Tigridia mortonii Molseed (1970: 61)

Rodríguez, Aarón, Szeszko, Dennis & Munguía-Lino, Guadalupe, 2020, The species of Tigrideae (Iridaceae) in the Sierra of Nanchititla, State of México, Mexico, and description of the new species Tigridia nanchititlensis, Phytotaxa 446 (5), pp. 268-280 : 276-277

Tigridia mortonii Molseed (1970: 61)

Type: — MEXICO. State of México: Cliffs, Nanchititla , District Temascaltepec , 27.VIII.1934, G.B. Hinton 6527 (holotype US!; isotypes GBH!, GH!, K!, MO!, NY!) ( Fig. 4 ).

Description: —Bulbous, perennial, terrestrial and erect herb, 10–50 cm tall; bulb ovoid, 2.5–5 × 0.9–2.5 cm, the outer tunics thin, dark brown; scape once branched, 2–36 cm tall; basal leaves 2, linear, plicate, 40 × 0.5 cm, longer than the scape at anthesis; cauline leaves 1, linear, plicate, 6–49 × 0.06–0.6 cm; rhipidium with subequal spathe valves, 2–3 × 0.4–0.6 (0.9) cm; peduncle 1–2.5 × 0.06–0.14 cm; pedicels linear, 1.2–4 cm long; flowers 3 to several per rhipidium, erect, 2.5–3.5 cm wide; tepals connivent into a crateriform cup at the base; outer tepals ovate to elliptic, attenuate, obtuse to apiculate, 2–2.3 × 1.2 cm; inner tepals hastate, unguiculate, acuminate, 1 × 0.8 cm; tepal color varies from yellow (green-yellow group 1A, Royal Horticultural Society 2015) to red (red group 45B, Royal Horticultural Society 2015); nectary in a groove across the middle of the inner tepal, reniform, 0.05–0.14 × 0.5–0.8 mm; filaments connate, 5–6 mm long; anthers spreading, 4 mm long; ovary clavate, 0.3–0.6 × 0.08–0.2 mm; style branches 4 mm long, bifid into falcate arms; mature capsules ovoid to clavate, 1.2 cm × 5 mm; seeds globose, 1.7–2 × 2–2.1 mm.

Distribution, ecology and phenology: — Tigridia mortonii is only known from Sierra of Nanchititla ( Fig. 1 ). It grows in open areas within the OPF, between 1550–1950 m a.s.l. Bletia gracilis , Calochortus spatulatus , and Tigridia meleagris share the habitat with T. mortonii . Locally, the population is numerous. The flowers open in the morning and close early in the afternoon. It blooms from early July to August and the capsules mature from October to November.

Conservation assessment: — Tigridia mortonii is known from two populations that occupy 24 stands ( Fig. 1 ). The EOO was 9,464 Km 2 and 8 Km 2 for the AOO. Both estimated values were less than 100 Km 2 and 10 Km 2, respectively. Based on the IUCN (2019) criteria, a preliminary assessment as Critically Endangered is proposed (CR, B1 and B2) for it.

Eponymy: —This species was named after Conrad V. Morton (1905–1972), a botanist and authority on ferns. He was a senior botanist of the Smithsonian Institution and a scholar of Tigridia . On Hinton 6527 herbarium tags, Morton indicated this taxon was undescribed.

Specimens examined: — MEXICO. State of México: Luvianos, Sierra de Nanchititla , 1650 m, 8.IX.1954, E. Matuda et al. 31574 (CODAGEM, MEXU) ; Luvianos, Sierra de Nanchititila , 1565 m, 18.VIII.1974, C.V. Chávez- Tapia s.n. ( FCME) ; Luvianos, Criadero de Fauna Silvestre Nanchititla , 1600 m, 6.VIII.1991, L. Abundiz 738 ( MEXU) ; Luvianos, Parque Estatal Sierra de Nanchititla , 300 m antes de llegar a la cascada, 18°49ʼ32.82ˮN, 100°25ʼ13.79ˮW, 1531 m, 20.VII.2009, D. Szeszko s.n. ( IBUG, MEXU) ; Luvianos, Parque Estatal Sierra de Nanchititla, camino a la cascada, entre Mesas de las Riatas y la cascada, 18°50ʼ2.06ˮN, 100°25ʼ14.32ˮW, 1554 m, 27.VII.2010, A. Rodríguez et al. 6074 ( ENCB, IBUG, IEB, MEXU, MO, UAMIZ) ; Luvianos, Parque Nacional Sierra de Nanchititla , casi llegando a la cascada, 18°50ʼ15.1ˮN, 100°25ʼ18.7ˮW, 1607 m, 6.VIII.2011, G. Munguía-Lino & L.M. Vázquez-García 34b ( IBUG) ; Luvianos, Parque Nacional Sierra de Nanchititla , a mitad del camino que va hacia la cascada, 18°50ʼ14.8ˮN, 100°25ʼ15.3ˮW, 1609 m, 6.VIII.2011, G. Munguía-Lino & L.M. Vázquez-García 37 ( IBUG) ; Luvianos, Sierra de Nanchititla en la brecha a Torrecillas , 18°52ʼ35.9ˮN, 100°19ʼ48.5ˮW, 1950 m, 4.VIII.2012, G. Munguía-Lino & L.M. Vázquez-García 185 ( IBUG) ; Luvianos, Sierra de Nanchititla en la brecha a Torrecillas , en dirección a los monolitos, 18°52ʼ29.6ˮN, 100°19ʼ47ˮW, 1924 m, 4.VIII.2012, G. Munguía-Lino & L.M. Vázquez-García 187 ( IBUG) ; Luvianos, Parque Estatal Sierra de Nanchititla , rumbo a la casacada, 18°49ʼ39.7ˮN, 100°25ʼ17.5ˮW, 1549 m, 4.VIII.2012, G. Munguía-Lino & L.M. Vázquez-García 188 ( IBUG) ; Luvianos, Sierra de Nanchititla, aproximadamente 1 km al SO del paraje conocido como Torrecillas , 18°52ʼ33.9ˮN, 100°19ʼ48ˮW, 1943 m, 20.VIII.2013, G. Munguía-Lino & L.M. Vázquez-García 251 ( IBUG) .

