Polyceratocarpus askhambryan-iringae A.R. Marshall & D.M. Johnson, 2016

Marshall, Andrew R., Couvreur, Thomas L. P., Summers, Abigail L., Deere, Nicolas J., Luke, W. R. Quentin, Ndangalasi, Henry J., Sparrow, Sue & Johnson, David M., 2016, A new species in the tree genus Polyceratocarpus (Annonaceae) from the Udzungwa Mountains of Tanzania, PhytoKeys 63, pp. 63-76 : 64-67

Polyceratocarpus askhambryan-iringae A.R. Marshall & D.M. Johnson sp. nov. Figs 1, 2, 3

Diagnosis.

This species may be distinguished from other species of Polyceratocarpus by the combination of glabrous non-glaucous leaves with finely reticulate to weakly scalariform tertiary venation, pedicels 15-22 mm long, broadly ovoid buds, chartaceous petals 10-17 mm long, 5 to 18 carpels/monocarps, and relatively large torulose monocarps.

Type.

Marshall 2117 (holotype K; isotypes DSM, MO, NHT), Tanzania, Iringa Region: Ndundulu Forest, Kilombero Nature Reserve, Udzungwa Mountains , 07°48'S, 36°31'E (WGS84), 1490 m, 30 May 2011 .

Description.

Monopodial tree to 20 m tall, 4.0-25.4 cm diam.; bark smooth, sparsely lenticellate, often with weak horizontal striations and pits on large trees, grey-brown; branches spirally arranged on trunk, branching from half to two fifths of the height of the main stem, perpendicular but sinuous and drooping slightly; twigs longitudinally rugulose, inconsistently marked with small but prominent lenticels, glabrous, brown. Leaves: petiole 4-9 mm long, 1.6-3.3 mm thick, roughened, black, glabrous; lamina narrowly to broadly elliptic-oblong to oblanceolate, or rarely obovate, (5.0-)9.0-25.7 by (3.7-)4.9-8.6(-11.6) cm, chartaceous to coriaceous, greenish gray in sicco, glabrous on both surfaces, base rounded and minutely subcordate, apex acuminate with the acumen 12-20 mm long or occasionally obtuse, midvein plane to slightly impressed above, raised below, secondary veins 9 to 17 per side, diverging at 45-60° from midrib, eucamptodromous to weakly brochidodromous, slightly raised to slightly impressed above, raised below, tertiary veins finely reticulate to somewhat scalariform, indistinct to slightly raised above, raised and conspicuous below. Inflorescences 1- or 2-flowered, axillary or occasionally ramiflorous, forming tubercles on leafless growth; pedicels 15-29 mm long 1-3 mm diam., finely appressed-puberulent, bearing a bract 0.8-1 mm long 1/4-2/5 of the distance above pedicel base. Flowers bisexual or staminate, buds broadly ovoid; sepals 3, valvate, crescent-shaped, 2-3.5 mm long, partially connate at the base so that as corolla expands the calyx becomes discoid to triangular with diameter of 7-8 mm, appressed-puberulent abaxially; petals in two whorls of 3, pale yellow in vivo; outer petals occasionally tinged pink on abaxial surface in vivo, valvate, spreading horizontally and recurving at anthesis, narrowly elliptic to elliptic or oblong-elliptic, 10-16 mm long by (5-)8-11 mm wide, coriaceous, apex obtuse, sparsely pubescent adaxially, ferruginous appressed-puberulent but becoming glabrate and verrucose abaxially; inner petals sometimes with a pale brownish-yellow median stripe abaxially, valvate, erect at anthesis with the apices recurved, narrowly elliptic-lanceolate, elliptic, or elliptic-oblanceolate, 11-17 mm long × 5-7 mm wide, coriaceous, external surface marked by a broad flattened ridge that narrows from base to apex, glabrous adaxially, appressed-puberulent with trichomes densest along ridge and at apex abaxially, verrucose on both surfaces, apex acute; stamens ca. 200, 2.0-2.8 mm long, clavate, apex of connective obliquely truncate, pale brown with orange apex, glabrous?; carpels 5 to 18, oblong, 2.9-4.0(-6.0) mm long by 0.9-1.1(-2.3) mm wide, densely pale brown/ferruginous-puberulous; stigma bilobed, capitate, 1 mm in diam., glabrous, ovules ca. 10, uniseriate; torus subglobose to broadly pyriform to oblate, 4.4-4.9 mm long by 2.6-5.4 mm diam., 3-8 mm diam. at base. Pedicel of fruit 20-44 mm long by 3-7 mm diam., weakly longitudinally rugulose, glabrate; torus of fruit ellipsoid to broadly pyriform, 7-15 mm diam. × 8-12 mm long, grey-brown. Monocarps up to 18 per fruit, green (rarely with orange or vinaceous tinge) in vivo, dark brown when dried, weakly (to strongly) recurved-falciform, (1.9) 6.0-8.6 cm by 0.7-2.2 cm, torulose, minutely verrucose, glabrate or with a few scattered hairs, base sub-sessile or short-stipitate, stipe 1-11 mm long, 2-6 mm thick, apex rounded or sometimes short-beaked. Seeds 1-15 per monocarp, 15 mm long by 13 mm wide by 10 mm thick, arranged in a single [or two irregular?] rows, flattened-ellipsoid, pitted, with spiniform ruminations (fig. 3) and raphe/antiraphe sunken in a circumferential groove.

