán ................................. P. michoacana

4. Summer leaves oblong–elliptic to suborbicular; corolla lobes oblong–ovate to elliptic; distributed in Sonora, Sinaloa, Chihuahua, Durango, Zacatecas, Aguascalientes, Jalisco, Colima, Michoacán, and Mexico......................................................... P. oblongiloba

– Summer leaves elliptic, narrowly ovate–oblong to lanceolate; corolla lobes elliptical to oblong–lanceolate; plant frequently producing stolons; distributed in Guerrero and Oaxaca in Mexico, and Sololá in Guatemala.................................... P. orchidioides

Figures

FIGURE 1. Pinguicula warijia. A. Habit with rosette, flower, fruit and flower bud. B. Leaf series with variation in size and form.C. Detail of the stipitate glands of the leaf. D. Calyx, back view. E. Flower, lateral view. F. Corolla shape variation, frontal view. G. Detail of the throat of the tube showing the multicellular trichomes and stigma. H. Trichomes of the tube. Drawing by María Teresa Jiménez-Segura.

FIGURE 2. Pinguicula warijia. A. Habitat overview. B. Plants growing on igneous rocks on a ca. 30° slope. C. Plants growing upside down on the ceiling of a small cave. D. Detail of the flower. E. Capsule. F. Plant growing in a dry area with reduced leaves. G.A two-tailed swallowtail (Papilio multicaudata) butterfly pollinating a P. warijia flower. Photos A, F and G by Julián Hernández-Rendón; B, C, D and E by Martín Mata-Rosas.

FIGURE 3. A–C, Pinguicula warijia. A. Summer rosette. B. Flower. C. Seed. D–F, Pinguicula zamudioana. D. Summer rosette. E. Flower. F. Seed. G–I. Pinguicula oblongiloba. G. Summer rosette. H. Flower. I. Seed. Photos A and B by Martín Mata-Rosas; D by David Juárez-Gutiérrez; E, G and H by Julián Hernández-Rendón; C, F and I by Greta Hanako Rosas-Saito.

FIGURE 4. Distribution map of Pinguicula warijia, and related species P. oblongiloba, P.zamudioana, P. michoacana and P.orchidioides. Map made by Abraham Ornelas-Ibarra.