Louteridium purpusii Brandegee, Univ. Calif. Publ. Bot.

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 : 97-98

9. Louteridium purpusii Brandegee, Univ. Calif. Publ. Bot. 6:68. 1914. TYPE.— MEXICO. Chiapas: Finca Irlanda [ca. 15°10’24.94”N, 092°20’10.22”W], VIII-1913 (flr, frt), C. Purpus 6969 (holotype: UC!; isotypes: BM!, EAP-image seen, F!, GH!, MO!, NY!, US!, Z-image seen).

Shrubs or trees to 9 m tall, terrestrial. Older (woody) stems subquadrate-sulcate, ± scurfy and lenticellate, often puberulent like young stems; younger (herbaceous) stems quadrate to quadrate-sulcate and ± irregularly striate, glabrous or ± evenly puberulent with erect to retrorse to antrorse eglandular trichomes to 0.05 mm long. Leaves apparently not all seasonally deciduous, ± evenly distributed along young stems, petiolate, petioles to 40 mm long, blades membranaceous, ovate-elliptic to obovate-elliptic to obovate, 130–380 mm long, 40–115 mm wide, 2.1–4.3 × longer than wide, acuminate to acute-apiculate at apex, acute to attenuate at base, adaxial surface glabrous or puberulent like young stems, abaxial surface paler than abaxial surface, glabrous or pubescent with mostly antrorse eglandular trichomes 0.05– 0.1 mm long along major veins, margin often undulate, entire to sinuate to crenate to crenate-dentate. Inflorescence a terminal pedunculate raceme to racemose thyrse to 63 cm long (including peduncles and excluding corollas), peduncle to 20 cm long, glabrous or pubescent like young stems, rachis puberulent with (retrorse to) erect to flexuose to antrorse eglandular trichomes to 0.05 mm long; dichasia modified by very short expansion between pairs of succeeding flowers with the congested dichasial axis becoming a ± fan-shaped to multi- and tortuously-branched racemelike lateral short-shoot to 15 mm long, opposite (and alternate?), sessile to subsessile, 3–many-flowered, to 60 mm long (excluding corollas), dichasial peduncles (if present) to 2 mm long, pubescent like rachis. Bracts caducous, not seen. Bracteoles and secondary bracteoles caducous, lance-linear to linear-elliptic, 5–13 mm long, 1–2. 5 mm wide, abaxially pubescent like rachis. Flowers pedicellate, pedicels to 55 mm long, puberulent with erect to retrorse (to antrorse) eglandular trichomes to 0.05 mm long. Calyx 22–40 mm long, lobes distinct or fused at base up to 1 mm, heteromorphic, membranaceous, abaxially puberulent like pedicels and sometimes with a few sparse stipitate glands up to 0.2 mm long as well, also inconspicuously glandular-punctate, posterior lobe conduplicate, ovate to elliptic to obovate, 21–38 mm long, slightly shorter than to slightly longer than lateral lobes, 8. 5–15 mm wide, acuminate to falcate at apex, lateral lobes sublunate, 22–37 mm long, 6–9 mm wide, acute to subfalcate at apex. Corolla cream to yellow-greenish and tinged with maroon, 45–52 mm long, externally pubescent with stipitate glandular trichomes 0.05– 0.3 mm long (sometimes with flexuose eglandular trichomes to 0.2 mm long on or near margins of lobes as well), tube 25–33 mm long, narrow proximal portion 3–5 mm long, 7 mm in diameter near midpoint, throat 22–30 mm long, 25–35 mm diameter at mouth, lobes spreading to recurved, triangular to ovate, 12–21 mm long, 10–13 mm wide, rounded at apex. Stamens 2, 65–75 mm long, filaments glabrous distally, pubescent proximally with eglandular trichomes, thecae 10–12 mm long; staminodes (if present) not seen. Style 85–92 mm long, glabrous distally (not seen proximally), stigma equally 2-lobed, lobes elliptic, 1.4– 2 mm long, width not determined. Capsule 22–30 mm long, 5–7. 5 mm in diameter, densely pubescent with stipitate glandular trichomes (0.05–) 0.1– 0.4 mm long, stipe 3– 3.5 mm long. Seeds up to 12 per capsule, 4.5– 5.2 mm long, 4.5– 5 mm wide, surfaces smooth.

PHENOLOGY.— Flowering and fruiting: August–March.

DISTRIBUTION AND HABITAT.— Southern Mexico (Chiapas), Guatemala ( Fig. 10 ); plants occur in wooded ravines in montane rain forests on the Pacific versant at elevations from 600 to 2000 m.

ILLUSTRATION.— Figure 4F.

