Commelina occulta D.Juárez, 2023

Maldonado-Moreno, Claudia, Alvarez-Jiménez, Abel De Jesús, Gutierrez, Héctor David Juárez-, Alba, Guillermo Alatorre-De & Muñiz-Castro, Miguel Ángel, 2023, A remarkable new species of Commelina (Commelinaceae) from western Mexico, Phytotaxa 612 (1), pp. 67-76 : 68-74

Commelina occulta D.Juárez sp. nov. ( Figs. 1 –3,5D)

Diagnosis:—Similar to Commelina standleyi Steyerm. but differs in having glabrous and broad leaves, axillary inflorescences, glabrous and bigger spathaceous bract, 3–4.5 × 2–3 cm and long and robust peduncles, 2.5–6.5 cm.

Type:— MEXICO, Jalisco: Tepatitlán de Morelos municipality, 5.5 km al oeste de la desviación a Las Calabazas por el camino de ascenso al Cerro del Maguey, Pastizal inducido en Selva Baja Caducifolia. Abundante en suelos anegados, 20°45’10.11”N, 102°39’29.59”W, 2020 m, 5 August 2021, D. Juárez - Gutierrez & G . Alatorre - de Alba 773 (holotype: IBUG!; isotypes: IEB!, MEXU!) .

Herb up to 70 cm tall, perennial, terrestrial, frequently paludal. Roots 30–120 × 3–5 mm, tuberous, terete. Rhizome underground, short, reddish-brown. Stems erect to ascending, succulent, rooting only at the base; internodes terete, distally longer, distal 0.5–1.5 cm long, white, proximal 1–10 cm long, green. Leaves spirally-alternate, sessile; sheaths 2–3.5 × 0.5–2 cm, glabrous; lamina 4–15 × 1–3 cm, lanceolate, oblong-lanceolate, elliptic-lanceolate or ovate-lanceolate, flat, occasionally conduplicate, fleshy, green, glabrous, base rounded to attenuated, margin scarious, apex acute, acuminate to long acuminate; terminal leaves spathaceous, occasionally glaucous, base subamplexicaulous to amplexicaulous; midvein conspicuous, adaxially impressed, abaxially obtuse, secondary veins 3–12 pairs, adaxially conspicuous, abaxially inconspicuous, becoming conspicuous on both sides when dry. Inflorescences axillary and leaf-opposed, peduncle 2.5–6.5 cm, stout, straight, glabrous; spathe 3–4.5 × 2–3 cm, depressed-ovate, turbinate, conduplicate, base connate for 12–20 mm, cordate, margin scarious, apex acute, apiculate or acuminate, veins 6–8 pairs, mucilaginous inside; upper cincinnus vestigial, included in the spathe, rarely developed, when developed similar to the lower and exserted from the spathe, peduncle 0.5–1.5 cm long, erect at pre-anthesis and anthesis, acrescent and lax at post-anthesis and fruit, glabrous; lower cincinnus 7–9-flowered, flowers hermaphrodite, peduncle 1.5– 2.5 cm long, included in the spathe, glabrous; bracteoles absent. Flowers zygomorphic, perfect; pedicels 6–13 mm long, inflected in bud, erect at anthesis, reflexed and slightly elongate in fruit, glabrous; sepals 3, free, concave, light green, hyaline, glabrous, with conspicuous green veins, dorsal sepal 5–10 × 2–4 mm, ovate to oblong-lanceolate, apex rounded to acuminate, lower sepals 5–10 × 4–7 mm, oblong-ovate to elliptic, apex rounded to acuminate; paired petals clawed, limb 1.5–2.5 × 1.5–2.5 cm, reniform to semirotund, dark blue, base cordate, margin entire to erose, apex rounded, claws 4–6 mm long, light blue, medial petal shortly-clawed, limb 1.5–2.5 × 1.5–2.5 cm, depressed-ovate to deltoid, flat to concave, concolourous with the paired petals, glabrous, claw 2–4 mm long, light blue; staminodes 3, medial staminode equal to the laterals, filaments 5–7 mm long, filiform, dark blue, antherodes 2–3 × 2–3 mm, Xshaped, yellow; lateral filaments 10–15 mm long, filiform, curved, dark blue, anthers 3–5 × 2–3 mm, ovate-lanceolate, basifixed, white, slightly shorter than the central one; medial filament 8–15 mm long, filiform, curved, shorter than the lateral ones, dark blue, anther sagittate, 4–6 × 2–4 mm, basifixed, white; ovary 1–2 × 1–1.5 mm, 3-carpellate, 5–6- ovulate, ovoid, light green to white, style 1.5–2.5 cm long, filiform, light blue to white, distally curved, stigma capitate, white to light blue. Capsule 5–9 per spathe, 6–9 × 3–4 mm, ellipsoid, 2-valved, apex shortly apiculate, dorsal locule 1-seeded, ventral locules 4-seeded. Seeds dimorphic, dorsal valve seed 3 × 2 mm, strongly adhered to the valve wall, ovoid to ellipsoid, ventrally flattened, light brown, testa smooth, embryotega semilateral, relatively inconspicuous, without a prominent apicule, hilum linear, more than ½ the length of the seed, ventral valve seeds 3 × 2 mm, free from the valve wall ovoid to oblong, truncate at one end, ventrally flattened, dark brown, testa foveolate, embryotega semilateral, relatively inconspicuous, without a prominent apicule, hilum linear, ½ the length of the seed.

Phenology:—Flowering from July to October and fruiting from September to November.

