Antiphytum brevicalyx N. Mend.

Mendoza-D´, Nidia, Ochoterena, Helga, Moore, Michael J. & Flores-Olvera, Hilda, 2020, Molecular and Morphological Evidence Reveals a New Species of Antiphytum (Echiochiloideae, Boraginaceae) from Guerrero, Mexico, Systematic Botany (Basel, Switzerland) 45 (1), pp. 190-199 : 191-197

Antiphytum brevicalyx N. Mend. , Flores Olv. & H. Ochoterena, sp. nov. TYPE: MEXICO. Guerrero: Municipio Eduardo Neri, 9 km (on the road to Filo de Caballos) west of Xochipala, 1635 m, 17° 46 0 41.40N, 99° 46 0 41.40W, 18 November 2016, N. Mendoza-D´ ıaz 643 with H. Flores Olvera, H. Ochoterena, A. Torres-Montúfar & C. Mart´ ınez-Rojas (Holotype: MEXU! Isotypes: ENCB!, FCME!, K!, MEXU!, MO!).

Antiphytum brevicalyx is the only species in the genus with the calyx shorter than the corolla tube at anthesis. It is similar to A. floribundum (Torr.) A.Gray in the inflorescence arrangement, but differs by the absence of a basal rosette (vs. present in A. floribundum ) and the presence of appendages on the corolla throat (vs. absent in A. floribundum ). Compared to A. peninsulare , the eremocarp of A. brevicalyx shares a medial position of the cicatrix as well as tuberculate and papillate ornamentation, but differs in shape (ovate in A. brevicalyx vs. triangular in A. peninsulare ).

Suffruticose perennial, erect, up to 1.20 m tall, covered by strigose and hispid indumenta, each trichome with several mineralized foot cells (lithocystic structure), with ambercolored and non-persistent glandular-capitate trichomes mainly on the younger parts of branches, leaves, bracts, bracteoles, and calyx. Stems numerous and broadly branched, arising from a main stem, branches alternate or opposite, nonfistulose (solid), slender (ca. 2.0 mm diam), with the most external layer exfoliating. Leaves basal, pseudobasal and cauline, sessile, blades linear-oblanceolate to oblanceolate, and lanceolate to narrowly elliptical-acuminate, margins flat or slightly thickened, entire, apices acute, nearly mucronate, bases truncate and non-connate, glandular trichomes only on the margins at the very base, surfaces concolorous, midvein visible as a groove in the adaxial face and as raised-strigose on the abaxial, secondary veins often not visible; basal leaves marcescent, not forming a rosette, up to 70.0(–80.0) 3 10.0(–15.0) mm; cauline leaves mostly alternate and only opposite at the base of the stem or the branches, 40.0–50.0(–60.0) 3 2.0–4.0(–5.0) mm, gradually smaller upward along the stem; pseudobasal leaves at the beginning of each branch, the newest ones 10.0 3 2.0 mm. Inflorescence ending in a flower (monotelic) with alternate paraclades, forming a terminal heterocladic determinate thyrse (thyrsoid) with dichasial branching, one side ending in a scorpioid cyme and the other side branching up to several times, first internode of a lateral axis (hypopodium) 40.0–60.0(–70.0) mm in length; mature scorpioid cymes up to 90 mm in length, loosely many-flowered, bracteate; floral bracts obovate (2:1) to oblong, sessile, mucronate, indumenta and midvein as on the leaves, blades 7.0–11.0 3 3.2–4.0 mm, gradually smaller upward along the cyme. Flowers perfect, sessile or subsessile (pedicel 0.2–0.5 mm in length); calyx strigose, glandular-capitate and scattered hispid trichomes on abaxial surface, accrescent in fruit, divided almost to the base, lobes asymmetric, mucronate to acuminate, scarious at the very base, two of them lanceolate and three obovate, ca. 2.0–2.2 3 0.3–0.4 mm, the bigger one obovate and resembling a floral bract, 2.5 3 1.0 mm, all shorter than the corolla tube at anthesis, up to 4.3 mm in length in fruit; corolla hypocrateriform (rotate), white, with five yellow papillose faucal appendages on the throat opposite to the corolla lobes, tube widely surpassing the calyx, 2.1–3.3 mm in length, 1.3 mm diam at the base, limb (4.0–) 4.25–5.25 mm diam, lobes oriented nearly perpendicular to the tube, imbricate, rounded, sinuate at apex, ca. (1.0–) 1.2–1.4 3 (1.0–) 1.2–1.4 mm, abaxially strigose at the middle; stamens inserted, alternate to the corolla lobes, adnate at ca. 1.7 mm from the base of the corolla tube; filaments up to 0.5 mm in length, slender; anthers oblong, slightly lanceolate, dorsifixed, ca. 0.8–0.9 3 0.2–0.3 mm; ovary with four ovules, style gynobasic, 0.7–0.8 mm in length at anthesis, stigma bilobed at the apex of the style (terminal). Fruit dry, covered by a persistent calyx, usually with 2–3 mature eremocarps; eremocarps lustrous, ovate and apically acuminate in ventral view, 1.8–1.9 3 1.3 mm, dorsally convex, tuberculate and papillate except at the apex of the tubercles; cicatrix at medial position on the ventral face, ovate, ca. 0.65 mm in length; one ventral keel (apical) straight from the apex of the eremocarp to the cicatrix apex not forming a stipe, without lateral (basal) keels; gynobase deltate-pyramidal, with four areoles corresponding to the cicatrix of each eremocarp, style plus stigmas 1.7(–2.0) mm, surpassing the eremocarps. Figures 2 , 3 .

