Ternstroemia guerrerensis O. Alcántara-Ayala, I. Luna-Vega, F. S. Maradiaga-Ceceña & H. Alvarado-Sizzo, 2022

Alcántara-Ayala, Othón, Maradiaga-Ceceña, Francisco S., Luna-Vega, Isolda & Alvarado-Sizzo, Hernán, 2022, Ternstroemia guerrerensis (Pentaphylacaceae), a new endangered cloud forest tree from Guerrero, Mexico, Phytotaxa 561 (2), pp. 162-172 : 165-170

Ternstroemia guerrerensis O. Alcántara-Ayala, I. Luna-Vega, F. S. Maradiaga-Ceceña & H. Alvarado-Sizzo , sp. nov. ( Figs. 1 and 2 ).

Type:— MEXICO. Guerrero: Municipality of Ayutla de los Libres , Camino de Ayutla a Pascala del Oro , km 23.8 o camino de Horcasitas a Ayutla de los Libres pasando la desviación a Tres Cruces. 16°59’12.60”N 98°57’20.60”W, 1586 m asl, 3 July 2010, O. Alcántara-Ayala et al. 6793 (holotype FCME!: 177891; isotype FCME!: 177899) .

Ternstroemia guerrerensis resembles Ternstroemia lineata subsp. lineata in the shape and color of the flower. It differs from T. lineata subsp. lineata by its obovate leaves (versus spatulate), lateral nerves generally distinctly slightly impressed on the adaxial side (versus generally not visible), apex generally retuse (versus rounded), margin notoriously crenate or serrulate towards the apex (versus entire to sub-entire), petiole adaxially reddish in living state (versus whitish), pedicels adaxially reddish in living state (versus usually greenish), the two shorter outer sepals with the margin glandular dentate (versus entire, eglandular), slightly scarious, internal sepals margin entire, connective generally briefly extending, and number of ovules in locule 8 to 9 (versus 5 to 6).

Little tree, 2–5 m tall. External bark reddish-gray, glabrous. Twigs verticillate, cylindrical. Leaves spirally arranged and clustered toward the branch tips; petiole 4.1–5.4 mm long, 1.3–1.6 mm diameter, terete, adaxially slightly canaliculate, rounded abaxially, glabrous, adaxially reddish in living state; lamina 6.8–8.5(–10.8) × 2.8–3.7(–5.4) cm, obovate, glabrous; lateral nerves generally distinct, slightly impressed on the adaxial side; midrib adaxially canaliculate, conspicuously elevated and rounded abaxially; base attenuate; apex acute or obtuse, sometimes retuse; margin weakly revolute, notoriously crenate or serrulate to the apex. Flowers axillary, single, at the apex of the twigs, pedicels curved, terete, 1.6–2.0 cm long, 1.6–1.8 mm wide in the middle, adaxially reddish in living state. Bracteole opposite, subequal, one inserted immediately below the calyx and the other ca. 2.5 mm below calyx, deltate in fresh state, triangular in dry state, (2.2 –)2.5–3.0 × 1.2–2.0 mm, midrib prominent as a keel, margin glandular-denticulate and sometimes with simple hairs, apex acute, base truncate. Sepals 5, imbricate-quincuncial, glabrous on both surfaces, apex rounded; external sepals ca. 6.3–7 × 5.5–6.5 mm in flower after anthesis, widely ovate, margin glandular dentate, slightly scarious, apex rounded; internal sepals 7–8(–8.2) × 6.2–6.5 mm after anthesis, ovate, margin entire, apex rounded. Petals 5, white, imbricate, ca. 1.0–1.2 × 0.7–1.0 cm, orbicular, apex rounded, connate at the base. Stamens ca. 60, united at the base, adnate to the petals, filaments ca. 2.5 mm long, flat, anthers ca. 2.4 mm long, connective generally extending, 0.3–0.4 mm length. Ovary ca. 4 mm in bud, conical, glabrous, 2-locular, with 8–9 ovules per locule, placentation apical; style simple ca. 2 mm long, straight; stigma punctiform. Fruit green when immature, ochre when ripe, ovoid, 1.5 cm long × 0.85 cm in diameter, peduncle reddish on the adaxial side when immature to yellow-ochre when ripe, 0.9 to 1.2 cm length, calyx greenish-yellow, sepals generally adpressed to the fruit when immature, 0.8 cm long. Seeds 4.5–4.9 mm length, 1.8–2.5 mm diameter, covered by a red fleshy structure.

Phenology:—Flowering: May to July. Fruiting: August to November.

