Psychotria eumachioides C.M. Tayor, 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 : 170-171

Psychotria eumachioides C.M. Tayor , sp. nov. ( Fig. 1G–K ).

Holotypus: MADAGASCAR. Reg. S AVA [Prov. Antsiranana ]: Vohémar , Tsarabaria , Manakana , forêt d’Ambondrobe , 13°42'46"S 50°05'25"E, 18.V.2004, Rabehevitra et al. 1059 ( MO-5899412 !; isotype: TAN).

Psychotria eumachioides C.M. Taylor differs f rom P. rubropedicellata (Bremek.) Razafim. & B. Bremer by its stems that become yellowed and indurated with age, narrower oblanceolate leaves that lack domatia, and shorter inflorescences.

Shrubs, at least sometimes apparently deciduous, collected in flower and fruit variously at 1.5–2 m tall, branched with lateral stems usually comprising 5 to 10 nodes separated by reduced internodes; stems glabrous, weakly flattened becoming subterete, with bark often becoming yellowed or brown and thickened with age. Leaves opposite; petiole 4–28 mm, glabrous or moderately to densely puberulous or pilosulous with trichomes 0.1–0.3 mm; blade oblanceolate, 2.8–9 × 0.5–3.2 cm, at base tapered and acute, at apex broadly obtuse to rounded, drying papyraceous, on both surfaces glabrous or moderately puberulous to pilosulous with trichomes 0.1–0.3 mm; secondary veins 7 to 12 pairs, weakly looping to interconnect or reticulating near margins, without domatia, without intersecondary veins, adaxially venation plane or costa thinly impressed, secondary veins thickened, and remaining venation not evident, abaxially costa prominent, secondary veins plane to thickened, and remaining venation not evident. Stipules interpetiolar or shortly fused around stem, deciduous leaving thickened scar, ovate to triangular, 3–5 mm, abaxially glabrous or moderately pilosulous with trichomes 0.1 – 0.3 mm, adaxially sparsely pilosulous with trichomes 0.1–0.3 mm, acute to acuminate, at tip sometimes glandular or bifid with lobes 0.2–0.5 mm. Inflorescences terminal, cymose, pedunculate, sparsely to moderately pilosulous with trichomes 0.1–0.3 mm; peduncle 0.5– 1 cm; flower-bearing portion rounded-corymbiform, 1–1.5 × 1–2 cm, branched to 1 or 2 orders, c. 10- to 25-flowered; bracts reduced or usually triangular, 0.1–0.5 mm, acute; pedicels 1 – 1.5 mm. Flowers all pedicellate in umbelliform groups of 5 to 7, 5-merous; hypanthium cylindrical to ellipsoid, c. 0.8 mm, moderately pilosulous with trichomes 0.1–0.3 mm; calyx limb c. 0.8 mm, externally moderately to sparsely pilosulous with trichomes 0.1 – 0.3 mm, lobed for 1/3– 1/2 of its length, lobes ovate, acute to shortly acuminate; corolla funnelform, yellow, externally sparsely pilosulous with trichomes 0.1– 0.3 mm, tube c. 3 mm, c. 1.2 mm diam. near middle, internally glabrous except densely hirtellous in upper part of tube, lobes narrowly triangular, c. 2 mm, adaxially galeate, abaxially with rounded thickening near tip; stamens with filaments c. 1.5 mm, inserted in upper part of corolla tube, anthers c. 1.2 mm, exserted; style c. 2 mm, stigmas c. 0.8 mm, included and positioned above pubescent internal ring of corolla tube. Infructescences similar to inflorescences except sometimes displaced to pseudoaxillary by subsequent stem growth from an axillary bud, and with axes elongating and deciduous as fruits fail to develop or fall off; pedicels elongating, to 6 mm, becoming fleshy. Fruits didymous, c. 5 × 8 mm, glabrous, juicy, orange to red; pyrenes subglobose, abaxially smooth, adaxially plane; endosperm abaxially entire (i.e., not ruminate), adaxially with a few deep ruminations.

Etymology. – The species epithet refers to the similarity of this new species to some species of Eumachia , as discussed below. Eumachia has been commonly confused with Psychotria but these are not closely related ( TAYLOR et al., 2017). Eumachia differs from Psychotria in its stipules that are generally persistent and have one or two gland-tipped lobes, a lack of persistent colleters at the stipule insertion, and molecular sequences that indicate its relationships are in another tribe, Palicoureeae .

