Psychotria ambatovensis C.M. Taylor, 2020

Taylor, Charlotte M., Gereau, Roy E. & Schmidt, Heidi H., 2020, Some distinctive new species of Psychotria (Rubiaceae, Psychotrieae) from Madagascar, Candollea 75 (2), pp. 159-182 : 161-162

Psychotria ambatovensis C.M. Taylor , sp. nov. ( Fig. 1A–F ).

Holotypus: MADAGASCAR. Reg. Alaotra-Mangoro [Prov. Toamasina] : Moramanga , Ambohibary , Ampitambe , 18°50'17"S 48°15'44"E, 975 m, 24.II.2009, Andriamiarinoro et al. 164 ( MO-6416482 !; isotype: P, TAN) .

Psychotria ambatovensis C.M. Taylor is distinguished from P. macrochlamys (Bremek.) A.P. Davis & Govaerts by its smaller leaves, subsessile subcapitate inflorescences, and calyx limbs that are pubescent externally (i.e., abaxially).

Shrubs and small trees, collected in flower at 2–6 m tall, branched; stems flattened, smooth or with shallow medial channel, densely hirtellous with trichomes 0.3–1.2 mm. Leaves opposite; petiole 0.3–1.8 cm, densely hirtellous with trichomes 0.3–1.2 mm; blade obovate to elliptic, 1.5–6.5 × 0.8–5 cm, at base acute to obtuse or rounded, at apex obtuse to rounded, truncate, or shallowly retuse, drying chartaceous to subcoriaceous, adaxially weakly bullulate to plane, shiny, and glabrous, abaxially densely hirtellous with trichomes 0.3 – 1.2 mm; secondary veins 4 to 10 pairs, looping to interconnect near margins, apparently without domatia, without intersecondary veins or sometimes with 1 short vein arising from costa between a pair of secondary veins, adaxially costa and secondary veins impressed, tertiary venation plane to impressed or thinly prominulous, and remaining venation not visible, abaxially costa and secondary veins prominent and loosly reticulated tertiary and quaternary venation prominulous. Stipules calyptrate, caducous, in bud fully fused into a conical or ovoid cap, 6–18 mm, acute at top, splitting along 1 or 2 sides then separating from stem at base, abaxially (i.e., externally) densely hirtellous with trichomes 0.3– 1.2 mm, adaxially (i.e., internally) densely to sparsely hirtellous with trichomes 0.5 –1.5 mm. Inflorescences terminal, subcapitate, subsessile, subglobose, 3- to 7-flowered, initially enclosed by a calyptrate, caducous stipule 10–18 mm; bracts 2 or 4, stipuliform, 4–6 mm. Flowers all subsessile, at base surrounded by dense ring of pilose or strigose trichomes 1–2 mm, 4-, 5-, or 6-merous; hypanthium cylindrical to ellipsoid, 1 – 1.5 mm, densely strigose to hirtellous with trichomes 0.5–1.5 mm; calyx limb c. 2 mm, externally hirtellous to strigose with trichomes 1– 1.5 mm, internally glabrous, lobed for 1/4–1/2 of its length, lobes narrrowly triangular to linear; corolla funnelform, yellow, externally glabrous or moderately to densely strigose on top part of tube and base of lobes with trichomes 0.5–1 mm, tube 4.5–5 mm, c. 1.5 mm diam. near middle, internally glabrous except densely tomentulose with trichomes 0.3–0.5 mm at top of tube (i.e., in throat), lobes narrowly triangular, 2–2.5 mm, acute, adaxially shortly galeate, abaxially with rounded thickening near apex; stamens with filaments c. 1 mm, inserted in uppermost part of tube, anthers oblong, c. 0.8 mm, exserted; style and stigma not seen. Infructescences similar to inflorescences. Young fruits ellipsoid, c. 6 × 5 mm, densely strigose to hirtellous with trichomes 1–1.5 mm, with calyx often enlarging, to 4 mm, when mature not seen but reportedly orange to red; pyrenes hemispherical, adaxially plane, abaxially apparently smooth; endosperm deeply and densely ruminate on all sides.

Habitat, distribution, and phenology. – Psychotria ambatovensis has been collected in humid evergreen forest at 974–1180 m in east-central Madagascar (Toamasina), with flowers in February and March, and with fruits in July .