LOCAL NAME.— “palo de agua,” (Quarles van Ufford 137).

CONSERVATION.— Louteridium purpusii has an EOO of 944 km 2. Two prominent threats are evident throughout most or all of its known distribution, coffee agriculture and volcanic eruptions. Numerous active volcanos lie within and adjacent to the entire EOO of this species. Most of the occurrences of the species are within the prime growing elevations (i.e., 900 to 1800 m) for Coffea arabica L., and within two important coffee-growing regions (the Soconusco region of Chiapas, Mexico and the departments of San Marcos and Quetzaltenango in Guatemala). Mexico and Guatemala are two of the top 10 coffee-producing countries in the world ( Anonymous 2003, 2018). Increasing demand for coffee worldwide (e.g., Lorenzetti 2016) has or could result in increased conversion of natural vegetation in the EOO of this species to agriculture. Thus, coffee production would appear to be the more immediate threat to L. purpusii . However, based on either threat, there would appear to be a single location for the species. A preliminary conservation assessment of Endangered (EN; B1, a, b; IUCN 2017) is proposed for this species.

DISCUSSION.— This species resembles some plants of L. mexicanum (see discussion under that species), but differs by its more obovate leaves and pubescence. Additional morphological tendencies that distinguish these species include the more racemose (vs. thyrsoid) inflorescences of L. purpusii (with dichasial peduncle lengths of 0 to 2 (vs. 1 to 22) mm; the caducous bracteoles (vs. usually persistent in L. mexicanum ); and the generally longer styles (85 to 92 vs. 72 to 85 mm long), capsules (22 to 30 vs. 16 to 24 mm long), and capsular stipes (3 to 3.5 vs. 1 to 2 mm long). The distributional ranges of these two species are not known to overlap and are restricted to different versants of Mexico and Guatemala.

ADDITIONAL SPECIMENS EXAMINED.— MEXICO. Chiapas: Mpio. Unión Juárez, 17 km E of Cacahoatán [ca. 15°1’56.19”N, 092°5’27.65”W], D. Breedlove & A . Smith 31613 ( DS, MEXU, MO); Finca Nubes [ca. 15°03’43.30”N, 092°08’39.20”W], F . Miranda 1723 ( LL, US); from [Finca San Antonio] Chicharras , E . Nelson 3749 ( US); Finca San Antonio [Chicharras; ca. 15°7’26.12”N, 092°14’45.30”W], L . Quarles van Ufford 137 ( U) . GUATEMALA. Quezaltenango: Sta. María Ikibál [not located, possibly Santa María de Jesús], C . Bernoulli & O . Cario 2254 ( K); lower S slope of Volcán Santa María , 0.3 mi W of jct. Finca Pirineos road with hwy. 95 at KM 97 [ca. 14°41’5.41”N, 091°32’50.04”W], C . Broome 728 ( CAS, DUKE, F, MICH, US); de la represa de Santa María al Volcán Pecul [ca. 14°43’26.73”N, 091°30’42.09”W], Equipo CECON 1063 ( MO); San José Buena Vista, Costa Cuca, [ca. 14°41’53.74”N, 091°46’35.82”W], L . Rodríguez 444 ( P); Palmar, [ca. 14°39’12.22”N, 091°35’25.38”W], A . Skutch 1451 ( F, US); Finca Pireneos, below María de Jesús , [ca. 14°41’38.02”N, 091°32’30.77”W], P . Standley 68259 ( F, US); along old road between Finca Pirineos and Patzulín, P . Standley 86714 ( F); 86726 ( F), 86749 ( F), 86750 ( F, US), 86763 ( F); along Quebrada San Gerónimo, Finca Pirineos , lower S-facing slopes of Volcán Santa María, between Santa María de Jesús and Calahuaché, J . Steyermark 33435 ( F); off Hwy. 95 at KM 197 , old road to Finca Pirineos , ca. 0.5 mi from main hwy., D. Stone 3086 ( DUKE); Colomba, Finca San Francisco Pie de la Cuesta, 14°43’41.05”N, 091°43’04.45”W, L . Velásquez & W. López 1792 ( CAS). San Marcos: Finca El Porvenir along Río Chopal, S-facing slopes of Volcán Tajumulco [ca. 14°57’36.58”N, 091°56’40.73”W], J . Steyermark 37501 ( F); El Tumbador, finca Nueva Granada, 14°51’19.9”N, 091°53’05.9”W, L . Velásquez et al. 658 (BIGU, CAS).

Figures

FIGURE 10. Map of southern Mexico (showing states) and northern Central America with distributions of Louteridium chartaceum, L. donnell-smithii, and L. purpusii. Symbols may pertain to multiple collections.