A new species of Amphitecna (Bignoniaceae) endemic to Chiapas, Mexico

Abstract Amphitecna loreae Ortiz-Rodr. & Burelo, sp. nov. (Bignoniaceae), a new species endemic to the karst rainforest in southern Mexico, is described and illustrated. The new species differs from the other species of Amphitecna by the combination of cauliflorous inflorescences, larger flowers, buds rounded at apex, and globose-ellipsoid rather than acuminate fruits. A key to the Mexican species of Amphitecna is presented.


Introduction
Bignoniaceae (calabash tree family) includes about 82 genera and approximately 900 species of trees, shrubs and woody vines distributed mainly in tropical areas around the world (Lohmann and Ulloa 2006). Th e most recent tribal classifi cation of Bignoniaceae (Fischer et al. 2004), recognizes seven tribes: Bignonieae, Coleeae, Crescentieae, Eccremocarpeae, Oroxyleae, Tecomeae, and Tourrettieae. However, phylogenetic analysis based on molecular characters (Olmstead et al. 2009) shows that many of the above tribes, as traditionally had been recognized, do not represent monophyletic groups. Based on this phylogenetic hypothesis (Olmstead et al. 2009), the 82 genera of Bignoniaceae can be organized in the tribes Bignonieae, Catalpeae, Jacarandeae, Oroxyleae, Tecomeae, and Tourrettieae. In addition, a strongly supported clade informally named Crescentiina is recognized (Olmstead et al. 2009, Collevatti andDornelas 2016).
Th e Crescentiina clade contains approximately 34 genera and 300 species, and it is formed by two subclades corresponding to the Tabebuia alliance and the Paleotropical clade (a group of genera traditionally assigned to Tecomeae and Coleeae) (Olmstead et al. 2009). Th e Tabebuia alliance, is a lineage endemic to the Neotropics and consists of 14 genera and 147 species of trees and shrubs, from which stands a small clade of three genera traditionally assigned to the tribe Crescentieae, Amphitecna, Crecentia, and Parmentiera, which together comprise nearly 36 species of trees distributed in Central America, northern Colombia and the Greater Antilles (Gentry 1980, Grose andOlmstead 2007a).
Th e genus Amphitecna is easily diff erentiated from Crecentia and Parmentiera by the combination of simple, alternate leaves and the greenish fl owers with the lobes of the petals fused (Gentry 1980). Th e genus comprises about 20 species (Grose and Olmstead 2007b), most of them known to be restricted to a few localities. In Mexico, the genus Amphitecna is particularly diverse and consists of roughly 10 species, all of them having their southernmost distribution in Guatemala and Belize.
During the course of several botanical explorations in southern Mexico, a species of Amphitecna with a unique combination of features diff ering from all other members of the genus was collected in a karst forest of Chiapas. In this paper, this interesting species is described and illustrated and its affi nities with other species of Amphitecna are discussed. Furthermore a key to Mexican species of Amphitecna is presented.