Distribution.

Polyceratocarpus askhambryan-iringae is endemic to the Udzungwa Mountains of Tanzania. It is known from Mwanihana Forest in the Udzungwa Mountains National Park, Ndundulu Forest in the Kilombero Nature Reserve, and the Uzungwa Scarp Forest Reserve (Fig. 1).

Habitat and ecology.

Inhabits montane forest on brown sandy loam soils (pH range 4-5 measured in Ndundulu Forest). Mean annual rainfall of collection localities approximately 1500-2000 mm/yr (Marshall, Ndangalasi, unpubl. data). Thirty-eight mature individuals were found mostly on slopes or ridge-tops at elevations 1090-1540m. Mature flowers were collected in May, November, and December, fruits in February and May-October.

Associated taxa recorded with Polyceratocarpus askhambryan-iringae include the following: (1) Ndundulu Forest: Allanblackia ulugurensis Engl., Alsodeiopsis schumannii Engl.; Anisotes pubinervius (T.Anderson) Heine, Anthocleista grandiflora Gilg, Beilschmiedia kweo (Mildbr.) Robyns & Wilczek, Bertiera pauloi Verdc., Cassipourea gummiflua Tul.; Cassipourea malosana Alston; Chlorophytum brachystachyum Baker, Cleistanthus polystachyus Hook.f. ex Planch., Clerodendrum cephalanthum Oliv., Coffea sp., Cola greenwayi Brenan, Cola stelechantha Brenan; Craterispermum longipedunculatum Verdc.; Diospyros abyssinica (Hiern) F.White, Drypetes gerrardii Hutch.; Englerina sp. nov.; Garcinia buchananii Baker; Garcinia volkensii Engl.; Grewia mildbraedii Burret; Justicia rodgersii Vollesen; Lasiodiscus usambarensis Engl.; Maytenus undata (Thunb.) Blakelock; Monodora globiflora Couvreur; Monanthotaxis schweinfurthii Engl. & Diels; Myrianthus holstii Engl., Ocotea usambarensis Engl.; Ochna holstii Engl.; Parinari excelsa Sabine, Peddiea fischeri Engl., Pavetta nitidissima Bridson, Plectranthus leptophyllus (Baker) A.J.Paton, Rinorea angustifolia Baill. subsp. ardisiiflora (Oliv.) Grey-Wilson; Rinorea sp.; Rytigynia lichenoxenos (K.Schum.) Robyns subsp. glabrituba Verdc.; Sclerochiton obtusisepalus C.B.Clarke; Solanecio epidendricus (Mattf.) C.Jeffrey; Strombosia scheffleri Engl.; Strychnos mellodora S.Moore; Strychnos mitis S.Moore; Strychnos sp. nov; Syzygium guineense DC.; Tabernaemontana stapfiana Britten; Tarenna pavettoides (Harv.) Sim; Thalictrum rhynchocarpum Quart.