Louteridium tamaulipense A. Richardson

Daniel, Thomas F. & Tripp, Erin A., 2018, Louteridium (Acanthaceae: Acanthoideae: Ruellieae: Trichantherinae): Taxonomy, Phylogeny, Reproductive Biology, and Conservation, Proceedings of the California Academy of Sciences 65 (2), pp. 41-106 : 100-101

11. Louteridium tamaulipense A. Richardson , Sida 3: 448. 1969. TYPE.— MEXICO. Tamaulipas: ca. 5 km NW of Gómez Farias toward Aguacates [ca. 23°03’47.94”N, 099°10’08.06”W], 370 m, rocky slope in wet forest, 30-VI-1969 (flr), A. Richardson 1388 (holotype: TEX!, mounted on 4 sheets; isotypes: ENCB-image seen, F!, GH, K!, MEXU!, MICH!, NY!, OS-image seen, UC!, US!, WIS-images seen).

Perennial herbs to shrubs to 2.5 m tall, possibly epipetric ( Richardson 1972:63). Older (woody) stems prostrate (fide Richardson 1972:70), subquadrate or becoming irregularly fissured, lacking trichomes; younger (herbaceous) stems quadrate-sulcate to quadrate-alate, glabrous. Leaves apparently not all seasonally deciduous, ± evenly dispersed along young stems, petiolate, petioles to 85 mm long, blades subsucculent, ovate to elliptic, 80–260 mm long, 22–115 mm wide, 1.9–4 × longer than wide, acuminate to subfalcate to caudate at apex, subattenuate to attenuate at base, surfaces glabrous, margin entire to subsinuate-crenate. Inflorescence a terminal pedunculate thyrse to 250 mm long (including peduncle and excluding corollas), peduncles to 84 mm long, evenly pubescent with erect to flexuose glandular trichomes 0.1– 0.3 mm long, rachises similarly pubescent; dichasia sometimes modified by sympodial expansion and appearing as lateral branches (especially from proximal nodes of inflorescence), opposite, pedunculate, mostly 3–many-flowered, up to 115 mm long (excluding corollas), dichasial peduncles 3–45 mm long, pubescent like rachis. Bracts caducous, linear-lanceolate, 9–19 mm long, 1–2. 3 mm wide, abaxially pubescent like rachis. Bracteoles and secondary bracteoles caducous, lanceolate to linear-lanceolate, 9–14 mm long, 2–3 mm wide, abaxially pubescent like rachis. Flowers pedicellate, pedicels to 46 mm long, pubescent like rachis. Calyx 32–47 mm long, lobes subheteromorphic, membranaceous in texture (i.e., neither succulent nor coriaceous), apically acuminate, abaxially pubescent like rachis, posterior lobe planar, lance-ovate to ovate, 33–45 mm long, 10–17 mm wide, slightly to conspicuously larger than other lobes, lateral lobes lance-ovate to ovate, 29–39 mm long, 8–14. 5 mm wide. Corolla whitish to greenish yellow, 55–60 mm long, externally puberulent with scattered glands to 0.1 mm long, tube ca. 25–30 mm long, narrow proximal portion 3–6 mm long, 3–9 mm in diameter, throat 20–25 mm long, 20–30 mm diameter at mouth, lobes spreading to recurved, triangular to ovate, 15–27 mm long, 5. 2–9 mm wide, tapered and ± acute at apex. Stamens 2, 50–63 mm long, filaments glabrous distally (not seen proximally), thecae 11–15 mm long; staminodes (if present) not seen. Style 48–73 mm long, glabrous distally, pubescent with glandular trichomes proximally, stigma unequally 2-lobed, lobes often recoiled, ± oblong, 1.5– 3.5 mm long, width not determined. Capsule 22–28 mm long, diameter not determined, pubescent with glandular trichomes 0.05– 0.2 mm long, stipe 1–4 mm long. Seeds up to 20 per capsule, 3.5– 5 mm long, 3–4 mm wide, surfaces smooth or with low subconic tubercles.

PHENOLOGY.— Flowering: March–June, September, December; fruiting: March–April, September. Dressler (s.n.) notes that flowers are nocturnal. Richardson (1972) observed flowers of L. tamaulipense over 14 hours (from 18:00 to 08:00) in September of 1969. He noted: 1) that corollas began opening at sunset and falling in the early morning; 2) the lack of a floral scent; 3) that no nectar was found in the gibbous throat of corollas; 4) the nectary had an intensely sweet taste; and 5) hummingbirds visited flowers at dusk and in the early morning.

