Mendoncia delphina Magnaghi, Novon

Magnaghi, Emily B. & Daniel, Thomas F., 2017, Systematics of Mendoncia (Acanthaceae: Thunbergioideae) in the Paleotropics, Proceedings of the California Academy of Sciences 64 (3), pp. 37-94 : 65-66

4. Mendoncia delphina Magnaghi, Novon 23:190. 2014.

TYPE.— MADAGASCAR. Toliara: NW of Taolagnaro (Ft. Dauphin), Parc Natl. Andohahela, Réserve integral no. 11, parcel 1, E boundary, 24°45ʹS, 46°51ʹE, 250–500 m, 17–20 Oct 1992, Malcomber et al. 1665 (holotype: MO-05003406!; isotypes: K, TAN) .

Young stems glabrous to mealy-glandular or sometimes pubescent with sparse, whitish to yellowish, antrorsely appressed, unbranched, eglandular trichomes 0.05– 0.5 mm long. Leaves subcoriaceous, petioles to 14 mm long, glabrous or pubescent like young stems, blades elliptic to ovate-elliptic, 44–83 mm long, 15–34 mm wide, acute to cuneate at base, caudate (with tail-like extension to 12 mm long) to acuminate at apex, surfaces glabrous to mealy-glandular. Inflorescence borne in leaf axils on young, mostly herbaceous, and leafy stems, solitary or opposite at nodes, dichasia 1–2 per axil, peduncles to 40 mm long, glabrous or pubescent like young stems. Bracteoles yellowish, deciduous by time of fruit maturation, ovate to elliptic, 6. 9–14 mm long, 5.3–8. 3 mm wide, rounded to truncate at base, acute at apex, abaxial surface glabrous or with a few short trichomes to 0.3 mm long, adaxial surface mealy glandular and very densely but minutely (trichomes ˂ 0.05 mm long) pubescent at apical tip. Calyx glabrous or sparsely pubescent with unbranched eglandular trichomes 0.05 mm long (sometimes restricted to margin). Corolla (purplish) white with purple throat, 16.1–18. 5 mm long, externally and internally mealy-glandular, tube 7.6–9. 3 mm long, limb 14–18 mm in diameter, upper lip 7.2–9. 1 mm long with rounded lobes 5.3– 6. 6 mm long and 4.5– 5.8 mm wide, lower lip 8.5–9. 5 mm long with rounded lobes 5–8. 5 mm long and 3.5– 5.7 mm wide. Stamens 8.5–8. 8 mm long, ventral pair inserted 0.5 mm distal to the dorsal pair, filaments mealy-glandular proximally, thecae 4– 4.3 mm long, densely pubescent at base with a tuft of bristles 0.1– 0.2 mm long, these sometimes extending distally on thecae, connective extending 0.6– 1 mm beyond thecae, extension of connective attenuate, glabrous, staminode 2 mm long. Pollen 5-colpate, E = 36–37 µm, P = 35–37 µm, P:E = 0.968–1.00, C = 8.7–10.6 µm, C: P = 0.248–0.302, rugulae microverrucate to microgemmate. Style 11–12. 3 mm long, glabrous, stigma subequally to unequally 2-lobed, lobes 0.1– 0.8 mm long. Drupe (immature?) ovoid-ellipsoid, 13.5 mm long and 9 mm diameter, glabrous to mealy-glandular.

PHENOLOGY.— Flowering: October–November; fruiting: November.

DISTRIBUTION AND HABITATS.— Extreme southeastern Madagascar (Toliara; EOO = 134 km 2; Fig. 12 ). Plants occur in lowland, moist to wet, evergreen forests near Taolagnaro. Elev. 250–500 meters.

ILLUSTRATION.— Magnaghi and Daniel (2014:192, Fig. 2 ).

Corollas of Mendoncia delphina resemble those of M. flagellaris in color (white with purple markings on the limb and throat), and its flowering period concurs with that species. The distribution of M. delphina overlaps those of both M. cowanii and M. flagellaris , but appears to be restricted to the southeastern-most Madagascar. The leaves of M. delphina are consistently elliptic with an acuminate apex and a unique venation pattern with the secondary veins branching from the midvein at angles of 35 to 45 degrees. A fruiting collection of M. flagellaris (Ravelonarivo & Rabesonina 741) from Antsiranana in northern Madagascar has leaves similar to those of M. delphina in both of these attributes. The identity of this collection, which lacks flowers, remains uncertain.

ADDITIONAL SPECIMENS EXAMINED.— MADAGASCAR. Toliara: Préfecture de Fort Dauphin, Forêt Manantantely , [ca. 24°59ʹS, 046°55ʹE], Dumetz 1395 ( MO); NW of Taolagnaro ( Fort Dauphin ), RNI #11 ( Andohahela ), parcel 1, eastern boundary, [ca. 24°42ʹS, 46°44ʹE], Malcomber et al. 1665 ( MO).

Figures

FIGURE 12. Map of Madagascar showing distributions of Mendoncia decaryi and M. delphina, and map of Madagascar and Mayotte showing distribution of M. flagellaris.

FIGURE 2. Domatia on abaxial surfaces of leaves of Mendoncia cowanii var. cowanii. A. Daniels 98. B. Daniel et al. 9116. C, D. Scanning electron micrographs of Daniel et al. 9116 showing intertwined trichomes in axils of midvein with secondary vein.