-Dill. & A.Rich.; Uvariopsis lovettiana Couvreur & Q.Luke; Vepris stolzii I.Verd.; Vernonia calvoana Engl. subsp. leucocalyx (O.Hoffm.) C.Jeffrey; Vernonia luhomeroensis Q.Luke & Beentje; Vernonia sp. nr. pteropoda Oliv. & Hiern; Warneckea sp. nov.; Xymalos monospora Baill.; Zanthoxylum paracanthum (Mildbr.) Kokwaro; Zehneria sp. nr. oligosperma C.Jeffrey. (2) Uzungwa Scarp Forest Reserve: Cassipourea gummiflua Tul; Cleistanthus polystachyus Hook.f. ex Planch.; Craterispermum longipedunculatum Verdc.; Diospyros uzungwaensis Frim.- Møll. & H.J.Ndangalasi; Drypetes gerrardii Hutch.; Lasiodiscus usambarensis Engl.; Psychotria megalopus Verdc.; Tabernaemontana stapfiana Britten; Tarenna uzungwaensis Bridson. (3) Mwanihana: Acalypha psilostachya Hochst. ex A.Rich. var. psilostachya ; Anisotes pubinervius (T.Anderson) Heine; Caloncoba welwitschii Gilg; Chrysophyllum gorungosanum Engl.; Coffea mufindiensis Hutch. ex Bridson subsp. mufindiensis ; Dorstenia sp. aff tenuiradiata Mildbr.; Isoglossa lactea Lindau ex Engl. subsp. lactea ; Isolona linearis Couvreur; Newtonia buchananii (Baker) G.C.C.Gilbert & Boutique; Ochna holstii Engl.; Parinari excelsa Sabine; Phyllopentas ulugurica (Verdc.) Kårehed & B. Bremer; Kedrostis sp.; Polystachya sp aff. canaliculata Summerh.; Raphidiocystis chrysocoma (Schumach.) C.Jeffrey; Selaginella kraussiana (Kunze) A.Braun; Stellaria mannii Hook.f.; Tricalysia aciculiflora Robbr.; Uvariopsis lovettiana Couvreur & Q.Luke; Vepris nobilis (Delile) Mziray; Zanthoxylum paracanthum (Mildbr.) Kokwaro.

Additional specimens examined.

TANZANIA. Iringa Region, Kilolo District: east Udzungwa National Park, forest south of Mwanihana hill c. 2 km S of last camping site of Mwanihana trail, 1400 m, 07°48'S, 36°49'E, Couvreur 101 (DSM, OWU, WAG); Mwanihana Forest above Sanje village , 1220 m, no grid reference, Lovett 222 (K); Udzungwa Mountains National Park , 1200 m, 07°48'S, 36°49'E, Luke 7738 (EA, K); Udzungwa Mountains National Park , 1440 m, 07°42'S, 36°52'E, Luke 11279 (EA, NHT, MO, K); Ndundulu FR, Camp 589-Camp 590, 07°47'S, 36°29'E, 1440 m, Luke et al. 10366 (MO); Kilombero Nature Reserve , Ndundulu Forest , 1540 m, 07°48'S, 36°31'E (WGS84), Marshall 2036, 2070, (NHT, MO, K); Uzungwa Scarp Forest Reserve , Uluti, 1534 m, 08°14'S, 36°01'E, Ndangalasi HJN 392 (DSM, OWU); Uzungwa Scarp Forest Reserve , Ilutila, 1709 m, 08°13'S, 36°01'E, Ndangalasi 393 (DSM, OWU); Udzungwa, Kilombero FR, W of Ruaha River, 1700 m, Rogers & Hall 2300 (K); Mwanihana Forest above Sanje village , 1400 m, 07°50'S, 36°49'E, Thomas 3656 (MO); Mwanihana Forest above Sanje village , 1400 m, 07°50'S, 36°49'E, Thomas 3698 (MO, WAG) . Morogoro Region, Kilombero District: Sonjo-Mwanihana trail, 1090 m, 07°48'S, 36°51'E, Luke 5051 (EA, K) .

