Psychotria razafimandimbisonii 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 : 180-181

Psychotria razafimandimbisonii C.M. Taylor , sp. nov. ( Fig. 3F–I ).

Holotypus: MADAGASCAR. Reg. Haute Matsiatra [Prov. Fianarantsoa ]: 2 km W de la gare Andrambovato, côté riv. Tatamaly , 21°30'07"S 47°24'06"E, 1075 m, 13.X.2000, Rakotovao & Randiantafika 1011 ( MO-04804424 !; isotype: TAN) .

Psychotria razafimandimbisonii C.M. Taylor is distinguished from P. retusa (Bremek.) A.P. Davis & Govaerts by its markedly retuse leaf blades without acarodomatia, shorter stipules, abaxially weakly ridged pyrenes, and endosperm that is ruminate on both surfaces.

Shrubs and small trees, collected in flower and fruit variously at 3–7 m tall, branched; stems glabrous, weakly flattened becoming subterete. Leaves opposite; petiole 4–42 mm, glabrous; blade obovate, 4–7 × 3–11 cm, at base acute to obtuse, at apex retuse for 1/5–1/4 of its length with sinus broadly rounded and sometimes costa terminating in an apiculate tip to 1 mm, drying papyraceous to chartaceous, glabrous on both surfaces; secondary veins 8 to 11 pairs, weakly looping to interconnect, without interescondary veins or with reticulated tertiary veins extending between some pairs of secondary veins, without domatia, adaxially costa prominulous and remaining venation plane or secondary veins sometimes thickened, abaxially costa and secondary veins prominent, loosely reticulated tertiary venation plane to prominulous, and remaining venation plane and not visible. Stipules fused around the stem for their entire length, caducous, externally glabrous, 2–4.5 mm, interpetiolarly truncate or rounded to obtusely angled, adaxially pilosulous with trichomes 0.8–1 mm, entire to bidenticulate. Inflorescences terminal, cymose, pedunculate, glabrous to moderately pilosulous with trichomes 0.1–0.3 mm, subtended by 1 reduced internode to 1 cm, at top with truncate to rounded stipules 1.5–3 mm, without leaves or with foliaceous bracts up to 2 cm; peduncles 0.6–4.5 cm; branched portion roundedcorymbiform, 2 –5.5 × 4– 9 cm, branched to 2 or 3 orders, c. 35- to 70-flowered; bracts triangular to rounded, 0.2–1 mm, aristate to bilobed or fimbriate; pedicels 0.5–2.5 mm. Flowers all pedicellate in dichasial cymes of 5 to 7, 5-merous, distylous; hypanthium ellipsoid to obconic, c. 1 mm, glabrous to puberulous; calyx limb 1–1.2 mm, glabrous, truncate to denticulate; corolla funnelform, yellow, externally glabrous, tube 4.5–5 mm, 1.2–1.5 mm diam. near middle, internally in upper part with densely pilosulous ring c. 1 mm wide with trichomes c. 0.3 mm, lobes triangular to narrowly triangular, 1.5–2 mm, at tip acute, adaxially galeate, abaxially with rounded thickening; stamens in short-styled form inserted in upper part of corolla tube, filaments c. 1 mm, anthers c. 1.5 mm, partly to fully exserted, in long-styled form filaments c. 0.3 mm, anthers c. 1 mm, included with tips positioned at top of corolla tube; style in short-styled form 2–3 mm, stigmas 0.5 –1 mm and included, in long-styled form style 5.5–6 mm, stigmas 0.8–1 mm and exserted. Infrutescences similar to inflorescences. Fruits ellipsoid to subglobose, 5–6 mm diam., glabrous, red; pyrenes 2, hemispherical, adaxially with 3–4 weak rounded longitudinal ribs; endosperm densely deeply ruminate on both surfaces.

Etymology. – This elegant, tall, distinctive new species named for one of its collectors, Dr. Sylvain Razafimandimbison, a leading specialist in Malagasy Rubiaceae and a native of Madagascar.

Habitat, distribution and phenolog y. – Psychotria razafimandimbisonii has been collected in humid evergreen forest at 400–1100 m in central eastern Madagascar (Fianarantsoa), with flowers in August through November and with fruits in April and October. This species is unusual for Psychotria in being represented by more flowering than fruiting specimens.

Conservation status. – Psychotria razafimandimbisonii is known from 13 specimen collections representing 12 unique occurrences in humid evergreen forest at 400–1100 m elevation. The EOO of the species is 322 km ², within the limits for “Endangered” under IUCN Red List Criterion B1; and the AOO is 32 km ², also within the limits for “Endangered” under Criterion B2 ( IUCN, 2012). Eleven of the collection sites are within two protected areas: Fandrina Vondrozo Forest Corridor Reserve, whose interior is well protected but parts close to villages seriously impacted by exploitation of timber and shifting cultivation (C. Birkinshaw, pers. comm.); and the well-protected Ranomafana PA. One collection is on the eastern boundary of Ranomafana PA and label information indicates the habitat is infested with invasive Psidium L.; this constitutes a single location (sensu IUCN, 2012) based on the unique threats known to occur. It is likely that the border edges of the protected area are subject to degradation by small-scale slash and burn agriculture and resource exploitation including logging, hunting and mining ( GOODMAN et al., 2018) and this location may have loss of suitable habitat. The northernmost collection is within Fandrina Vondrozo Forest Corridor Reserve, and constitutes a second location. The southernmost collection is also within Fandrina Vondrozo, along the Tatamaly River, a possible sensitive habitat due to the water resources and in a separate parcel of the Reserve, and is considered a third location. The remaining collection sites are all in the interior of Ranomafana PA and thus not subject to the threats at the first location. These constitute another location for a total of four locations with respect to known threats. Three locations are in generally well-protected areas but the fourth can be considered vulnerable for loss of habitat quality, thus the Red List status of P. razafimandimbisonii is assessed as “Endangered” [EN B1ab(iii)+2ab(iii)].