DISTRIBUTION AND HABITAT.— Northeastern Mexico (Tamaulipas; Fig. 8 ); plants occur on rocky limestone slopes in “tropical semi-evergreen and evergreen forest” ( Richardson 1972) at elevations from 340 to 560 (to 1400) meters. The vegetation at collection sites has been characterized on specimen labels as wet forest, cloud forest, and “selva mediana subperennifolia.”

CONSERVATION.— Louteridium tamaulipense is a local endemic that is known in the vicinity of the Sierra de Guatemala (= Sierra de Cucharas) in the northern Sierra Madre Oriental of Tamaulipas, where its known distribution (EOO = 43 km 2) is confined to the Reserva de la Biosfera El Cielo. Valiente B. et al. 285 noted that the species was locally very abundant. Several threats have been noted for the biosphere reserve, including: unplanned agricultural and forestry exploitation still being undertaken, overgrazing by livestock, increases in population density in surrounding buffer zones, poorly regulated eco-tourism, and poaching ( Anonymous 2007). Most (or all?) of the collections have been made in the buffer zones outside of the two core areas (in which most human travel and exploitation are prohibited) of the reserve. The buffer zones, including the EOO, include roads, villages, and tourist facilities. However, historical landsat images (2005 to 2016) via Google Earth Pro (2018) reveal relatively little change in vegetation cover in the EOO. Thus, based on current knowledge of the species, it is not known to qualify for a threatened category in spite of its very small EOO. Based on the information summarized above, the species is provisionally assessed as Near Threatened (NT).

DISCUSSION.— Richardson’s (1972) observations on floral phenology and visitation are very similar to those noted above for L. dendropilosum in Oaxaca. Louteridium tamaulipense shows some similarities to L. costaricense , and can be distinguished from that species of southern Central America by characters in the following couplet:

1a. Corolla externally pubescent with glandular trichomes 0.1– 0.5 mm long and eglandular trichomes 0.1– 1 mm long, lower lip 13–22 mm long; capsule 27–35 mm long, glabrous, stipe 7–12 mm long; inflorescence peduncles, rachis, peduncles of dichasia, and abaxial surface of bracts and bracteoles glabrous (or the bracts and bracteoles sometimes glandular-punctate but lacking elongate trichomes); bracts and bracteoles persistent................ L. costaricense

1b. Corolla externally puberulent with glands to 0.1 mm long, lower lip 27–31 mm long; capsule 22–25 mm long, pubescent with glandular trichomes 0.05– 0.2 mm long, stipe 1–4 mm long; inflorescence peduncles, rachis, peduncles of dichasia, and abaxial surface of bracts and bracteoles pubescent with glandular trichomes 0.1– 0.3 mm long; bracts and bracteoles caducous.................................................................. L. tamaulipense

ADDITIONAL SPECIMENS EXAMINED.— MEXICO. Tamaulipas: Mpio. Gómez Farías, 1 km SW de la Estación Canindo (sitio Cedros II), [ca. 23°02’23.25”N, 099°13’59.36”W], L . Hernández 3022 ( BRIT, QMEX); 8 km por la brecha W de Gómez Farías [ca. 23°02’43.51”N, 099°10’09.65”W], E . Martínez S . et al. 3854 ( ENCB, MEXU); ca. 5 km NW of Gómez Farías , A . Richardson 1398 ( K); Mpio. Gómez Farías , 1.5 km E de Gómez Farías, laderas de orientación WSW sobre la Sierra Chiquita [ca. 23°02’48.23”N, 099°08’26.35”W], A . Valiente B . 490 ( MEXU); Mpio Gómez Farías , 2 km W de Gómez Farías, postrimerias de la Sierra Madre Oriental, A . Valiente B . et al. 285 ( ARIZ, MEXU, RSA) ; Mpio. Gómez Farías , 1.5 km E de Gómez Farías, ladera de orientación W sobre la “Sierra Chiquita,” A. Valiente B . et al. 443 ( MEXU). Cultivated: University of California Botanical Garden (acc. no. 60.889-1), grown from plants collected by R . Dressler (s.n.) in Tamaulipas, above Encino, on road to lumber camp Julillo [ca. 23°07’37.45”N, 099°09’45.46”W], P . Hutchison 60-889-1 ( UC) .

Figures

FIGURE 8. Map of Mexico (showing states) and northern Central America with distributions of species of Louteridium endemic to Mexico: L. brevicalyx, L. dendropilosum, L. koelzii, L. parayi, L. rzedowskianum, and L. tamaulipense. Sym- bols may pertain to multiple collections.