An additional specimen from Iringa Region (Nyambanitu Forest, Ede 65, K), may also represent this species but bears only an old fruit pedicel lacking monocarps. Further potential Polyceratocarpus collections from Iringa Region (Lulanda Forest Reserve: Gereau 2651, 2664, 2665, MO; Lovett 2256, MO, WAG; Luke & Luke 12779, EA & K), were identified as neither Polyceratocarpus askhambryan-iringae nor Polyceratocarpus scheffleri , while another from Morogoro Region was not considered to be from this genus at all ( Kimboza Forest Reserve : Parry 1816, TFD; cited Verdcourt 1971) .

Additional field notes.

Slash dry, slightly stringy, pale yellow (to pale peach), occasionally streaked yellow-brown, dark brown at outer edge formed by the colour of the inner bark, potpourri aroma. Leaf lamina dark green above, mid-green with greyish tinge below, turning greenish-grey when dried, new flush pinkish; petiole initially pale green in vivo, becoming roughened grey-brown with age; midrib yellow-green above and below in vivo. Flower buds broadly ovoid, green or pale brown-yellow with occasional pink tinge at apex in vivo; sepals yellowish-green in vivo.

Etymology.

This new species of Polyceratocarpus was named by Askham Bryan College and Iringa International School as part of a rainforest education program.

Conservation status.

Our IUCN Red List assessment for Polyceratocarpus askhambryan-iringae was based on "area of occupancy" (AOO), "extent of occurrence" (EOO; IUCN 2012) and the level of threat. The 38 observed mature Polyceratocarpus askhambryan-iringae stems were found at four collection localities, with only 112 km between the most distant individuals. The four collection localities represented three different levels of governmental protection, including Forest Reserve (Uzungwa Scarp), Nature Reserve (Kilombero, KNR; and also Uzungwa Scarp proposed status) and National Park (Udzungwa Mountains; UMNP), with only UMNP having the maximum level of protection under Tanzanian law (IUCN category II; Dudley 2008). At the time of survey, the greatest threat to Polyceratocarpus askhambryan-iringae was widespread timber-felling observed in Uzungwa Scarp Forest Reserve. Conversely, threats to Polyceratocarpus askhambryan-iringae in KNR and UMNP were much lower, both comprising only very occasional removal of pole-sized trees by villagers, and potential damage from an increasing elephant population ( Marshall et al. 2012). KNR was further threatened by a lack of formal ranger patrols and rapid population expansion in the nearest villages. Given that the sources of threat were closely associated with the three protected areas, for the purpose of Red List assessment we considered three rather than four threat-defined “locations” ( IUCN 2012). In calculating AOO, we used 10 km2 grid cells so that the projected area was not extrapolated far beyond the expected habitat tolerance of the species. We estimated an AOO of 300 km2 and an EOO of 1,410 km2, with EOO, AOO, habitat quality and the number of mature individuals, all presumed declining as a result of timber-felling in USFR. Given this continuing decline, plus an EOO of less than 5,000 km2, an AOO of less than 500 km2, and a population at no more than five locations, the species qualified firmly as endangered on the IUCN Red List ( IUCN 2012), EN B1ab(i,ii,iii,v)+2ab(i,ii,iii,v). Within the Udzungwa Mountains, closed-canopy forest was not extensive at elevations suitable for Polyceratocarpus askhambryan-iringae , and hence we expect that future expeditions will not expand the AOO or EOO of Polyceratocarpus askhambryan-iringae above the IUCN endangered threshold. However, the Rubeho and Mahenge mountain blocs adjacent to Udzungwa were more poorly known, and may contain suitable habitat in which this species might also be found.