Psychotria notopleuroides 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 : 176-178

Psychotria notopleuroides C.M. Taylor , sp. nov. ( Fig. 1L–N ).

Holotypus: MADAGASCAR. Reg. SAVA [Prov. Antsiranana ]: Masoala Peninsula , 3 km SW of “Tamany Fred”, watershed of Anaovandrano riv ., 15°45'30"S 50°11'45"E, 50 m, 15.X.1996, Schatz et al. 3666 ( MO-4848658 !; isotype: TAN) .

Psychotria notopleuroides C.M. Taylor differs from other species of this genus in Madagascar by the combination of its prostrate habit, elliptic leaves that are apically obtuse to truncate and dark green adaxially, shortly cymose inflorescences with well developed peduncles, four-merous flowers, fruits that are red at maturity, and seeds with the endosperm entire except for a T-shaped adaxial intrusion.

Subshrubs or fleshy herb s, little-branched, with main stems prostrate and rooting, producing ascending, leaf-bearing, erect stems up to 0.3 m tall; stems glabrous or when young densely hirtellous or pilosulous with trichomes 0.2–0.5 mm, flattened becoming subterete. Leaves opposite; petiole 6–31 mm, densely tomentulose to pilosulous or hirtellous with trichomes 0.2– 0.5 mm; blade elliptic to obovate, 5– 12 × 2.3 – 6.6 cm, drying papyraceous to chartaceous, adaxially glabrous, abaxially densely hirtellous on veins and sparsely hirtellous on lamina with trichomes 0.1–0.5 mm; secondary veins 5 to 12 pairs, looping broadly to interconnect near margins, without intersecondary veins, without domatia, adaxially venation plane or costa prominulous, abaxially costa and secondary veins prominent and remaining venation not visible. Stipules interpetiolar or shortly united around stem, caducous, abaxially hirtellous with trichomes 0.2–0.5 mm, ovate, 3–6 mm, adaxially glabrous, bilobed, lobes linear, 1–2 mm, glandular at tip. Inflorescence terminal, shortly cymose, pedunculate, sparsely to densely hirtellous with trichomes 0.3–1 mm, green; peduncle 3–5.5 cm; branched portion corymbiform, 0.6–2 × 1–2 cm, 10- to 30-flowered, branched to 1 or 2 orders; bracts narrowly triangular, 0.5–2 mm, acute, at tip glandular; pedicels 0.1 – 1.5 mm. Flowers subsessile to pedicellate with both arrangements mixed in cymose to umbelliform groups of 3 to 9, 4-merous; hypanthium obconic to cylindrical, c. 1 mm, glabrous or puberulous with trichomes 0.2–0.3 mm; calyx limb 1–1.2 mm, externally glabrous, shallowly lobed, lobes broadly triangular, obtuse, marginally with 2 or 3 glands on each lobe; corolla tubular to funnelform, white, externally glabrous, tube c. 3 mm, 1.2– 2 mm diam. near middle, internally in upper part and throat with dense ring c. 1 mm wide of pilosulous trichomes 0.3–0.5 mm, lobes ligulate, 1.2–1.5 mm, obtuse to rounded, adaxially plane or with minute galeate projection, abaxially smooth; stamens inserted in upper part of corolla tube, filaments c. 0.5 mm, anthers c. 0.8 mm, included or partially exserted; style c. 3.5 mm, stigmas c. 0.3 mm, exserted. Infructescences similar to inflorescences, except becoming displaced to pseudaxillary by stem growth from one axillary bud. Fruits ellipsoid, c. 6 × 5 mm, glabrous, red, apparently fleshy; pyrenes 2, hemispherical, adaxially plane, abaxially with 4–5 rounded longitudinal ridges; endosperm entire abaxially, adaxially with 1 medial, longitudinal, T-shaped intrusion.

Etymology. – This new species resembles several species of the neotropical genus Notopleura (Benth.) Bremek. , and the species epithet refers to this similarity. Notopleura has been commonly confused with Neotropical species of Psychotria but these genera are not closely related ( RAZAFIMANDIMBISON et al., 2014). Terrestrial species of Notopleura differ from Psychotria in their consistently pseudoaxillary inflorescences, stipules with well developed glands on the margins and/or a medial appendage, lack of persistent colleters at the stipule insertion, and molecular sequences that indicate their relationships are in another tribe, Palicoureeae .

Habitat, distribution and phenology. – Psychotria notopleuroides has been collected in perhumid evergreen forest at 0–200 m on the Masoala Peninsula in eastern Madagascar (Antsiranana, Toamasina), with flowers in October and November and with fruits in June and September .

