Forestiera veracruzana Cast., 2021

Palacios-Wassenaar, Olivia M. & Castillo-Campos, Gonzalo, 2021, Forestiera veracruzana (Oleaceae), a new species from the riparian forests of central Veracruz, Mexico, Phytotaxa 512 (3), pp. 190-196 : 192-195

Forestiera veracruzana Cast. -Campos & Pal.-Wass., sp. nov. ( Fig. 2 )

Type: MEXICO. Veracruz: Municipality of Actopan, Caño Gallego , 19°32’12.92”N, 96°23’22.40”W, 12 m, 19 January 2021, O . Palacios- Wassenaar , G . Castillo-Campos , & I . Acosta R . 965 (holotype XAL!; isotypes ENCB!, MEXU!) .

This taxon shows similarities with F. corollata , F. isabeliae and F. rhamnifolia and grows under similar ecological conditions in some municipalities of the Mexican states of Veracruz and Tabasco. However, F. veracruzana differs from the other two species in its polygamodioecious condition, the longer peduncle, the length and shape of pistil at anthesis, the presence of 1–2 styles, and its generally bilobed stigma ( Table 1).

Geographic distribution and ecology:— Forestiera veracruzana is part of the tree and shrub strata of riparian forests (sensu Rzedowski, 2006); and is sometimes present in seasonally flooded evergreen tropical forests, deciduous tropical forests, semi-evergreen tropical forests, palm tree forests (sensu Miranda & Hernández-X, 1963), and shrublands, both primary and disturbed. It generally grows on sandy soils at elevations between 5 and 350 m.

Trees or shrubs up to 12 m in height; polygamodioecious. Trunk subcylindrical, with whitish brown, verrucose, scaly bark; trunks and main branches with thorny-like branchlets, up to 30 cm long, usually leafless; branches with whitish orbicular lenticels, 0.2–0.5 mm in diameter; young branches decussate, striate, with reddish-brown lines; recent basal shoots greenish brown, with multiple lenticels; terminal branches short and sparsely puberulent, glabrescent; non-reproductive terminal branches bear 1 or 2 yellowish, scaly buds, 2–3 mm long in leaf axils. Leaves opposite, simple, elliptical to slightly obovate, (5–)6–13 × (2–)3–5(–6.5) cm; margin subrevolute, sparsely dentate to crenate in the distal half or third, conspicuously serrate in leaves of recent sprouts; apex acute to shortly acuminate, occasionally obcordate, acumen up to 5 mm; base cuneate to slightly attenuate, decurrent; blade smooth, glabrous adaxially, with scattered white crystals abaxially; midrib scarcely canaliculate adaxially, prominent abaxially, greenish yellow, sparsely puberulent on recent leaves; primary venation brochidodromous, yellowish green, (5–)7–11 pairs, conspicuous and slightly canaliculate adaxially, inconspicuous abaxially; tertiary venation reticulated, inconspicuous adaxially, dark green abaxially; petioles (7–) 9–13 mm long, canaliculate, occasionally semi-terete, glabrous, articulate. Inflorescences racemose, axillary, supraxillary, with (2–)3–6 pairs of basal bracts, sessile, imbricate, decussate, carinate, adaxially convex, deltoid, 1–2.5 × (0.8–) 1–2 mm; margin sparsely ciliate, erose, sometimes entire; apex acute; with 7–15 flowers in decussate pairs, the terminal section with three flowers, the central bractless, the others subtended by a foliaceous bract, obovate, adaxially concave, 2–3.5 × 1.4–2.5 mm; margin generally ciliate, sometimes erose; apex rounded, occasionally acute; base pericladial or clasping; deciduous; peduncle, rachis, and pedicels cylindrical, glabrous; pedicels articulate at the base. Female inflorescences in groups of 1 to 3, lemon green to yellowish green, (5–) 6–11 mm long, with 7–15 flowers; peduncle 0.7–1.5(–3.5) mm long; pedicels 0.5–1 mm long, frequently with a linear bracteole 0.5–1.3 mm long in the middle of the pedicel; sepals 4, free, subulate, markedly uneven, 0.4–1.2 × 0.1–0.2 mm, margin entire, apex acute, glabrous; petals 4, alternisepalous, free, oblanceolate, 1.5–3 × 0.2–0.4 mm, moderately involute, margin entire, apex rounded, glabrous, deciduous; staminodes absent; pistil 2–2.5 mm long; ovary sessile, bilocular, green, spheroid, 0.6–1 × 0.5–1 mm, glabrous, apical placentation; ovules 2 per locule, obovoid, compressed, 0.3 × 0.2 mm, styles 1–2, occasionally bifurcate from mid-length, 1–1.5 mm long, glabrous; stigma slightly or conspicuously bilobed, rarely claviform, 0.3–0.5 mm long. Male inflorescences solitary or in pairs, (8–) 14–20 mm long, with (10–)15 flowers; peduncle 1.5–2 mm long; pedicels 0.5–1.5 mm long; sepals 4–5, free, subulate, moderately unequal, 0.5–1.5 × 0.1–0.2 mm, margin entire, apex acute, glabrous; petals 4, alternisepalous, free, oblanceolate to linear, (2.5–)3–5.5 × 0.2–0.4 mm, moderately involute, margin entire, apex rounded, glabrous, deciduous; stamens 4–6, filaments 3.5–6 mm long; anthers basifixed, dithecal, with longitudinal dehiscence, elliptical to ovate, 0.5–0.8 mm long. Inflorescences with functionally hermaphroditic and staminate flowers, solitary, 15–20 mm long, with 11–13 flowers either hermaphroditic or hermaphroditic and staminate alternating along the rachis; peduncle 2.5–3 mm long; pedicels 3–3.5 mm long; sepals 4, 0.6–1.5 mm long; petals deciduous, style 1–1.2 mm long; stigma bilobed, 0.5 mm long. Infructescences 1–2 per axil, 2–3 cm long; pedicels 2.5–5 mm long; rachis subtetragonal, sparsely puberulent, with 2–10(–12) drupes, green when immature, purple at maturity, white dotted, ellipsoid, sometimes slightly falcate, 8–15 × 4.5–6 mm; apex acute, rarely rounded; base acute; style persistent, 1.2–1.8 mm long; mesocarp 1–2.5 mm thick; putamen striated. Seeds 1, rarely 2, ellipsoid, 6–7 × 3–3.5 mm.