Taxonomic remarks: — Tigrida mortonii has red or yellow tepals, a characteristic shared by only few species of Tigridia . Tigridia flammea ( Lindley 1840: 16) Ravenna in Prance & Elias (1977: 259), T. immaculata (Herb. in Lindley 1841: 68) Ravenna in Prance & Elias (1977: 260), T. inusitata ( Cruden 1971: 222) Ravenna in Prance & Elias (1977: 260), and T. orthantha (Lemaire in Lemaire et al. 1845: 251) Ravenna in Prance & Elias (1977: 260) all have red flowers, but in contrast to T. mortonii , they all show a hummingbird pollination syndrome. On the other hand, T. chrysantha , T. dugesii , and T. mexicana subsp. mexicana Molseed (1970: 54) have yellow tepals and are pollinated by bees. The flowers of T. mortonii are erect and most likely are pollinated by wasps or bees ( Munguía-Lino et al. 2017). Rodríguez & Ortiz-Catedral (2001) reported the presence of T. mortonii in the states of Jalisco and Nayarit, based on plants with red tepals collected in these states. However, a close comparison between plants collected in Nanchititla and those from Jalisco and Nayarit indicates the existence of two different species. After our analysis, we concluded that plants from Jalisco and Nayarit belong to T. chrysantha . In T. mortonii , the spathe is made of two bracts in contrast with T. chrysantha which has three bracts. The fruit of T. mortonii was unknown, but plants collected by Rodríguez et al. 6074 and G. Munguía-Lino & L.M. Vázquez-García 34 have capsules which were used for its description.

Tigrideae in the Sierra of Nanchititla: — Tigridia mortonii and T. nanchititlensis are endemic to the Sierra of Nanchititla. Other Tigrideae recorded from the Sierra include Cardiostigma longispatha (Herb. in Bentham 1839: 53) Baker (1877: 102), Cipura campanulata Ravenna (1964: 51) , T. meleagris , and T. pavonia ( Figs. 1 and 5 ; Table 2).

Endemism in the Sierra of Nanchititla: —Our findings contribute to the endemicity value of the Sierra of Nanchititla. The Mexican angiosperm flora totals 22,126 species ( Villaseñor 2016) and approximately 50.4% are endemic to the country ( Villaseñor & Ortiz 2014). Furthermore, by analyzing the distribution of 476 Mexican monocots and geophytes, Cuellar-Martínez & Sosa (2016) found that 344 species are endemic to Mexico. They also documented the Transmexican Volcanic Belt and the Sierra Madre del Sur as the species richest provinces, with 159 and 119 species, respectively. The Balsas Basin lies in between these two provinces and registered 77 species. Interestingly, Cuéllar-Martínez & Sosa (2016) mapped the species richness within the Mexican territory using grid cells of 1 × 1 Km, and the species richest grid cell, with a total of 60 species, mostly coincides with the Sierra of Nanchititla area. In a follow up study, Sosa & Loera (2017) evaluated the species richness (SR) and weighted endemism (WE) of 507 geophyte Mexican species. Again, the very same cell had the highest WE value in Mexico. Using the endemicity analysis (EA) on 766 Mexican species, Munguía-Lino et al. (2016) and Rodríguez et al. (2018) recovered areas of endemism that overlap with the Sierra of Nanchititla. According to Sosa & Loera (2017), the irregular topography and seasonality explained the high endemic rate. Here, we recorded Tigridia mortonii and T. nanchititlensis as species endemic to the Sierra of Nanchititla. Other taxa with the same restricted range are Salvia semiscaposa Epling ex Fragoso & Mart. Gord. in Fragoso-Martínez et al. (2015: 61) and Lycianthes starbuckii Dean (1994: 324) .

Figures

FIGURE 1. Distribution map of the Tigrideae in the Sierra of Nanchititla, State of México.

FIGURE 4. Tigridia mortonii. A–C. Flower. D. Habitat. Photographs: Guadalupe Munguía-Lino.

FIGURE 5. Tigrideae in the Sierra of Nanchititla, State of México. A. Cardiostigma longispatha. B. Cipura campanulata. C. Flower lateral view of Tigridia meleagris. D–E. Flower frontal view of T. meleagris. F. T. pavonia. Photographs: Aarón Rodríguez (C–E), Georgina Vargas-Amado (F), Guadalupe Munguía-Lino (A–B).