Coutaportla lorenceana Torr.- Montufar , H.Ochot. & Art.Castro, 2023

Torres-Montufar, Alejandro, Flores-Olvera, Hilda, Avila-Gonzalez, Heriberto, Castro-Castro, Arturo & Ochoterena, Helga, 2023, An assessment of Coutaportla (Chiococceae, Rubiaceae) with the description of a new species from Mexico, Plant Ecology and Evolution 156 (1), pp. 3-12 : 3

Coutaportla lorenceana Torr.- Montufar, H.Ochot. & Art.Castro sp. nov.

Figs 1 , 2

Chiococca grandiflora Lorence & T.Van Devender, pro parte ( Lorence et al. 2018: only paratypes cited on page 76: T. Walker s.n. (ARIZ-212520), S. Walker s.n. (UTC-00263027; ARIZ-181630); S. Walker 70,043 (K); see Notes).

Type.

MEXICO • Sinaloa, Municipio: Concordia. El Palmito, alrededores del acceso principal al Santuario Chara Pinta ; 23.56444°N, 105.848882°W; 1980 m; 10 Sep. 2019; fl.; Castro-Castro, Ávila-González. & Zavala-Pérez 4532; holotype: MEXU; isotype: CIIDIR, FCME, FESC, IEB, IBUG, MO, PTBG, SLPM .

Diagnosis.

Coutaportla lorenceana differs from all the other species in the genus by the lavender corollas, the apical ovule placentation, and the capsules with 1-seeded locules. It most closely resembles C. ghiesbreghtiana (Baill.) Urb. by the treelet habit and leaf size and shape, but it differs by the leaves acuminate at the apex (vs apiculate in C. ghiesbreghtiana ), the chartaceous leaf blades (vs subcoriaceous in C. ghiesbreghtiana ), the 3-9-flowered inflorescences (vs solitary flowers in C. ghiesbreghtiana ), and the lavender corollas (vs white in C. ghiesbreghtiana ).

Description.

Treelets 2-4 m tall. Twigs glabrous, greenish-brown, terete, striated; apical twigs resinous. Stipules rigid, broadly deltoid, 1.8-2.3 × 2-3.8 mm, acuminate at apex, basally connate, externally glabrous, internally with resinous colleters. Leaves petiolate, those of the same pair equal to subequal; petioles glabrous, 8-17 mm long, adaxially flat, distally winged; blades elliptic to elliptic-lanceolate, 1.3-5.8 × 0.8-1.4 cm, attenuate at base, acuminate at apex (acumen up to 1 cm long), chartaceous, matte and glabrous on both sides, concolorous; venation brochidodromous, 4-6 pairs of secondary veins on each side of midrib; domatia absent. Inflorescence axillary or rarely terminal on lateral branches, cymose, 3-9 flowered, 2.3-3.5 cm long (including the corollas); peduncles 0.2-1.4 cm long; bracts triangular, 1.3 × 0.5 mm. Flowers 4(-5)-merous; pedicels 1-4 mm long; hypanthium obconical, laterally flattened, 1-2 mm long. Calyx tube 0.4 mm long, lobes equal, subulate, rigid, erect, 1-1.5 × 0.3-0.4 mm, colleters absent. Corolla infundibuliform, lavender, tube 1.7-2.5 cm long, 0.7-0.9 cm wide at mouth, externally and internally glabrous; lobes narrowly imbricate in bud, triangular. Stamens 1.8-2.7 cm long; filaments puberulent; anthers linear. Style 2.3-2.8 cm long, glabrate. Ovules apically inserted. Capsule oblate, 4-5 × 4-5 mm. Seeds one per locule, thin, discoid, 3 × 1.2 mm, brown; testa granulate.

Distribution and habitat.

Endemic to Mexico. Only known from the oak-pine forest in El Palmito, Sinaloa state, on rocky slopes, in the Tropical Madrean Region ( González-Elizondo et al. 2012) of the Sierra Madre Occidental (Fig. 3 ), where the predominant climate is temperate-subhumid, with rains in the summer and a marked dry season in the late spring. It occurs about 1950 to 1980 m a.s.l. The only known population consists of numerous individuals associated with Agave inaequidens subsp. barrancensis Gentry, Arbutus tessellata P.D. Sørensen, Calliandra houstoniana (Mill.) Standl., Montanoa leucantha subsp. arborescens V.A.Funk, Muhlenbergia spp., Opuntia sp., Pinus herrerae Martínez, P. lumholtzii B.L.Rob. & Fernald, Quercus candicans Née, Q. scytophylla Liebm., Tithonia calva Sch.Bip., and Vachellia pennatula (Schltdl. & Cham.) Seigler & Ebinger.