The prevalent climate in such forests is Aw (tropical with summer rains) ( Koeppen 1948, Rzedowski 2006), with mean annual precipitation between 300 and 1800 mm, five to eight dry months over the year, and mean annual temperature of 20–29° C ( Rzedowski 2006).

Adult individuals of this newly described taxon are up to 12 m in height, forming part of the upper tree stratum (15–35 m) together with Attalea butyracea (Mutis ex L. f.) Wess. Boer ( Arecaceae ), Bambusa amplexifolia (J. Presl) Schult. f. ( Poaceae ), Bumelia celastrina Kunth (Sapotaceae) , Ficus insipida Willd. (Moraceae) , Ginoria nudiflora (Hemsl.) Koehne (Lythraceae) , Inga vera Willd. (Fabaceae) , and Tabebuia rosea (Bertol.) DC. (Bignoniaceae) . They share the middle tree stratum (5–15 m) with Bursera simaruba ( L.) Sarg. ( Burseraceae ), Coccoloba humboldtii Meisn. (Polygonaceae) , Cupania dentata DC. (Sapindaceae) , Guazuma ulmifolia Lam. (Malvaceae) , Sabal mexicana Mart. (Arecaceae) , Salix humboldtiana Willd. (Salicaceae) , Tabernaemontana alba Mill. (Apocynaceae) , and Trichilia havanensis Jacq. (Meliaceae) . The dominant species of the shrub stratum (2–5 m) of these forests are Acacia cornigera ( L.) Willd. ( Fabaceae ), and Pluchea odorata ( L.) Cass. ( Asteraceae ). Various species of lianas and vines also occur, including Agdestis clematidea Moc. & Sessé ex DC. (Phytolaccaceae) , Callicarpa acuminata Kunth (Lamiaceae) , Melothria pendula L. ( Cucurbitaceae ), Pisonia aculeata L. ( Nyctaginaceae ), Serjania triquetra Radlk. (Sapindaceae) , and Tetracera volubilis L. ( Dilleniaceae ). Heliconia latispatha Benth. (Heliconiaceae) and Syngonium podophyllum Schott (Araceae) predominate in the herbaceous stratum.

Etymology:— The name assigned to the new species refers to the State of Veracruz, where the type specimen was collected.

