Louteridium dendropilosum T.F. Daniel, Proc. Calif. Acad. Sci.

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 : 77-79

4. Louteridium dendropilosum T.F. Daniel, Proc. Calif. Acad. Sci. 64:140. 2017. TYPE.— MEXICO. Oaxaca: Distr. Pochutla, Mpio. San Miguel del Puerto, Arroyo Arena, ca. 100 m downstream from jct. Río Laja , ca. 3 km SE of Rancho Dioon toward Xadani , 15°58’51.33”N, 096°05’53.91”W, 600 m, evergreen seasonal forest (selva mediana subperennifolia), 29-III-2011, T. Daniel, A. Sánchez, and J. Pascual 11784 (holotype: MEXU!; isotypes: CAS! COLO! K! MO! NY! SERO! US!) .

Shrubs to trees to 12 m tall, sometimes epipetric. Older (woody) stems quadrate, lenticellate, irregularly striate-sulcate, lacking trichomes; younger (herbaceous) stems subquadrate-sulcate, sparsely lenticellate, irregularly fissured, evenly pubescent with erect to flexuose simple and dendritic (sparse) eglandular trichomes <0.1– 0.5 mm long. Leaves seasonally deciduous, ± clustered at apex of old growth or at apex of an otherwise leafless shoot of new growth, petiolate, petioles to 65 mm long, blades subsucculent, ovate to elliptic to broadly elliptic, 76–190 mm long, 40–122 mm wide, 1.4–2.5 × longer than wide, apiculate to acuminate at apex, rounded to acute to attenuate at base, adaxial surface pubescent with simple and dendritic eglandular trichomes, trichomes soon becoming ± restricted to proximal portion or to midvein, abaxial surface pubescent (especially along veins) with dendritic trichomes to 0.5 mm long, midvein often pinkish or reddish, margin entire (sometimes undulate and appearing subcrenate). Inflorescence a terminal subsessile to pedunculate raceme to 220 mm long, peduncle to 50 mm long, pubescent like young stems, rachis pubescent like young stems; dichasia opposite or alternate, sessile, 1-flowered, to 47 mm long (excluding corollas). Bracts caducous, lanceolate to lance-ovate, 11–16 mm long, 2. 5–6 mm wide, abaxially pubescent with simple and dendritic trichomes 0.05– 0.2 mm long. Bracteoles caducous, lanceolate to lance-elliptic, 7–9 mm long, 2–3 mm wide, abaxially pubescent like bracts. Flowers pedicellate, pedicels 21–46 mm long, pubescent like rachis or with the trichomes to 1 mm long. Calyx 17–32 mm long, lobes fused at base for 1– 1.5 mm, subhomomorphic to subheteromorphic, membranaceous, subelliptic to ovate-elliptic to subrhombic-obovate, rounded to acute at apex, abaxially pubescent with mostly dendritic trichomes 0.1– 0.5 mm long, posterior lobe planar, 17–32 mm long, 10–19 mm wide, usually slightly larger and sometimes more conspicuously venose than lateral lobes, major veins often maroon, lateral lobes 20–31 mm long, 8–18 mm wide. Corolla light green or greenish yellow, sometimes with maroon on limb (especially at base of lobes) and distal portion of throat, externally glabrous (inconspicuously glandular punctate but lacking elongate trichomes), 50–62 mm long, tube 35–37 mm long, narrow proximal portion 11–15 mm long, 6–10. 5 mm diameter near midpoint, throat 20–24 mm long, 25–35 mm diameter at mouth, lobes recurved to recoiled, broadly ovate to subtriangular, 13–20 mm long, 10–21 mm wide, entire at apex. Stamens 4, 60–80 mm long, filaments glabrous distally, glabrous or pubescent with eglandular trichomes near base, thecae 8–10. 5 mm long; staminode 1, rodlike, 0. 6–40 mm long. Style 70–101 mm long, distally glabrous, pubescent with eglandular and glandular trichomes near base, stigma equally 2-lobed, lobes broadly elliptic to broadly ovate-triangular, 1–2 mm long, 1– 1.4 mm wide. Capsule 21–28 mm long, 6.5–9. 5 mm in diameter, densely pubescent with erect glandular trichomes 0.05– 0.5 mm long and with an overstory (sometimes sparse) of erect to flexuose (sometimes dendritic) eglandular trichomes to 1.4 mm long, stipe 2.5– 3.5 mm long. Seeds up to 16 per capsule, 5. 2–7 mm long, 5–6. 4 mm wide, surfaces smooth.

PHENOLOGY.— Flowering: February–March; fruiting: March–April. Based on field observations and cultivated plants (Daniel et al. 11894cv), flowering occurs on leafless (or nearly leafless) plants during the dry season. Near the end of the dry season (e.g., late March–April) when flowering is waning and fruits are mature, a new flush of vegetative growth appears from axils of clustered leaf scars at the base of the inflorescence, which eventually falls away. New internodal stem elongation (e.g., the young stems of the description above) takes place from the axil of a leaf scar on the old growth and terminates in a cluster of new leaves and/or between at least one of the pairs of leaves in the cluster and the remaining cluster.