Phenology.

Flowering in September and fruiting in October and November.

Etymology.

The specific epithet is dedicated to David Lorence, who has immensely contributed to the knowledge of Mexican Rubiaceae , establishing for the first time an enviable collection for the family at MEXU, which serves as an invaluable basis for research.

IUCN conservation assessment.

The species is given a Red List status of Critically Endangered [CR B1a+b(iii); B2a+b(iii)]. Coutaportla lorenceana is known from three collections, representing three occurrences, at relative proximity around El Palmito in Mexico. The extent of occurrence (EOO) is of 0.76 km2 and the area of occupancy (AOO) is of 8 km2. Both EOO and AOO fall within the limits of the Critically Endangered (CR) category under subcriteria B1 and B2. Since this species occurs at a single location and is threatened by logging and agricultural encroachment, it meets the conditions for the CR category.

Additional material examined (paratypes).

MEXICO • Sinaloa: Municipio: Concordia, El Palmito, km 201 de la Carretera Durango-Mazatlán; 23.566917°N, 105.84525°W; 1966 m; 6 Nov. 2020; fr.; Castro-Castro, Ávila-González & González-Gallegos 4695; CIIDIR, FCME, FESC, MEXU • Ca 2 km al N de El Palmito; 1955 m; 24 Oct. 2017; fr.; Torres-Montúfar, Morales-García & Castro-Castro 987; ENCB, FESC, MO, PTBG.

Notes.

Lorence et al. (2018) described Chiococca grandiflora Lorence & T.Van Devender and included as paratypes some collections from El Palmito, Sinaloa (S. Walker s.n. (UTC-00263027, ARIZ-181630), T. Walker s.n. (ARIZ-212520), S. Walker 70,043 (K)), while the holotype was collected from Sonora (P.S. Martin et al. s.n. (ARIZ-309922)), on the Pacific slope of the Sierra Madre Occidental. The holotype is vegetatively quite similar to C. lorenceana by the stipule and leaf morphology, but the two species differ by the number of flowers per inflorescence (solitary to 3-flowered in C. grandiflora vs 3- to 9-flowered in C. lorenceana ), flower merosity (always 5-merous in C. grandiflora vs 4-merous to rarely 5-merous in C. lorenceana ), flower colour (white in C. grandiflora vs lavender in C. lorenceana ), and mature fruit texture (fleshy in C. grandiflora vs dry in C. lorenceana ). We consider that the paratypes of Chiococca grandiflora from El Palmito belong in C. lorenceana , and therefore, the former species is considered a synonym pro parte. Our observation is supported by Lorence et al. (2018) who highlighted some differences among the holotype and the paratypes: the flower density being the most evident, as well as the corolla merosity and colour, clearly lavender in the specimens from El Palmito (e.g. S. Walker s.n. (UTC-00263027)).

Figures

Figure 1. Coutaportla lorenceana. A. Flowering branch. B. Detail of the venation on the abaxial leaf surface. C. Stipule and immature fruiting branch. D. Inflorescence. E. Flower. F. Ovary and calyx longitudinally dissected. G. Dissected corolla. H. Androecium. I. Detail of the puberulent filaments. J. Style. K. Capsule longitudinally dissected showing seed attachment. L. Seed. Drawn by Albino Luna (A-J, from A. Castro-Castro et al. 4532; K-L from A. Castro-Castro et al. 4695).

Figure 2. Coutaportla lorenceana. A. Habit. B. Twigs showing intrapetiolar persistent stipules. C. Flowering branch. D. Inflorescences showing corolla shape and colour. E. Longitudinal section of the ovary showing apical placentation in lateral (perpendicular to the fruit compression plane) and frontal (parallel to the fruit compression plane) views. F. Immature fruits. Photographs by Arturo Castro-Castro (A-D, F) and Helga Ochoterena (E).

Figure 3. Single known locality of Coutaportla lorenceana (red circles) in the Sierra Madre Occidental.