Phenology:— Forestiera veracruzana blooms between January and February, and bears fruit from February to May.

Additional specimens examined:— MEXICO. Veracruz: Mpio. Actopan, Caño Gallego, 3 km al N de Paso del Cedro , 25 May 1985, R . Acosta P . & N . Acosta B . 394 ( MEXU, XAL); Mpio. Actopan, Caño Gallego, 2 km de Paso del Cedro , 27 April 1985, R . Acosta P . 544 ( MEXU, XAL); Mpio. Tlacotalpan, 2 km al W de Pérez y Jiménez, 8 km al SW de Tlacotalpan , 1 February 1984, M . Nee & K . Taylor 29180 ( F, XAL); Mpio. Veracruz, 3 km by air SW of Santa Fe, junction of road to Tenenexpan and old free Hwy 140 from Veracruz to Xalapa, 23 February 1984, M . Nee & K . Taylor 29666 ( F, MO, NY, XAL); Mpio. Actopan, Caño Gallego, entrando por desvío de terracería, unos 3 km después de Paso del Cedro , 19 January 2021; 2, 10 and 23 February 2021, O . Palacios-Wassenaar, G . Castillo-Campos & I . Acosta R . 965, 969, 970, 971, 972, 973, 974, 978, 980 ( XAL); Mpio. Tlaltetela, Monte Rey , ejido Coetzala, 6 March 1983, L . Robles H . 68 ( XAL); Mpio. Puente Nacional, Tamarindo , 16 April 1973, F . Ventura A . 8179 ( ENCB, MEXU, XAL); Mpio. Apazapan, Los Baños Termales , 12 April 1978, F . Ventura A . 15188 ( ENCB, XAL); Mpio. La Antigua, 1 km de La Pureza , 26 March 1987, P . Zamora C . 321 (XAL). Tabasco: Mpio. Cárdenas, 2ª sección de Arroyo Hondo, 19 March 1983, F . Ventura A . 20057 (ENCB, XAL).

Notes: — Forestiera veracruzana grows in locations with conditions similar to those where F. corollata , F. isabeliae and F. rhamnifolia , occur. Specimens of the newly described taxon have frequently been misidentified as F. rhamnifolia and even as Neea psychotrioides . More recently, some specimens were identified as F. corollata when this new species was described by Cornejo & Wallander (2007). The authors of F. corollata pointed out that F. rhamnifolia is likely restricted to the region where it was first described ( Cuba). On the other hand, the authors of F. isabeliae reported this species as endemic to Costa Rica ( Hammel & Cornejo 2009).

Conservation status: — Forestiera veracruzana is usually found in remnants of riparian forests in heavily disturbed areas, surrounded by sugar cane plantations where they are continually threatened by deforestation and fragmentation for agricultural and livestock activities expansion. Riparian forests are one of the vegetation types with the smallest area in Mexico, less than 30,000 ha. In the state of Veracruz, more than 77% of the state’s surface has been transformed to agricultural and livestock activities, while in Tabasco, the estimated surface use change is 64% ( SEMARNAT 2016). Given the restricted distribution, low abundance, and potential threats to the habitat of this species, it is crucial to conserve and protect its remaining habitats, as well as promoting its inclusion as a species subject to special protection in the Official Mexican Standard for species at risk (NOM-59- SEMARNAT 2010) ( SEMARNAT 2010) and the Red List of threatened species of the International Union for Conservation of Nature ( IUCN 2017). Based on the facts mentioned above and our field experiences, there is a suspected population size reduction of ≥50% over the last 10 years caused by factors that have not stopped and whose effects are practically irreversible (IUCN criteria A2), and the quality of the habitat (section c) is strongly reduced by human activities in the eight localities where the species has been collected. Therefore, according to the IUCN Red List Categories and Criteria ( IUCN 2012), the species should be assessed as Endangered (EN A2c).

Figures

FIGURE 2. Illustration of Forestiera veracruzana Cast.-Campos & Pal.-Wass. sp. nov.: a, tree; b, branch with pistillate inflorescences; c, pistillate inflorescence; d, detail of pistillate flower; e, style types; f, staminate inflorescence; g, detail of stamen. Illustration by Rosa Pérez based on the type specimen O. Palacios-Wassenaar et al. 965 and 969 (XAL).