Materials and methods
In order to confi rm the status of this new species we visited and reviewed the specimens of Amphitecna deposited in herbaria XAL, HEM and CHIP (Th iers 2016). Also, we consulted the digitized type specimens available at JSTOR Global Plants (http:// plants.jstor.org/). Th e putative new species was recognized using the unique combination of features criteria (Donoghue 1985) through comparisons with morphologically similar species and literature review (Gentry 1980). Finally, description of the species was elaborated following terminology presented in Hickey (1973).
We assessed the conservation status by calculating the extent of occurrence (EOO) and the area of occupancy (AOO) using the GeoCAT tool (Bachman et al. 2011) and applying the IUCN Red List Categories and criteria (IUCN 2001).
Additionally, coordinates of occurrence data were assembled for the new species herein described and for the morphologically similar species, which were obtained from the Global Biodiversity Information Facility (GBIF; http://www.gbif.org/spe-cies/4003073), supplemented with records from fi eld collection and with information available in the herbarium specimens. Th en climate layers were obtained at a 30 arc-sec (c. 1 km2) resolution from the WorldClim database (Hijmans et al. 2005) and for all occurrence records, we extracted data from 19 climatic variables using ArcView v3.2 (ESRI, Redlands, CA, USA). Using these data, we performed a principal components analysis (PCA) using a correlation matrix with PAST ver. 3.06 (Hammer et al. 2001) to explore patterns of climatic diff erentiation between species.
Diagnosis. Amphitecna loreae is distinguishable from the other species of Amphitecna by a combination of its caulifl orous infl orescences, large fl owers, buds rounded at apex, and broadly elliptical to spherical rather than acuminate fruits. Amphitecna tuxtlensis, A. montana and A. latifolia, also distributed in Mexico, have affinities with A. loreae and share the caulifl orous infl orescences and leaves less than 50 cm long. However, A. tuxtlensis diff ers in having the fl ower buds pointed at the apex and fruits elliptic, acute to acuminate at apex, and A. montana diff ers in having larger leaves, long pedicellate fl owers and elliptical fruits shortly pointed at the tip, while A. latifolia diff ers in having obovate to widely elliptic leaves, rounded to mucronate at apex with poorly defi ned petioles ( Figure 1).
Description. Trees, 15-25 m and 15-50 cm DBH, the secondary branches terete. Leaves, alternate-verticillate, clustered near the apex of the branches, olive-green when dry, glabrous, 10-20 cm long, 2-5 cm wide, oblanceolate to narrowly elliptic, acuminate, subcoriaceous, acute to attenuate basis, midrib slightly raised on the upper surface, prominent on the lower surface; secondary veins 11-14 on a side, slightly raised above, prominent below; petiole short, to 2 cm long, merging with attenuate leaf base. Infl orescences, groups of two or three fl owers, with an unpleasant odor, which are borne on leafl ess portions of old branches and along the main trunk (caulifl ory). Flower buds, rounded at apex. Flowers pendant, pedicel 35-60 mm long; calyx campanulate, 28-38 mm long, more or less coriaceous, evenly 2 to 3-labiate to below the middle, circumscissile; corolla radially symmetric, pale green, tubular-infundibuliform, 48-60 mm long, 30-40 mm wide at the mouth of the tube, the basal part of the corolla a straight tube, 15-25 mm long, the lobes fused in to frilly-margined rim; stamens included, inserted 18-28 mm from base of the tube, the anther thecae divergent, 4-7 mm long, the fi laments 18-30 mm long; the staminode, when present, less than 20 mm long, inserted 10-20 mm from base of the tube, sometimes well developed (with one or two small thecae) to give the impression of being a fi fth stamen; ovary, up to 3 mm long and 2.5 mm wide, broadly elliptical, glandular-papillose; pistil 40-60 mm long with the stigma bifurcate; disc annular-pulvinate, about 6 mm in diameter; fl owers are often found with signs of herbivory, in which the ovule and disc are not present. Fruits broadly elliptical to spherical, 70-100 mm long, 60-80 mm wide.
Habitat and ecology. Th e species is only known from Chiapas, Mexico. It is a rare species at the type locality in the ecological reserve La Pera. Th e species inhabits the karst areas, mainly in the tropical rainforest. It is a canopy tree and coexists with species of Quercus lancifolia Schltdl. & Cham., Q. corrugata Hook., Calatola costaricensis Standl., Spathacanthus hahnianus Baill, and Quararibea funebris (La Llave) Vischer.
Phenology. Mature fl owers and fruits were collected in March and April; buds, ripe and immature fruits were observed in the same months.
Etymology. Th e specific epithet honors Francisco Lorea Hernández, in recognition of his many important contributions to our knowledge of the Mexican fl ora.
Conservation status. Currently we lack the necessary information to objectively defi ne the conservation status of Amphitecna loreae. However, according to the criteria

black dots) and
Amphitecna tuxtlensis (blue squares). In colours similar to those of the species the 95% confi dence ellipses produced by PCA analysis. established by the IUCN, it is possible to tentatively determine that the species is Critically Endangered [CR B1ab (iii)]. Although the only known population of the species is located within a protected natural area, A. loreae appears to be rare ecologically and only eight individuals in one hectare of sampling were recorded (Escobar-Castellanos 2016). Th e Area of occupancy (AOO) is 12,000 km² and the Extent of occurrence (EOO) is 0.763 km², suggesting a very restricted overall distribution. Furthermore, the tropical rain forest in this region of Chiapas is seriously fragmented and only small remnants persist.
Additional specimens examined. Mexico. Chiapas, Berriozabal: Rancho "El Retiro", atrás de el rancho "El Zapote". 13 km al N de Berriozábal camino a Joaquín Miguel Gutiérrez, 16°52'09. Th e four cauliferous species discussed in the diagnoses have diff erent distribution ranges with diff erent climatic preferences (Figure 2). Amphitecna tuxtlensis has two disjunct populations in Veracruz, one in the area of the Los Tuxtlas and another in the Uxpanapa-Chimalpas region, where it inhabits the tropical rainforest. Amphitecna montana is distributed along the Sierra Madre de Chiapas and inhabits the cloud forest above 1200 m. Amphitecna latifolia is distributed intermittently in areas near to the Atlantic coast of Mexico, where it inhabits mainly in riparian vegetation and mangrove associations. In contrast, A. loreae is endemic to Chiapas and it is known only from a single locality at the municipality of Berriozabal, Chiapas. Th e species grows on a karstic zone at approximately 900-1,150 m and it inhabits the tropical rainforest (Table 1).