Psychotria mutabilis 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 : 174-176

Psychotria mutabilis C.M. Taylor , sp. nov. ( Fig. 6 ).

Holotypus: MADAGASCAR. Reg. Atsinanana [Prov. Toamasina ]: Vatomandry , Ambalabe, Ambinanindrano II , Vohibe forest , mountain ridge NW of MBG Camp , 19°08'35"S 48°34'29"E, 720 m, 23.XI.2013, Randrianasolo et al. 1506 ( MO-6877034 !; isotype: G [ G00341932 ]!, P, TAN) .

Psychotria mutabilis C.M. Taylor is distinguished from P. rufovillosa (Bremek.) A.P. Davis & Govaerts by its proportionally broader leaf blades, inflorescences that are initially subsessile and subcapitate then expand tardily, six-merous flowers, corollas with longer lobes, 3 mm long, and larger fruits.

Shrubs and small trees, collected in flower and fruit variously at 2–6 m tall, branched; stems weakly flattened to subquadrangular, becoming terete with age, densely hirtellous to hirsute with trichomes 1–2 mm. Leaves opposite; petiole 10–80 mm, densely hirtellous to hirsute with trichomes 1–2 mm; blade obovate to elliptic or broadly elliptic, 6–20.5 × 2.5–12.2 cm, at base cuneate to obtuse, at apex obtuse to broadly rounded and shortly acuminate with tip 1–5 mm, drying chartaceous, adaxially glabrous, abaxially moderately to densely hirtellous, pilosulous, or hirsute on veins and lamina with trichomes 1–2 mm; secondary veins 9 to 14 pairs, reticulating sparsely to extensively near margins or sometimes looping weakly to interconnect near margins, without intersecondary veins or more often with 1 weak intersecondary vein present between pairs of secondary veins, sometimes with a distinct dense tuft of pubescence in abaxial axils of secondary veins, adaxially venation plane or costa thickened, abaxially costa and secondary veins prominent, intersecondary and loosely reticulated tertiary and quaternary venation plane to prominent, and remaining venation plane. Stipules interpetiolar, caducous, on both surfaces moderately to densely pilosulous or hirtellous with trichomes c. 1 mm, ovate, 12–21 mm, abaxially with triangular central portion bounded by low rounded ridges, 2-lobed, lobes linear to ligulate, 2–4 mm, acute, adaxially with dense row of persistent pilose trichomes 1–1.5 mm borne on stem at base of stipule. Inflorescences terminal, subcapitate, subsessile; flowering head subglobose, 2–3 cm diam., c. 45- to 60-flowered; bracts narrowly triangular, 1–3 mm, acute. Flowers all subsessile in glomerules of 3 to 7, surrounded at base by sericeous to pilose trichomes 1–2 mm, 5- or 6-merous; hypanthium obconic, c. 2 mm, densely pilose to hirtellous with trichomes 1–2 mm; calyx limb 2–3 mm, glabrous or sparsely hirtellous with trichomes c. 0.5 mm, truncate to shallowly broadly lobed, lobes up to 0.5 mm, marginally densely pilosulous with trichomes 0.5–0.8 mm; corolla tubular-funnelform, yellow, externally sparsely strigillose with trichomes 0.1–0.3 mm, tube cylindrical to funnelform, 2.5–3.5 mm, 2–2.5 mm diam. near middle, internally glabrous except with densely pilosulous ring c. 1 mm wide in upper part, lobes ligulate, 2.5–3 mm, fleshy, adaxially shortly galeate, abaxially with rounded thickening 0.5–1 mm; stamens inserted in upper part of corolla tube, filaments c. 0.3 mm, anthers c. 0.8 mm, included; style 5–6 mm, stigmas 0.5– 0.8 mm, exserted. Infrutescences becoming lax, cymose, pedunculate; peduncle 1–4.5 cm; branched portion broadly pyramidal to corymbiform, 1.5–2 × 4.5–7 cm, branched to 1 to 3 orders. Fruits sessile or with stipe up to 2 mm, subglobose to ellipsoid, 10–11 mm diam., sparsely to moderately pubescent with pilose to hirtellous trichomes c. 1 mm, dark green becoming orange or or red, fleshy; pyrenes 2, hemispherical, adaxially plane, abaxially smooth; endosperm densely and deeply ruminate on both surfaces.

Etymology. – The specific epithet refers to the extenstive morphological change from the inflorescence to the infructescence.

Habitat, distribution and phenology. – Psychotria mutabilis has been collected in perhumid evergreen forest at 640–1100 m in east-central Madagascar (Fianarantsoa, Toamasina), with flowers in November and with well-developed fruits in April, May , and November .