Etymology —The specific epithet refers to the main morphological character that distinguishes A. brevicalyx from other Antiphytum ; it is the only taxon known in the genus in which the calyx is shorter than the corolla tube at anthesis ( Figs. 1C , 2C–D , 3F–G ).

Phenology —Flowering and fruiting from May to November.

Distribution and Habitat — Antiphytum brevicalyx is only known from the central region of Guerrero, in the municipios of Eduardo Neri and Tixtla de Guerrero ( Fig. 4 ). It occurs at

elevations ranging from 1080 to 1900 m, on limestone soils and probably also on gypsum, in deciduous forest with Brahea , Bursera , Juniperus , and Quercus .

Conservation Status — Antiphytum brevicalyx is known only from seven subpopulations in the state of Guerrero, Mexico ( Fig. 4 ). As a whole, the extent of occurrence is less than 261 km 2 and some subpopulations occur among areas of rainy season agriculture ( Fig. 4 ). Hence, habitat loss is the principal threat for the subpopulations. According to the IUCN (2012), this species meets the criteria B1ab(iii) for the category of Vulnerable (VU).

Paratypes — Mexico. — GUERRERO: Municipio Eduardo Neri, 9 km (on the road to Filo de Caballos) west of Xochipala , 1635 m, 17° 46 0 41.40N, 99° 46 0 41.40W, 18 November 2016, Mendoza-D´ ıaz et al. 644 ( MEXU!, FCME!, ENCB!, K!) ; La Yesera , 12.3 km N de Zumpango del R´ıo, 1420 m, 17°42 0 230N, 99° 30 0 040W, 25 October 1994, Jiménez-Ram´ ırez & Luna-Flores 971 ( FCME!) ; cerca de carretera, desv. a Xochipala , 1080 m, [17° 47 0 27.70N, 99°37 0 080W, 6 2 km], 26 October 1990, Peralta & Villegas 127 ( FCME!) ; 14 km SW de Xochipala, carretera a Filo de Caballos , 1900 m, [17° 45 0 52.60N, 99° 42 0 17.20W, 6 2 km], 17 October 1983, Soto-Nú~ nez 5626 ( MEXU!) ; along the road to Filo de Caballo, just above Xochipala at km 22, below La Laguna , 1600 m, 17°48 0 N, 99°36 0 W, 21 May 1987, Miller & Goreti 2826 ( MEXU!, MO!) ; 7 km O Carrizalillo, 1600 m, 17°51 0 340N, 99°40 0 170W, 09 September 1993, Mart´ ınez-Gordillo 798 ( FCME!, MEXU!). Municipio Tixtla de Guerrero, Summit of mountains northeast of Chilpancingo on road to Chilapa , 6000 ft, [17°34 0 140N, 99° 26 0 25.10W, 6 2 km], 19 August 1948, Moore Jr. & Wood, Jr. 4672 ( GH!) .