Habitat, distribution and phenology. – Psychotria eumachioides has been collected in gallery forest in subhumid or dry bioclimate zones ( CORNET, 1974), from near sea level to c. 40 m in northwestern Madagascar (Antsiranana), variously in littoral forest and on lakeshores and river banks. It has been collected with flowers in January, and with fruits in February and May .

Conservation status. – Psychotria eumachioides is known from four specimen collections representing four unique occurrences in gallery forest in subhumid or dry bioclimatic zones at 0–40 m elevation. The EOO of the species is 896 km ², within the limits for “Endangered” under IUCN Red List Criterion B1; and the AOO is 12 km ², also within the limits for “Endangered” under Criterion B2 ( IUCN, 2012). Two occurrences are within the generally well-protected Loky-Manambato PA, though there are reports of some artisanal gold mining within the protected area (C. Birkinshaw, pers. comm.). A third occurrence is near the northern boundary of, but distinctly outside, Analamerana PA, and the remaining occurrence is not in a formally recognized protected area, although the label indicates “forêt d’Ambondrobe”. Forested areas without formal protection in the vicinity of Loky-Manambato PA are subject to degradation by small-scale slash and burn agriculture and resource exploitation including logging, hunting and mining ( GOODMAN et al., 2018). The northernmost collection site outside Analamerana PA is stated to be in dry, semi-deciduous, very degraded forest, and it constitutes one “location” (sensu IUCN, 2012) with respect to the known threats. This is the northernmost location and its disappearance would significantly reduce both EOO and AOO. The two occurrences within Loky-Manambato constitute a second location, and the single occurrence at Ambondrobe Forest is a third location. With only three locations, documented degradation at the northernmost location, and general habitat degradation in unprotected sites, the Red List status of P. eumachioides is assessed as “Endangered” [EN B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)].

Notes. – Psychotria eumachioides is characterized by its stems with shortened internodes and an epidermis that often becomes yellowed and indurated with age; medium-sized oblanceolate leaves that are obtuse to rounded at the apex and lack domatia; triangular to ovate, acute, medium-sized stipules that are deciduous and leave a thickened scar; corymbiform several-flowered inflorescences that are overtopped by the leaves; flowers that are pedicellate in umbelliform cymes; developed calyx limbs; somewhat small yellow corollas; orange to red fruits borne on thickened pedicels; smooth subglobose pyrenes; and endosperm with several adaxial ruminations. The plants dry with a generally green color. The dried trichomes are mostly white, though some trichomes on old stipules turned brown. The stems do have developd internodes but these are quite short, so the growth pattern can almost be considered a brachyblast and its arrangement is accentuated by thickened petiole and stipule scars. This growth pattern may be related to the habitat of this species, which lives in relatively dry areas and is apparently deciduous. Psychotria eumachioides appears to produce flowers and new leaves together, then the fruit and stem development proceed concurrently. The few flowers seen resemble the short-styled form of distylous Psychotria species , but whether this species is distylous is not yet known. A fruiting specimen is chosen as the type because most of characters that diagnose this new species are in the fruits and seeds. Psychotria eumachioides agrees with BREMEKAMP (1963) ’s Mapouria , and keys there to either Group VI or Group V but does not fully agree with either. It agrees with Group IV in its lack of domatia, but differs in its fruits that are not blue or white at maturity; it agrees with Group V in its yellow to red fruits, but differs in its lack of domatia and entire stipules.

Psychotria eumachioides is similar to P. rubropedicellata , which has stems with regularly developed, elongated internodes, larger leaf blades 6.5–16 × 2–10 cm with pilosulous domatia and tips that are sharply obtuse to acute, stipules with two linear lobes, often larger inflorescences 2–7 cm long, and usually longer fruiting pedicels, 5–12 mm long, that become fleshy and red.

Paratypi. – MADAGASCAR. Reg. Sava [Prov. Antsiranana ]: Analamera , bank of Irodo riv. , side of Irodo village , 12°40'25"S 49°32'40"E, 41 m, 10.I.2002, De Block et al. 1172 ( BR, MO, P, TAN); Nosy Be , au bord du lac Sahaka , forêt d’Analabe , 13°04'14"S 49°53'40"E, 2.II.2003, Rabevohitra et al. 4463 ( MO, TEF); ibid. loco, 13°04'43"S 49°54'04"E, 13.V.2003, Razakamalala et al. 1272 ( MO, P, TEF).

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]