Conservation status. – Psychotria mutabilis is known from 12 specimen collections representing 12 unique occurrences in perhumid evergreen forest at 640–1100 m elevation. The EOO of the species is 19,610 km ², within the limits for “Vulnerable” under IUCN Red List Criterion B1; and the AOO is 40 km ², within the limits for “Endangered” under Criterion B2 ( IUCN, 2012). Six of the collection sites are within five protected areas: Analamazoatra PA and Mantadia PA, both with a good level of protection; Makira PA and Ankeniheny-Zahamena Corridor PA (two occurrences), both with the interior of reserve well protected but parts close to villages seriously impacted by exploitation of timber and, to a lesser extent, shifting cultivation; and Ranomafana PA, with a good level of protection. The other six collection sites are in unprotected areas adjacent to but outside Analamazoatra, Ankaniheny-Zahamena, and Ranomafana. Forested areas without formal protection in the vicinity of these protected areas are subject to degradation by small-scale slash and burn agriculture and fire to create habitat for cattle farming as well as resource exploitation including logging, hunting and mining ( GOODMAN et al., 2018). The five protected areas with one or more collection sites constitute one “location” (sensu IUCN, 2012) each. The remaining six collection sites can be considered as four distinct locations, based on geographic clustering with respect to the scale of the known threats, giving a total of nine locations. Four collection sites in or near Mantadia PA are in close proximity to an active graphite mine and a reduction in habitat, locations, and mature individuals can be inferred. The four unprotected locations are subject to general habitat degradation and at least one of the protected areas is in close proximity to on-going mining operation, causing a decline in AOO, extent and/or quality of habitat, and number of mature individuals. Thus, the Red List status of P. mutabilis is assessed as “Vulnerable” [VU B1ab(ii,iii,iv,v)+2ab(ii,iii,iv,v)].

Notes. – Psychotria mutabilis is characterized by its dense hirtellous pubescence on both vegetative and reproductive structures; medium-sized leaf blades that are mostly obtuse at the tip; well developed interpetiolar stipules with two acute lobes; inflorescences that are initially subsessile, subcapitate, and globose then expand markedly in fruit; subsessile six-merous flowers; rather well developed tubular calyx limbs with rounded, short, densely pubescent lobes; medium-sized yellow corollas; lax, branched inflorescences with well developed peduncles and axes; somewhat large red fruits; and endosperm that is ruminate on both surfaces. The plants dry with a brown or reddish brown color, and the dried trichomes are dark reddish brown or reddened. The upper surfaces of the leaf blades seen are unusual in being completely glabrous, rather than having sparse pubescence at least on the principal veins as in other Psychotria species with dense pubescence. This species apparently lacks crypt-type domatia, but the dense pubescence of the abaxial vein axils may function as acarodomatia. The few flowers seen agree with the long-styled form of distylous Psychotria species , but whether this species is distylous cannot be confirmed. The change in form between the subcapitate, subsessile inflorescence and the lax infructescences is notable, but both of these structures are borne on the same stem of McPherson & van der Werff 16495 so they clearly belong to the same species. This species agrees with BREMEKAMP (1963) ’s Mapouria Group VI.

Psychotria mutabilis is similar to P. rufovillosa , which differs in its elliptic to narrowly elliptic leaf blades 3.5 –7 cm wide, inflorescences that are branched before flowering commences and borne on developed peduncles, five-merous flowers, corollas with shorter lobes c. 2 mm long, and smaller fruits 5–6 mm in diameter.

Paratypi. – MADAGASCAR. Reg. Vatovavy-Fitovinany [Prov. Fianarantsoa ]: Ifadenia , PN Ranomafana , 21°15'31"S 47 °25'16"E, 974 m, 11.VI.1996, Birkinshaw 264 ( MO, TAN); ibid. loco, 21°18'00"S 47°38'30"E, 29.V.2004, Rakotonasolo & Zachary 805 ( K, MO, TAN). Reg. AlaotraMangoro [Prov. Toamasina ]: PN Mantadia , 18°47 '58"S 48°25'43"E, 19.IV.2010, De Block et al. 2528 ( BR, K, MO, TAN); ibid loco, 18°47'47"S 48°25'32"E, 1100 m, 7.IV.2004, Maurin 145 ( K, MO, TAN); ibid. loco, 18°55'S 48°25'E, 900 m, 2.XI.1994, McPherson & van der Werf 16468 ( K, MO); ibid. loco, 18°48'03"S 48°25'41"E, 965 m, 26.V.2011, Razakamalala 6574 ( MO, S, TAN); Bekalakody, corridor forestier Analamay Mantadia , 18°45'37"S 48°25'37"E, 943 m, 28.IV.2012, Razafindrahaja & Antilahimena 242 ( MO, P, TAN); Atsinanana, Didy à Brickaville , [18°29'S 48°48'E], 1954, Cours 4904 ( MO, P); Makira PA , 15°23'53"S 49°27'05"E, 750 m, 14.V.2007, Davis 4505 ( K, MO, TAN); NW of Foara Habitation , 19°08'58"S 48°35'39"E, 640 m, 14.III.2005, Randrianasolo et al. 1007 ( MO, TAN); Périnet-Analamazaotra , [18°56'S 48°26'E], 22.I.1968, Service Forestier 28141 ( MO, P) .

Figures

Fig. 6. – Psychotria mutabilis C.M. Taylor. A. Flowering stem; B. Corolla, external view; C. Basal portion of flower: hypanthium, calyx,