Conservation status. – Psychotria ambatovensis is known from five specimen collections representing five unique occurrences in humid evergreen forest. Two occurrences are within the mine footprint of the Ambatovy nickel-mining project, and have been removed from the dataset for the calculation of assessment parameters. The Extent of Occurrence (EOO) of the species is 18 km ², within the limits for “Critically Endangered” under IUCN Red List Criterion B1; and the Area of Occupancy (AOO) is 12 km ², within the limits for “Endangered” under Criterion B2 ( IUCN, 2012). One occurrence is within the well-protected Mantadia Protected Area (PA), and the other four occurrences are in areas to the west of the Park: three in Analamay Forest (with one label indicating “conservation zone”), and one in a “degraded forest patch” at Ankoditrazo. Forested areas without formal protection in the vicinity of Mantadia PA are subject to degradation by small-scale slash and burn agriculture ( GOODMAN et al., 2018). Two of the sites within Analamay Forest are within the mine footprint of the Ambatovy nickel-mining project, while the third is within the adjacent conservation zone. After removal of the two collection sites on the mine footprint, which have aleady been destroyed, three locations (sensu IUCN, 2012; see also IUCN, 2019) can be defined relative to the known threats: the degraded site at Ankoditrazo; the one protected site within the Ambatovy conservation zone; and the one protected site within Mantadia PA. With three locations, given general habitat degradation in unprotected sites with the westernmost location at Ankoditrazo likely to disappear in the near future, causing a decline in EOO, AOO, number of locations, and number of mature individuals, the Red List status of P. ambatovensis is assessed as “Endangered” [EN B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)].

Notes. – Psychotria ambatovensis is characterized by the combination of its dense hirtellous to hirsute pubescence on both vegetative and reproductive structures; relatively small obovate leaf blades that are obtuse to truncate at the tip; caducous calyptrate stipules; subsessile, subcapitate, few-flowered inflorescences; lobed, rather well developed calyx limbs; rather small yellow corollas; rather small fruits; and endosperm that is ruminate on both surfaces. The plants dry with a dark brown or reddish brown color, with the dried trichomes deeply reddish brown to brown. The leaves are often weakly bullulate. This species apparently lacks acarodomatia on the leaves, although the dense pubescence of the abaxial vein axils may have this function. The flowers seen have variously four to six lobes and anthers, with the number apparently consistent on an individual plant. The few flowers seen agree with the short-styled form of distylous Psychotria species , but whether this species is distylous is not yet known. The fruits seen appear to be young, and the smooth young pyrenes of some species develop ridges as they mature ( TAYLOR, 2020) and this is a possibility here. The characters of P. ambatovensis place this in BREMEKAMP (1963) ’s Mapouria Group VI. Its calyptrate stipules are supposedly anomalous in his group but were actually overlooked in several of its species, including P. macrochlamys (Bremek.) A.P. Davis & Govaerts ( TAYLOR, 2020) .

Psychotria ambatovensis is similar to P. macrochlamys , which differs in its larger leaf blades 8–22 × 4.5–17 cm, fasciculate to pedunculate, branched inflorescences, and calyx limbs that are glabrous externally. Psychotria ambatovensis is also similar in aspect to P. reducta Baker , which differs in its glabrous to sparsely hirtellous stems and leaves, leaf blades with regularly developed acarodomatia, interpetiolar, bilobed, shorter stipules 3–5 mm long, and pedunculate branched inflorescences.

Paratypi. – MADAGASCAR. Reg. Alaotra-Mangoro [ Prov. Toamasina ]: Moramanga , Andasibe , Ambatovy , forêt d’Analamay , 18°49'21"S 48°20'07"E, 3–5.II.2005, Andriatsiferana et al. 2531 ( MO, P, TAN); ibid. loco, 18°48'38"S 48°20'41"E, 1151 m, 27.VI.2008, Antilahimena et al. 6408 ( MO, P, TAN); ibid. loco, 18°49'13"S 48°20'06"E, 1180 m, 2.II.2005, Razafindraibe & Antilahimena 7 ( MO, P, TAN); Mantadia National Park , 18°49'03"S 48°26'03"E, 1080 m, 1.III.2011, Razafimandimbison et al. 1095 ( MO, S) .

Figures

Fig. 1. – Psychotria ambatovensis C.M. Taylor: A. Flowering branch; B. Stem apex with bases of two petioles and stipules in process of dehiscence; C. Hypanthium and calyx limb of flower; D. Corolla at anthesis; E. Fruit; F. Cross-section of pyrene and seed. Psychotria eumachioides C.M. Taylor: G. Fruiting branch; H. Stem apex with stipule and basal part of two petioles; I. Portion of stem below leaves with two nodes, stipules (upper node), and stipule scar (lower node); J. Portion of inflorescence with three flowers from which corollas have fallen and one flower at anthesis; K. Cross-section of pyrene and seed. Psychotria notopleuroides C.M. Taylor: L. Flowering stem and part of basal prostrate stem; M. Portion of inflorescence with two flower buds and one flower at anthesis; N. Cross-section of pyrene and seed. [A–D: Andriamiarinoro 164; E–F: Antilahimena 6408; G, K: Rabehevitra 1059; H–J: De Block 1172; L: Schatz et al. 3666; M: Labat & Andrianjafy 3377; N: Zjhra & Hutcheon 378]