Additional Specimens Examined for the Morphological Study— Antiphytum caespitosum . Mexico. — GUERRERO: Municipio Tlapa, on El Salado bridge, 8 km N of Tlapa,road to Huamuxtitlan, 990 m, 16 November 1982, Mart´ ınez et al.2680 (MEXU!). Antiphytum heliotropioides . Mexico. — NUEVO LEÓN : Municipio Rayones, road Galeana-Rayones, 6 km N of Los Nogales and 17 km N of Galeana, 1360 m, 24° 55 0 43.70N, 100° 03 0 51.10W, 24 September 2016, Mendoza- D´ ıaz et al. 629 (MEXU!). Antiphytum peninsulare . Mexico. — BAJA CALIFORNIA SUR: Gulf of California, volcanic hillside near north west end of Isla San Marcos, 27°15 0 N, 112°07 0 W, 28 March 1962, Wiggins 17328 (MEXU!).

Figures

FIG. 2. Antiphytum brevicalyx. A. General appearance of a young plant showing detail of the abaxial surface of a basal leaf (from Mendoza-D´ıaz et al. 644C). B. General appearance of an older individual showing detail of the adaxial surface of the cauline leaves (from Mendoza-D´ıaz et al. 643A). C. Portion of cyme inflorescence (from Mendoza-D´ıaz et al. 644A). D. Flower (from Mendoza-D´ıaz et al. 644A). E. Open corolla (from Mendoza-D´ıaz et al. 644A). F. Fruit with three eremocarps removed showing the attachment point at the gynobase (from Mendoza-D´ıaz et al. 643A). G. Eremocarp in ventral and lateral view (from Mendoza-D´ıaz et al. 643A).

FIG. 3. Antiphytum brevicalyx in the field (Mendoza-D´ıaz et al. 643, 644). A. Young individual with flowers and associated vegetation. B. Mature individual. C. Basal leaves in a young individual. D. Individual showing the habitat and soil. E. Thyrsoid view from above. F. Partial inflorescence. G. Portion of inflorescence. H. Flower at anthesis showing the faucal appendages. Photos by Helga Ochoterena.

FIG. 1. Combined parsimony tree (L 5 172) using ITS and ndhF-rpl32 sequences, including microstructural DNA characters. A. Single most parsimonious tree highlighting Antiphytum brevicalyx. Sequences in gray are identical to the sequence of the first black-colored accession name above. Numbers above branches correspond to jackknife support above 64%. Solid boxes on branches indicate synapomorphic changes, open boxes indicate homoplasy, and colored boxes correspond to microstructural characters, as follows: blue boxes represent gap characters, and pink boxes represent simple sequence repeats (SSRs). Numbers next to the microstructural synapomorphies indicate their base pair position(s) in the aligned matrix of the respective locus. A schematic representation of the eremocarp cicatrix position is shown next to the hypothetical ancestor of each condition: SB 5 supra-basal; M 5 medial; IM 5 inframedial. B. Geographic origin of A. brevicalyx accessions from Guerrero, Mexico. Mapped collections that are not connected to the phylogeny lack sequences. C. Flowers of A. brevicalyx showing the characteristic calyx: shorter than the corolla tube. D. A. caespitosum, the other species distributed in Guerrero, showing the basal leaf rosette characteristic of the entire clade (dotted box).

FIG. 4. Distribution map of A. brevicalyx within Guerrero, showing the two municipios (Eduardo Neri and Tixtla de Guerrero) in which the species has been recorded, and vegetation types. The inset map shows the locations of the two municipios within Guererro and the location of Guerrero in Mexico.