Distribution and habitat:— Commelina occulta is known from scattered localities of Ahualulco de Mercado, Ameca, San Martín Hidalgo, Tecalitlán and Tepatitlán in the state of Jalisco, in an elevational range of 1420–2030 m. Grows on flooded grasslands and the shores of water bodies in open areas of tropical dry forest and oak-pine forests with Commelina tuberosa Linnaeus (1753: 41) , Cyperus spp ., Salvia reptans Jacquin (1798: 38 , t. 319), Urochloa meziana ( Hitchcock 1908: 140) Morrone & Zuloaga (1993: 68) and Vachellia farnesiana ( Linnaeus 1753: 521) Wight & Arnott (1834: 272) .

Etymology:—The specific epithet, occulta , refers to the fact that the new species was confused for a long time with C. standleyi .

Additional specimens examined:— MEXICO, Jalisco: San Martin Hidalgo municipality, Los Barbosa (San Jerónimo) a 5 km al oeste del municipio de San Martin Hidalgo, Matorral con predominancia de leguminosas, 1800 m, 11 October 1982. J . J . Ramírez-Guerrero 2 ( IBUG). Ameca municipality, 10 km sobre la brecha de Ameca a Quila , Matorral subtropical, 1600 m, 2 October 1988. M . Cházaro - B ., J . Gutiérrez - A . & M . Rodríguez - H . 5707 ( IBUG). Tecolotlán municipality, Sierra de Quila, Quililla , 600 m al oeste, Bosque de Quercus magnoliifolia abierto al cultivo. Abundante localmente en el margen de un charco estacional, 22 October 1989. J . J . Guerrero - Nuño , B . Rubio & N . González 463 ( IBUG). Ahualulco de Mercado municipality, camino a las Piedras Bola , Bosque de pino y encino, 1 September 1995. J . J . Reynoso -D. 2943 ( IBUG). Tepatitlán de Morelos municipality, 5.5 km al oeste de la desviación a Las Calabazas por el camino de ascenso al Cerro del Maguey, Pastizal inducido en Selva Baja Caducifolia. Abundante en suelos anegados, 20°45’10.11”N, 102°39’29.59”W, 2020 m, 20 September 2022. D. Juárez - Gutierrez & A . Alvarez 775 ( IBUG) .

Notes: — It is difficult to establish the taxonomic relationships of the new species. Currently, there is no satisfactory systematic arrangement for the Mexican taxa of the genus Commelina and several of them present nomenclatural and/ or taxonomic delimitation problems ( Hunt 1993; López-Ferrari et al. 1997; Espejo-Serna et al. 2009; Hassemer 2018a, 2018b, 2019; León-de la Luz et al. 2019). However, the flowers, capsules and seeds of C. occulta suggest a relationship with the C. tuberosa complex.

Owing to their basally connate spathes, spathaceous leaves close to the inflorescences, and erect habit, C. occulta resembles C. standleyi , from which is easily differentiated by being more robust, glabrescent, having broad leaf blades, leaf-opposed inflorescences and larger spathaceous bracts (3–4.5 × 2–3 cm), glaucous, peduncle robust and 2.5–6.5 cm long, while C. standleyi is a scabrous plant with thin and linear leaves, apparently terminal inflorescences with smaller scabrid-hirtellous spathes 2–2.5 × 1–1.3 cm, and peduncles 1–2.5 cm long.

Commelina occulta could also be confused with C. erecta Linnaeus (1753: 41) , but it can be distinguished by the presence of three conspicuous, subequal petals and the absence of auricles on the leaf-sheaths as well as a mainly erect and robust habit, instead C. erecta has a greatly reduced medial petal ( Fig. 5E ), auriculate leaf-sheaths, and a generally erect to decumbent habit. The new species has dark blue flowers, a feature that can be confused with C. coelestis Willdenow (1809: 69) , a common taxon in the area. However, the glabrous and connate spathes and cylindrical tuberous roots distinguish C. occulta , while C. coelestis has hairy spathes free at base and botuliform tuberous roots.

Although Hassemer (2018a, 2019) considers that C. coelestis , C. dianthifolia Delile in Redouté (1813: t. 390) and C. jaliscana Matuda (1959: 101) are synonyms of C. tuberosa , we do not agree. Despite the fact that most of the characters that differentiate these species are vegetative, they are enough to distinguish them. On other hand, these species have a wide distribution and are usually sympatric, in addition to sharing some morphological characteristics ( C. tuberosa complex), which is often confusing. However, the key present in the work of Espejo-Serna et al. (2009) is quite useful for the determination of the species in question, in addition to the one presented here.

IUCN Threat Assessment: — According to the IUCN Red List Criteria ( IUCN 2022), C. occulta should be categorized as Endangered due to its extent of occurrence (EOO) <5,000 km 2 (B1 criterion) with severely fragmented locations [condition (a)] and an estimated continuing decline of its area of occupancy [condition (b)(ii)], and quality of habitat (iii).

Figures

FIGURE 1. Commelina occulta.A, habit. B, lateral view of the spathaceous bract, showing cincinnus and peduncular structures. C, flower, frontal view. D, dissected flower. E, fruit. F. seed.A–F from D. Juárez-Gutierrez & G. Alatorre-de Alba 773. Drawing by A. Alvarez.

FIGURE 5. Floral variation in western Mexico Commelina (continued).A, C. leiocarpa. B, C. texcocana. C, C. standleyi. D, C. occulta. E, C. erecta. F, C. rufipes var. rufipes. Photos A, C–F by D. Juárez, B by D. Figueroa.