Notes. – Psychotria razafimandimbisonii is characterized by the combination of its glabrous vegetative structures; medium-sized leaves that are markedly retuse at the top and lack domatia; relatively small, broadly rounded to truncate stipules; pedunculate corymbiform inflorescences with the flowers pedicellate in dichasial groups and the peduncle borne on a reduced internode topped by a leafless node; truncate to denticulate, medium-sized calyx limbs; slender, yellow, medium-sized corollas; medium-sized ellipsoid fruits; pyrenes that are weakly ridged abaxially; and endosperm that is ruminate on both surfaces. The specimens characteristically dry brown or yellowish brown. The markedly retuse leaves are distinctive, and unusual in Rubiaceae . These are easily mistaken at first glance for leaves that are damaged by insect or physical tearing, but the complete leaves consistently have this form. The sinus is usually edged for part or all of its length by the distalmost pair of secondary veins, with no blade tissue extending out from them on the distal side. The secondary leaf veins are not markedly more closely set near the apex, so the retuse shape appears to be due to additional growth of the lamina and marginal tissue rather than to a foreshortened central portion and costa. The margins of most of the leaf blades are thinly revolute, but this may be an artifact of drying rather than a character of the living plants. The adaxial trichomes of the stipules are a little longer than the sheath, so these extend past it and can appear to be marginal cilia; whether these trichomes are covered by the stipule in life then the stipule shrinks in drying is not known. The inflorescences are distinctive in the reduced stem segment at the base of the peduncle, which is leafless but has two truncate stipules. The inflorescences are described on some labels as whitened. This new species agrees with BREMEKAMP (1963) ’s Mapouria Group VI.

Psychotria razaf imandimbisonii is similar to P. retusa (Bremek.) A.P. Davis & Govaerts , which can be separated by its leaves that are only shallowly retuse at the apex and have regularly developed domatia in the abaxial vein axils, larger stipules 9–25 mm long, abaxially smooth pyrenes, and endosperm that is ruminate only on the abaxial side. Psychotria razafimandimbisonii is also similar to P. manampamihensis (Bremek.) A.P. Davis & Govaerts , which can be separated by its generally smaller, obovate leaf blades, 5–12 × 3–6 cm, that have regularly developed domatia and are obtuse to truncate at the apex with acuminate tips 1–8 mm long, stipules that are slenderly acuminate at the top, and flowers that are subsessile or borne on shorter pedicels, up to 0.5 mm long.

Paratypi. – MADAGASCAR. Reg. Vatovavy-Fitovinanay [Prov. Fianarantsoa ]: distr. Ifadenia, Ranomafana PN , 21°15'25"S 47°25'30"E, 918 m, 24.IV.2005, Acevedo-Rodríguez & Razafindraibe 14457 ( MO, US) ; 21°02'00"S 47°18'00"E –21°25'00"S 47°37'00"E, 400–1375 m, 14.VIII.1988, Kremen 88-1 ( MO) ; 21°15'36"S 47°25'12"E, 854–915 m, 1.XI.1998, Almeda 7932 ( CAS, MO, TAN) ; 21°16'S 47°25'E, 900–1100 m, 31.X.1998, Daniel 9011 ( CAS, MO, TAN) ; 21°16'S 47°26'E, 1000–1100 m, 4.XI.1998, Daniel 9098 ( CAS, MO, TAN) ; 21°15'S 47°25'E, 1100 m, 3.XI.1997, Davis et al. 1045 ( K, MO, TAN) ; 21°15'S 47°27'E, 800–1000 m, 3–8.IX.1993, Kotozafy et al. 212 ( MO) ; ibid. loco, 900 m, 19–21.X.1993, Kotozafy & Randriamanantena 335 ( MO) ; 21°15'S 47°28'E, 950 m, 3.X.1986, Nicoll 116 ( MO) ; 7 km W of Ranomafana, Duke University Primate Center , 21°16'S 47°25'E, 1000 m, 27.X.1987, Overdorff 39 ( MO) ; 21°15'50"S 47°25'17"E, 998 m, 14.IV.2016, Razafimandimbison et al. 1381 ( MO, S, TAN) ; Vatoharanana , 40 km S Ranomafana (ville), 21°17'04"S 47°26'00"E, 1025 m, 2.X.2000, Rakotovao & Randriantafika 957 ( MO, P, TAN) .

Figures

Fig. 3. – Psychotria birkinshawiana C.M. Taylor: A. Flowering branch; B. Infrutescences with bases of two lateral stems; C. Portion of inflorescence with four flower buds; D. Corolla at anthesis; E. Cross-section of pyrene and seed. Psychotria razafimandimbisonii C.M. Taylor: F. Flowering branch; G. Stem node with bases of two petioles and one stipule; H. Portion of inflorescence with one flower from which corolla has fallen, one flower bud, and one flower at anthesis; I. Cross-section of pyrene and seed. [A: Lowry et al. 4248; B, E: Ralimanana 1209; C–D: Bernard 1675; F: Rakotovao & Randriantatafika 1011; G: Rakotovao 957; H: Daniel 9098; I: Overdorff 39]