Conservation status. – Psychotria notopleuroides is known from four specimen collections representing four unique occurrences in perhumid evergreen forest at 0–200 m elevation. The EOO of the species is 69 km ², within the limits for “Critically Endangered” under IUCN Red List Criterion B1; and the AOO is 16 km ², within the limits for “Endangered” under Criterion B2 ( IUCN, 2012). Three occurrences are within the Masoala PA. Two of these occurrences are in the Anaovandrano river watershed and may be particularly sensitive to disturbances. The interior of Masoala PA is well protected but parts close to villages are impacted by exploitation of timber and, to a lesser extent, shifting cultivation (C. Birkinshaw, pers. comm.). A fourth occurrence is the westernmost point, at Ambanizana, and is approximately 800 m outside Masoala PA. Forested areas without formal protection in the vicinity of Masoala 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 westernmost collection site is along the Androka River and it constitutes one location (sensu IUCN, 2012) with respect to the known threats. This location’s disappearance would reduce EOO, AOO, the number of locations, and the number of mature individuals. The two easternmost occurrences, within the Anaovandrano River watershed, constitute a second location with regard to known threats, and the remaining occurrence, within Masoala PA, south of the unprotected occurrence, is a third location. With three locations, the sensitive nature of watershed habitats at two of the locations, and given general habitat degradation in unprotected sites, the Red List status of P. notopleuroides is assessed as “Endangered” [EN B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)].

Notes. – Psychotria notopleuroides is characterized by its unusual prostrate habit, triangular caducous stipules, mediumsized to rather small leaves that are obtuse to usually rounded or truncate at the apex, shortly cymose inflorescences that are initially terminal but quickly displaced to pseudoaxillary by subsquent growth from an axillary bud, somewhat small four-merous corollas, medium-sized red fruits, pyrenes that are shallowly ridged abaxially, and endosperm that lacks ruminations except for a well developed, medial, T-shaped intrusion on the adaxial face. The specimens dry with a brown or reddish brown color, and the dried trichomes are dark reddish brown. The prostrate stems root along their length, and produce new stems sympodially. The leaves appear to be similar to those of some other Rubiaceae found in dark humid understory, with the epidermis composed of relatively large cells, the upper surface dark velvety green in life, and the lower surface light-colored and perhaps silvery. The collection data of one specimen (Zjhra & Hutcheon 378) note that the leaves are brittle. Most of the leaves on the dried specimens have revolute margins, but it is not clear if this is a character found in life or an artifact of drying. The corolla lobes of P. notopleuroides are distinctive in being rounded at the tips, similarly to the leaves, rather than acute as in most species of this genus. Two flowering collections have been seen, and both agree with the long-styled form of distylous Psychotria species ; whether this new species is distylous cannot yet be determined. This new species is not similar to any other Psychotria known from Madagascar.

The pyrenes of Psychotria notopleuroides have the form BREMEKAMP (1963) used to diagnose Apomuria . All the Malagasy species of that group, however, differ from this new species in their erect shrub habit and five- or six-merous flowers. At first glance Psychotria notopleuroides is similar in aspect to the Rubiaceae genera Geophila D. Don and Puffia Razafim. & B. Bremer , but both of those differ in their cordiform leaves, subcapitate inflorescences, and seeds with endosperm that lacks any rumination or intrusions. Psychotria notopleuroides is also similar to P. decumbens (Bremek.) A.P. Davis & Govaerts , which is not well known but can be separated by its hirtellous bilobed stipules and oblanceolate leaves with acute to deltate tips that appear, based on herbarium specimens, to be similarly colored on both surfaces. The number of P. decumbens ’s corolla lobes was not described and cannot be discerned from the on-line type images. Bremekamp classified P. decumbens in Mapouria , which was diagnosed by its seed with the endosperm ruminate to some degree, but he did not actually see its seeds so this character has also not been confirmed.

Paratypi. – MADAGASCAR. Reg. Sava [Prov. Antsiranana ]: Antalaha-CR Vinanivao , CAP Masoala Grand Parc , 15°44'S 50°10'E, 50 m, 15.IX.2003, Wohlhauser et al. 503 ( G, MO, NEU). Reg. Analanjirofo [Prov. Toamasina ]: Masoala Peninsula , Tampolo , 15°41'52"S 49°57'56"E, 22.X.2001, Labat & Andrianjafy 3377 ( BR, G, K, MO, TAN, TEF); Ambanizana , along Androka River south of MBG house , 15°39'30"S 49°57'30"E, 0 m, VI.1993, Zjhra & Hutcheon 378 ( MO) .

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]