Acalypha inaequibracteata I.Montero & Cardiel, 2023

Montero-Munoz, Iris, Levin, Geoffrey A., Vaquero Lorenzo, Concepcion, Gonzalez, Laura & Cardiel, Jose M., 2023, Novelties in the genus Acalypha (Euphorbiaceae, Acalyphoideae): two new species from northern Madagascar, Plant Ecology and Evolution 156 (3), pp. 365-373 : 365

Acalypha inaequibracteata I.Montero & Cardiel sp. nov.

Fig. 3

Type.

MADAGASCAR - Sava region [Antsiranana prov.] • Vohimarina district, Vohemar sub-prefecture, rural municipality of Daraina , Binara forest ; 13°15.42'S, 49°36.8'E; 440 m; 22 Dec. 2003; Nusbaumer L. LN875; holotype: G [G00006971]; isotype: P [P04786262] .

Diagnosis.

Acalypha inaequibracteata is morphologically similar to A. ankaranensis I.Montero & Cardiel, but differs mainly by having minute stipules up to 2 mm long, with simple trichomes (vs. stipules up to 5 mm long, with simple and glandular trichomes), petioles 0.5-1(-1.5) cm long (vs petioles 3-5 cm long), ovate to elliptic-lanceolate leaf blades that are rounded to obtuse at the base and lack domatia (vs broadly ovate-lanceolate leaf blades that are subcordate to cordate at the base and have pocket-shaped domatia), and dimorphic female bracts (vs monomorphic female bracts).

Description.

Shrubs, probably deciduous, 0.2-0.3 m tall, monoecious. Branches pubescent with short, antrorsely curved, simple, trichomes, glabrescent when mature. Axillary buds inconspicuous. Stipules inconspicuous, up to 1.5-2 mm long and 0.5 mm wide at base, triangular-lanceolate to linear-lanceolate, sparsely hairy with minute simple trichomes up to 0.2 mm long. Petioles thin, 0.5-1(-1.5) cm long, indumentum similar to that on young branches. Leaf blades (3-)4-5(-6) × 1.5-2(-2.7) cm, ovate to elliptic-lanceolate, membranous; base rounded to obtuse; apex acute to acuminate, acumen mucronate; margins crenate to serrate, teeth minute with small, sessile, glandular trichomes at apex; upper surface laxly pubescent with sparse, erect, simple trichomes up to 1 mm long and antrorsely curved trichomes on veins; lower surfaces with indumentum similar to that on the upper surface but less dense; venation actinodromous, basal veins 3(-5), secondary veins 4-5 per side. Stipels absent. Inflorescences spiciform, androgynous, and solitary female bracts, mainly axillary, some androgynous inflorescences terminal in lateral branches. Androgynous inflorescences up to 5.5 cm long; peduncle up to 0.8 cm long, indumentum similar to that on young branches; female segment up to 3 cm long, bracts 2-5, sessile, enlarging in fruit, dimorphic on the same plant (broadly ovate-lanceolate to subtriangular, up to 10 × 10 mm, on some inflorescences and oblate, up to 11 × 6.5 mm, on other inflorescences), both sparsely hairy with simple trichomes on both surfaces, oblate bracts also with minute glandular trichomes on lower surface; margin crenate to subentire, with minute, sessile, glandular trichomes at tooth apices, central tooth not prominent, bracteoles up to 0.6 mm long, triangular, sparsely hairy; usually there are inflorescences with all the bracts of the female segment oblate and other inflorescences with all the bracts of the female segment ovate-lanceolate to subtriangular; male segment persistent, up to 2.5 cm long, flowers glomerulate, bracts up to 0.5 mm long, triangular, sparsely hairy. Solitary female bracts mostly broadly ovate-lanceolate to subtriangular, similar to those found on androgynous inflorescences. Male flowers with pedicel up to 0.5 mm long, glabrous; buds up to 0.5 mm diameter, sparsely hairy, papillose. Female flowers 1 per bract, sessile; sepals 3, up to 0.7 mm long, distinct, triangular, ciliate with minute simple trichomes up to 0.2 mm long; ovary ca 1 mm diameter, 3-lobed, densely papillose-hispid, each papilla ending in a long, hyaline trichome up to 1 mm long; styles 3, up to 6 mm long, distinct, each divided into 6-7 very slender segments, sparsely hairy. Allomorphic flowers not seen. Capsules (immature) up to 2 mm diameter, papillose-hispid, each papilla ending in a simple trichome up to 1 mm long, surface pubescent with simple, minute trichomes. Seeds not seen.

Etymology.

The specific epithet refers to the presence of female bracts showing different shapes.

Distribution and habitat.

Acalypha inaequibracteata is known only from the Binara forest, in Daraina commune, Sava region, at 440 m elevation. The Binara forest is located in north-eastern Madagascar. Acalypha inaequibracteata grows on secondary grassland at the edge of the dense humid semi-deciduous forest, on rough boulders. (Fig. 4 ).

Preliminary IUCN conservation assessment.

Acalypha inaequibracteata is only known from a single collection and location. The extent of occurrence (EOO) could not be calculated. Its area of occupancy (AOO) is estimated to be 4 km2. The Binara forest belongs to the network protected area of Loky-Manambato (Category V; Dudley 2008) and still is relatively well preserved but recently, human activities are affecting the habitat where A. inaequibracteata occurs. The main current threats to the site are subsistence farming and fires to clear land for grazing, logging, and mining ( Rakotondravony 2006; Goodman et al. 2018; BirdLife International 2003). Due to these threats, A. inaequibracteata could be affected in the near future and we do not know if this species grows in other nearby areas. The presumably continued degradation of the habitat lead us to assess A. inaequibracteata as Critically Endangered: CR B2ab(ii,iii,iv).

Note.

We found a specimen at K labelled L. Nusbaumer LN875, thus belonging to the same collection series at G and P. However, the specimen at K corresponds to Acalypha lamiana (Leandri) I.Montero & Cardiel, a species distinctly different from A. inaequibracteata. The original label is on the specimen at G and the specimens were distributed from there, so the K specimen is most likely mislabelled.

Figures

Figure 3. Acalypha inaequibracteata. A. Flowering branch. B. Detail of lower leaf surface. C. Detail of node, stipules, and petiole base. D. Mature female bract. E. Detail of androgynous inflorescence. F. Capsule (immature) and styles. G. Calyx of the female flower. Based on M. L. Nusbaumer LN 875 (G and P). Illustration by Laura Gonzalez Hernandez.

Figure 4. Distribution map of Acalypha bardotiana and A. inaequibracteata. Map created with QGIS (2023).