Louteridium chartaceum Leonard, Publ. Carnegie Inst. Wash.

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 : 72-75

2. Louteridium chartaceum Leonard, Publ. Carnegie Inst. Wash. 461:197. 1936. TYPE.— BELIZE. Belize: Gracie Rock, Sibun River [ca. 17°23’13.67”N, 088°27’1.91”W], 24-III-1935 (flr, frt), P. Gentle 1526 (holotype: US-1589669!; isotypes: A-image seen, ARIZ!, K!, LL!, MICH!, MO!, NY!, US-1589668!, WIS-image seen).

Shrubs to trees to 3.5 m tall, often epipetric. Older (woody) stems irregularly striate, ± lenticellate, lacking trichomes; younger (herbaceous) stems subterete to subquadrate, glabrous. Leaves seasonally deciduous, ± clustered just proximal to inflorescence, petiolate (or distal leaves subsessile), petioles to 70 mm long, blades subsucculent, ovate to elliptic (to obovate-elliptic), 70–285 mm long, 30–95 mm wide, 1.7–3.7 × longer than wide, acuminate to subfalcate at apex, rounded to acute (distal leaves) to attenuate (proximal leaves) at base, surfaces glabrous, margin entire and sometimes with inconspicuous marginal swellings/encrustations. Inflorescence a terminal (raceme to) racemose thyrse to thyrse to 580 mm long (including peduncle and excluding corollas), peduncle to 240 mm long, glabrous, rachis glabrous; dichasia expanded or sometimes modified by very short expansion between pairs of succeeding flowers with the congested dichasial axis becoming a ± linear racemelike lateral short-shoot to 10 mm long, opposite, sessile to pedunculate, (1–) many-flowered, to 70 mm long (excluding corollas), dichasial peduncles (if present) to 24 mm long, glabrous. Bracts caducous, subfoliose, ovate to lanceolate, 18–52 mm long, 3. 5–18 mm wide, reduced in size toward apex, abaxially glabrous. Bracteoles caducous, triangular, 2–7 mm long, 1.5– 2.5 mm wide, abaxially glabrous. Flowers pedicellate, pedicels 30–43 mm long, glabrous. Calyx 18–26 (– 29 in fruit) mm long, lobes fused at base for 1– 1.5 mm, subheteromorphic, subsucculent, linear to lance-linear, 15–25 mm long, 3–5 mm wide, (subrounded) to acute at apex, abaxially glandular-punctate (punctations to 0.1 mm in diameter, sometimes sparse) but lacking elongate trichomes, posterior lobe subplanar to subconduplicate, 15–23 mm long, equal to or short- er than lateral lobes, 3–5 mm wide, lateral lobes 17–25 mm long, 3. 2–5 mm wide, all lobes (subrounded to) acute at apex. Corolla light green or greenish yellow with lobes usually becoming slightly maroon-tinged and darker maroon at distal tips with age, 35–40 mm long, externally glabrous, tube 21–23 mm long, narrow proximal portion 5–8 mm long, 6–11 mm in diameter near midpoint, throat 14–17 mm long, 19–23 mm in diameter at mouth, lobes recurved to recoiled, oblong to ovate-elliptic, 12–14. 5 mm long, 8.5–10. 5 mm wide, rounded and bifid at apex. Stamens 4, 55–77 mm long, distally glabrous, pubescent near base with eglandular trichomes, thecae yellowish green, 6.5–9. 5 mm long; staminode 1, ± triangular, 0.1– 1.5 mm long. Style 60–67 mm long, glabrous, stigma unequally 2-lobed and ± obliquely funnelform, 1.5– 2 mm long, lobes ± elliptic, 1– 1.5 mm long, 0.6– 1 mm wide. Capsule (20–) 23–26 mm long, 4–6 mm in diameter, glabrous, stipe 1.5– 2 mm long. Seeds up to 16 per capsule, 4– 4.5 mm long, 3–4 mm wide, surfaces with subconic to low rounded protrusions or becoming smooth.

