Louteridium koelzii Miranda & McVaugh, Ann. Inst. Biol. Mex.

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 : 85-88

6. Louteridium koelzii Miranda & McVaugh, Ann. Inst. Biol. Mex. 32:182. 1962 (“1961”). TYPE.— MEXICO. Jalisco: 8 mi SW of Pihuamo [ca. 19°11’26.09”N, 103°28’3.97”W], 500-600 m, 6-XII-1959 (flr), R . McVaugh & W . Koelz 1507 (holotype: MICH!; isotype: MEXU!) .

Trees to 10 m tall. Older (woody) stems subquadrate, irregularly fissured-striate; younger (herbaceous) stems stubby, quadrate, glabrous. Leaves deciduous, clustered at apex of old growth, petiolate, petioles to 73 mm long, blades membranaceous, ovate to elliptic, 90–220 mm long, 35–100 mm wide, 2–2.7 × longer than wide, acute to acuminate at apex, rounded to attenuate and asymmetric at base, surfaces glabrous, margin entire. Inflorescence of axillary and/or terminal subsessile to pedunculate thyrses (main axis with lateral pedunculate dichasia appearing as branches) to 250 mm long, peduncle to 50 mm long, pubescent with erect to flexuose eglandular trichomes 0.05–0.2 (–1) mm long, rachis pubescent with erect to flexuose eglandular trichomes 0.1–0.4 (–1) mm long; dichasia opposite, pedunculate, 1–3 (or more)-flowered, to 63 mm long (excluding corollas), dichasial peduncles 3–20 mm long, pubescent like rachis. Bracts caducous, lance-elliptic to elliptic, 12–17 mm long, 3.5– 5 mm wide, abaxially pubescent with erect to flexuose eglandular trichomes 0.05– 0.2 mm long. Bracteoles and secondary bracteoles usually present on young inflorescences but becoming deciduous as inflorescence matures, lance-elliptic to elliptic, 7–14 mm long, 2–3. 5 mm wide, abaxially pubescent like bracts. Flowers pedicellate, pedicels 10–50 mm long, pubescent like rachis. Calyx 17–28 mm long, lobes subheteromorphic, membranaceous, abaxially pubescent with erect (to ± antrorse) eglandular trichomes 1–2 (–2.3) mm long, posterior lobe planar to ± conduplicate, ovate-elliptic, 17–25 mm long, 11–15 mm wide, usually slightly larger than lateral lobes, acuminate at apex, lateral lobes ovate-elliptic to elliptic to obovate, 15. 5–22 mm long, 9–15 mm wide, rounded to acute at apex, veins of lobes prominent (ca. 9 major veins). Corolla “pale green” to greenish yellow, 50–55 mm long, externally glabrous, tube 29–33 mm long, narrow proximal portion 9–13 mm long, 9–16 mm in diameter near midpoint, throat 15–20 mm long, 30–35 mm in diameter at mouth, lobes spreading to recurved, “narrowly ovate to subcircular” (fide Miranda and McVaugh 1962), 18–24 mm long, 17–27 mm wide, round- ed to acute at apex. Stamens 4, 72–90 mm long, filaments glabrous distally, pubescent proximally with eglandular trichomes, thecae 10–12 mm long; staminode (if present) not seen. Style 50–55 mm long, glabrous, stigma lobes 1.5 mm long, shape and width not determined. Capsule 25–30 mm long, 7–10 mm in diameter, pubescent throughout with erect to flexuose to antrorse eglandular trichomes 0.05– 0.2 mm long, stipe 1.5– 2 mm long. Seeds up to 16 per capsule, 7–8 mm long, 5–6 mm wide, surfaces minutely papillose.

PHENOLOGY.— Flowering: December–February; fruiting: February.

DISTRIBUTION AND HABITAT.— West-central Mexico (Jalisco, Michoacán; Fig. 8 ); plants occur on limestone slopes in “high forest dominated by Brosimum ” in regions of tropical subdeciduous and deciduous forests at elevations from 500 to 1400 meters.

ILLUSTRATIONS.— Figure 14 ; Miranda and McVaugh (1962:183, fig. 2).

CONSERVATION.— Louteridium koelzii is currently known from a very limited region of western Mexico ( EOO = 5.3 km 2; AOO = 12 km 2). The species is not known to occur in a protected area, and it has not been recollected since 1975 (i.e., McVaugh 26180; although see discussion below about an undetermined plant from a nearby region of Jalisco). Based on current knowledge, there appear to be two subpopulations about 80 km apart, one in Jalisco and one in Michoacán. Comparing historic landsat images (2006 to 2017) via Google Earth Pro (2018) in the region of the known collections from Jalisco, it is evident that deforestation for agriculture has reduced the natural vegetation there substantially (ca. ≥ 30%), thus creating a threat to this species, at least in that region. No specific threat has been identified for the subpopulation in Michoacán. Thus , there are two locations for the species, and a threat is evident for one of them. Based on these observations, a preliminary conservation assessment of Endangered ( EN; B1 , a, b) is proposed for L. koelzii .

DISCUSSION.— An undetermined specimen of Louteridium from western Mexico (Jalisco: Mpio. Jilotlán de los Dolores, Cerro de San Antonio, 15 km N de Tazumbos, matorral subtropical en suelos con pedregocidad de toba volcánica, 900 m, 6 Feb 1982, F. Santana Michel 1081, IBUG) does not seem to pertain to either species known from nearby regions (i.e., L. brevicalyx or L. koelzii ) or other species of the genus. The plant, which lacks mature flowers, is geographically closest and morphologically most similar to L. koelzii . Like that species, it occurs in an apparently dry habitat and has seasonally deciduous foliage. Both of these characteristics suggest that the undetermined plant has four stamens. Other characteristics in common with L. koelzii include erect to flexuose eglandular trichomes on the rachis, peduncles, and pedicels; ovate-elliptic calyx lobes, and externally glabrous corollas. It differs from specimens of L. koelzii studied herein by having pubescent young stems, shorter calyces (14–15 mm long, although the flowers are not fully mature), and longer (35–40 mm) capsules that are pubescent only at the apex. Disposition of this plant awaits further studies and/or collections.

ADDITIONAL SPECIMENS EXAMINED.— MEXICO. Jalisco: ca. 12–13 km SW of Pihuamo , R . McVaugh 26180 ( MICH); 8 mi SW of Pihuamo, R . McVaugh & W . Koelz 1797 ( MEXU, MICH, US) . Michoacán: 15–16 km SE of Aserradero Dos Aguas, W of Aguililla [ca. 18°45’51.11”N, 102°49’22.26”W], R . McVaugh 24740 ( MICH) .

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.

FIGURE 14. Louteridium koelzii. A. Apex of shoot with flush of new leaves (McVaugh & Koelz 1797). B. Branch with inflorescence in flower (McVaugh & Koelz 1507). C. Leaf (McVaugh & Koelz 1797). D. Corolla bud opened (McVaugh & Koelz 1797). E. Dehisced corolla with epipetalous stamens (McVaugh 26180). F. Distal portion of style and stigma (McVaugh 26180). G. Partially dehisced capsule with calyx and pedicel (McVaugh 26180). H. Seed (McVaugh 26180). Drawn by Karin Douthit, copyright reserved to University of Michigan Herbarium, used with permission.