Field observations of Daniel et al. 11894 over three days (24–26 February 2012) revealed: day 1 between 08:00–09:00 (light) — corollas mostly fallen, only a few from previous night still attached to tree; day 2 between 19:00–20:00 (dark) — all corollas open, ca. 100 seen, bats active around plants but none seen visiting flowers, no floral odor detected and no nectar visible in saccate tube of undissected corollas, stigma extended ca. 1 cm beyond anthers on fresh flowers, stigma of 7 flowers examined for pollen (all pollinated); day 3 between 17:30–18:30 (light) — many corollas open and many others still in bud, corollas open fully (including recurving of corolla lobes) in 15 to 20 seconds, open flowers actively visited by Cinnamon Hummingbird ( Amazilia rutila , species det. by Jeff Chemnick), birds probe for nectar once or twice at same flower before moving on, nectar is located behind a barrier (seen in dissected flowers) at the base of the tube, nectar not visible in the saccate throat, birds appear to contact anthers with head or back and presumably contact the stigma on some visits as well, birds visit between 5–10 flowers on a single plant or on multiple plants before moving away from an area or resting on a branch, 2 flowers were observed to open and when subsequently visited by a hummingbird (one flower visited once, other flower visited twice) they were checked for pollination (no pollen observed on stigma of either), small bees or flies also observed visiting flowers but they only contact anthers, buds continue opening until full darkness (at 18:30); day 3 between 18:30–20:30 (dark) — hummingbirds no longer active, bats very active around plants but none observed visiting flowers.

On a single flower of Daniel et al. 11894cv grown in San Francisco, corolla lobes began to separate at 15:50 and the corolla was fully open (lobes spreading 90° with respect to the throat or reflexed) with the stamens and style fully exserted by 16:15. By 18:00, all corolla lobes were at least partially recoiled. At 23:00, 6.5 μl of nectar was encountered in the nectar chamber, and the stigma was dusted with pollen from the anthers. At 07:15 the next day, 72.1 μl of nectar was recovered from the nectar chamber. The corolla abscised and fell from the persisting flower at 07:45. Thus, the corolla of the pollinated flower persisted for ca. 16 hours.

DISTRIBUTION AND HABITAT.— Southern Mexico (Oaxaca; Fig. 8 ) in the Sierra Madre del Sur and the Isthmus of Tehuantepec ; plants occur on limestone (often karstic) slopes of streams in tropical deciduous forests and tropical subdeciduous forests at elevations from 600 to 750 m.

ILLUSTRATIONS.— Figure 2F–L; Daniel (2017:143, fig. 8).

CONSERVATION.— A discussion and preliminary conservation assessment of Endangered (En) was proposed for this species (B1, a, b; IUCN 2017) by Daniel (2017).

DISCUSSION.— Louteridium dendropilosum is unique among congeners by its dendritic trichomes, which are present on both vegetative and reproductive organs. Trichomes of other species may consist of one or more cells and be either glandular or eglandular, but they are not branched. Bracts and bracteoles are caducous prior to maturation of the flowers associated with them; thus, they are rarely encountered and are not present on any of the wild-collected specimens. The data on their shape, size, and pubescence noted above were taken just prior to their dehiscence from the young inflorescence of a cultivated plant (Daniel et al. 11894cv).

ADDITIONAL SPECIMENS EXAMINED.— MEXICO. Oaxaca: Distr. Pochutla, Mpio. San Miguel del Puerto, Arroyo Arena , ca. 100 m downstream from jct. Río Laja , ca. 3 km SE of Rancho Dioon toward Xadani , 15°58’51.33”N, 096° 05’53.91”W, T . Daniel, et al. 11894 ( CAS, MEXU), 12187 ( CAS, MEXU), cultivated plants of 11894 grown from seeds in San Francisco, California , 11894cv ( CAS); Mpio. El Barrio, 9 km N [sic] de El Barrio, Cerro Palmasola , antena microondas [ca. 16°44’32.52”N, 095°05’36.04”W], R . Fernández N . 4189 ( IEB, NY); Distr. Pochutla, Mpio. San Miguel del Puerto , Arroyo Arena, 15°58’39.7”N, 096°05’54.9”W, J . Pascual 1396 ( MEXU, SERO, TEX); Distr. Pochutla, Mpio. San Miguel del Puerto, 300 m de la terracería sobre la vereda rumbo Río la Laja , 15°58’49.9”N, 096°06’6.9”W, A . Saynes V . et al. 3831 ( MEXU, SERO); Distr. Juchitán, Mpio. El Barrio, parte alta del Cerro Palmasola, junto a la antena de microondas [ca. 16°44’32.52”N, 095°5’36.04”W], S . Zamudio R . 6352 (CAS, IEB).

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.