PHENOLOGY.— Flowering: January–March; fruiting: February–March, June. In the two populations of this species observed for ca. one hour each, floral buds were present on the plants at both sites during daylight hours (morning for Daniel 8294 and afternoon for Daniel & Butterwick 5905), and mature fallen flowers were present on the ground at one site (Daniel 8294). Likewise, Brewer et al. 7176 notes that the corollas fall in the morning.

DISTRIBUTION AND HABITAT.— East-central Belize ( Belize, Cayo; Fig. 10 ); plants occur on steep limestone slopes in evergreen seasonal forests (tropical evergreen seasonal broadleaf lowland forest fide Meerman and Sabido 2001) at elevations from 10 to 120 m.

ILLUSTRATIONS.— Figure 12; Leonard (1936:197, fig. 1).

CONSERVATION.— Daniel (1997) noted that the population at the type locality had been destroyed by quarrying activities, but that other populations had been located on several of the small, isolated, and steep limestone hills in the southern portion of the coastal plain in Belize District. Louteridium chartaceum has since (i.e., in 2005) been located in Cayo District, as well. Plants occur in at least three protected areas, and the species’ EOO (189 km 2) includes a portion of another one. Ecologist and botanist Steven Brewer (in litt., 14 May 2018) indicates that the species “is common though not abundant on ridge-tops and exposed limestone along the north side of the Maya Mountains in Cayo and Belize districts.” Brewer (in litt., 22 May 2018) also notes that in this region, potential threats to all of the limestone forests include land conversion via agriculture (both in and around protected areas), encroachment or settlement in protected areas, and fire (either natural or “escaping” flames from regular burning used to clear nearby agricultural fields or bush). In the same communication, Brewer also observed that, “ L. chartaceum (though I doubt the same is true for L. donnell-smithii ) is surprisingly resilient from the effects of even very hot fires. Natural light fires are occasional on those limestone hills and so it seems that most species there are tolerant or resilient in the face of light fires.” Scant change in vegetation cover within the EOO is evident from the historical imagery (1969 to 2016) seen via Google Earth Pro (2018). If the three protected areas in which the species occurs are treated either as a single or multiple locations, and the unprotected areas are treated as another location under threat (i.e., conversion of nearby, and partly within the EOO, land to agriculture as an inferred or projected threat), a preliminary conservation assessment of Endangered (EN; B1, a, b) can be proposed for L. chartaceum .

DISCUSSION.— Plants grown in San Francisco from cuttings of Louteridium chartaceum from the type locality (Daniel & Butterwick 5905cv) produced floral buds that attained 35 mm in length but abscised prior to opening. Both thyrses and racemose thyrses are present on Brewer et al. 7176. Bracteoles of a pair are sometimes fused basally for about 1 mm, at least along one side.

ADDITIONAL SPECIMENS EXAMINED.— BELIZE. Belize: Runaway Creek Nature Reserve , E of Coastal Road, 17°18’44”N, 088°27’23”W, S . Brewer et al. 7176 (MO-image seen); along Coastal Hwy. near milepost 18, ca. 5 km W of Gales Point toward La Democracia, ca. 17°11’N, 088°22’W, T . Daniel 8294 ( BR, CAS, MEXU, MICH, MO, US) ; Gracie Rock Hill near Rockville Quarry between Western Hwy. and Sibun River , ca. 30 km SW of Belize City [ca. 17°23’13.67”N, 088°27’1.91”W], T . Daniel & M . Butterwick 5905 ( C, CAS, K, MICH, MO, NY), cultivated plants of this collection grown from cuttings in San Francisco, California, 5905cv ( CAS); Gracie Rock, 1.5– 4 mi S of Mile 22 on Western Hwy. , J . Dwyer 10959 ( LL, MEXU, MO), R . Liesner & J . Dwyer 1485 ( BM, DUKE, MO, NY, TEX). Cayo: Manatee Forest Reserve, Banks of Indian Creek , at confluence of Yaha and Indian Creek , 1 km W from Daylight Cave , 17°12’54.2”N, 088°33’19.4”W, H . Baden & D. Harris 3 ( BM) .

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.