Paratypes:— MEXICO. Guerrero: Municipality of Ayutla de los Libres, Camino de Ayutla a Pascala del Oro , km 23.8 o camino de Horcasitas a Ayutla de los Libres pasando la desviación a Tres Cruces , 16°59’12.60”N, 98°57’20.60”W, 1586 m, 3 July 2010, O. Alcántara-Ayala et al. 6788 (FCME177892!); loc. cit., 1586 m, 3 July 2010, O. AlcántaraAyala et al. 6791 (FCME177893!); Municipality of Acatepec , Tres Cruces, 17°0’56.66”N, 98°55’37.90” W, 1420 m, 29 October 2021, O. Alcántara-Ayala & F.S. Maradiaga-Ceceña 7985 (FCME177897!), loc. cit., 1420 m, 29 October 2021, O. Alcántara-Ayala & F.S. Maradiaga-Ceceña 7986 (FCME177898!) .

Distribution and habitat:—This species inhabits disturbed fragments of tropical montane cloud forest (TMCF), with Magnolia vazquezii Cruz Durán & Vega (2008: 24) and Quercus spp. in the canopy, pine-oak forest.

Etymology: —The specific epithet refers to the state of Guerrero in Mexico, where this species was collected.

Conservation status: —This species was found during a visit to the type locality in 2010; only ten individuals were observed. Subsequent visits to the same locality showed the near loss of this population due to clearance. In 2021, we located a new population in nearby areas composed of fifteen individuals. In addition, a search in Mexican herbaria allowed us to find only two records of the same species in other localities close to the type locality. Therefore, we believe that it is an endemic species to this region. Considering that its natural habitat is highly altered, we treated it as a threatened species.

The study localities of Ternstroemia guerrerensis are unprotected, and the primary threats are livestock for seasonal grazing and agriculture. Therefore, after revising the distribution of populations and numbers of individuals of this new species, we conclude that T. guerrerensis must be included as A (Amenazada) in the NOM-059-SEMARNAT-2010 (SEMARNAT, 2010), and as Critically Endangered and in the UICN Red List as suggested when performing a geospatial analysis using the Geospatial Conservation Assessment Tool (GeoCat in http://geocat.kew.org/), that performs rapid geospatial analysis for Red List assessments (https://www.iucnredlist.org/). Cheek et al. (2019) suggested that all newly discovered species are likely to be threatened since widespread species have already been discovered.

Morphological characters:—The new species had traditionally been identified as Ternstroemia lineata subsp. lineata ; however, it differs in several morphological characters from this species and all other related species included in the T. lineata species complex ( Alcántara-Ayala et al. 2020). These morphological characteristics also differentiate it from Ternstoemia species that inhabit adjacent areas, such as T. sylvatica and T. tepezapote (Luna-Vega and AlcántaraAyala 2002) .

The new species is distinguished from other species by the leaf shape and apex, the peduncle length and color, the color of the petioles, the length of the connective extension of the anthers, and the number of ovules per locule ( Table 2 ).

Molecular phylogeny: —The most phylogenetically informative regions were the ITS1 (35 out of 350) and parsimony-informative sites (18) as well as in relative variation (10.0% variable sites). ITS2 was also informative, with 25 variable sites out of 266 (9.39% variable sites) and 12 parsimony-informative sites. Finally, the 5.8s was useless, showing only one variable site.

Our phylogeny is well-supported ( Figure 3 ). Within the American group, the three individual samples of Ternstroemia guerrerensis sp. nov. (GenBank accessions OM992283 , OM992284 , and OM992285 ) showed identical DNA sequences forming a well-supported clade (ML-Bootstrap= 96, Bayesian PP= 1), sister to the Ternstroemia lineata complex (TLC). These two groups, TLC and T. guerrerensis sp. nov. make a fully supported group (ML-Boostrap= 100, Bayesian PP= 1.0), distinguishable from Asian Ternstroemia . Even though our phylogeny lacks a thorough sampling of the genus Ternstroemia , our species sampling clearly shows T. guerrerensis sp. nov. as an independent lineage.

Figures

FIGURE 1. Ternstroemia guerrerensis sp. nov. A) branch with leaves and flowers; B) ovary with sepals; C) detail of corolla with the androecium adnate; D) stamen; E) detail of retuse apex; F) fruit with sepals, and G) seeds. Illustration by Ramiro Cruz Durán based on the type specimen O. Alcántara-Ayala et al. 6793 (FCME).

FIGURE 2.A-C, Ternstroemia guerrerensis; D-F, T. lineata subsp. lineata.A and D, twig leaf arrangement and leaf shape on both species; B and E, T. guerrerensis, and T. lineata subsp. lineata flowers; C and F, flower arrangement, length, and color of the pedicels in the two species.

FIGURE 3. The phylogenetic tree based on ML shows the position of Ternstroemia guerrerensis sp. nov. Bootstrap values are given at the left above branches. Posterior probabilities are given at the right above branches.