Perrottetia taronensis B.M.Barthol. & K.Armstr., 2021

Bartholomew, Bruce, Armstrong, Kate E., Li, Rong & Fritsch, Peter W., 2021, Perrottetia taronensis B. M. Barthol. & K. Armstr., sp. nov. (Dipentodontaceae), a new species from northwestern Yunnan Province, China and northern Kachin State, Myanmar and a re-examination of the Asian and Australasian taxa of Perrottetia, PhytoKeys 183, pp. 67-76 : 67

Perrottetia taronensis B.M.Barthol. & K.Armstr. sp. nov.

Figures 1 , 2 , 3

Type.

China. Yunnan Province: Gongshan Xian 贡山县, Dulongjiang Xiang 独龙江乡, Maku Cun 马库村 [Taron River], NW facing 30-60° slope, vicinity of Nangza (Pinyin: Laza) 腊咱, W side of the Dulong Jiang valley , ca. 1.3 direct km S of Maku and ca. 3.8 direct km NE of the Myanmar border, 1970 m, 27.6747°N, 98.3015°E, 18 August 2006, Gaoligong Shan Biodiversity Survey 32394 (holotype: KUN! accession 0856752 barcode 1418097; isotypes: BRIT! barcode BRIT478072, CAS! accession 1090250 barcode 346898, E! barcode E01016879, GH! barcode 00288213) .

Diagnosis.

Perrottetia taronensis is similar morphologically to P. alpestris s.s. (see Discussion) from which it differs by having much more compact and shorter inflorescences which are sparsely golden tan-tomentose rather than sparsely reddish brown-tomentose, a shorter stipe, leaf margins that are sharply serrate rather than bluntly serrate, and larger fruit when mature.

Description.

Shrubs or small trees 1.5-6.0 m tall, often sprawling, likely dioecious, deciduous. Stems reddish brown, pale brown-tomentose when young, glabrescent. Stipules reddish brown-tomentose, triangular, ca. 1.5 × 0.5 mm, often cauducous, apex long-acuminate. Petioles 0.5-1.0 cm. Leaves alternate, mostly glabrescent; leaf buds and young leaves dactylose (Figs 1B , 3 ), reddish brown-tomentose (Fig. 3 ), persistent as small naked buds over winter; mature leaf blades chartaceous, mostly glabrescent, sometimes with domatia abaxially in axils of main lateral veins, when fresh abaxially pale pinkish greenish (Fig. 2A ) and adaxially dark green (Fig. 2B ), when dry abaxially pale brownish green and adaxially dark green, narrowly ovate to elliptic, 10-15 × 3.0-7.5 cm, abaxially aveolate, sometimes sparsely tomentose on veins, midvein prominent, secondary and tertiary veins prominent, adaxially rugose, glabrous, midvein slightly prominent, secondary and tertiary veins slightly depressed, base rounded to broadly cuneate and slightly asymmetric with margin narrowly recurrent onto petiole, margins sharply serrate with 0.5-0.8 mm forward-facing sharply pointed corniculate teeth 0.2-0.3 mm wide at their base, apex narrowly acuminate and often slightly curved. Inflorescences axillary, paniculate thyrses, 1-2 cm, ca. 25-40-flowered but much reduced in number in fruit, sparsely golden tan-tomentose, with ca. 1.2 × 0.5 mm narrowly triangular acuminate bracts, basal portion of inflorescences before the first branch 1-2 mm. Flowers and fruit with a basally articulate 0.5-0.6 mm stipe (Fig. 1C ), pedicel 1.0-1.5 mm. Flowers 5-merous; sepals and petals only slightly differentiated, persistent in fruit (Fig. 1C ). Calyx tube broadly obconical, ca. 0.5 × 1 mm, lobes narrowly triangular, 1.0-1.2 × 0.5-0.6 mm, basally overlapping corolla lobes, margins minutely denticulate, apex acuminate and often distally reflexed. Corolla lobes broadly triangular, 1.0-1.2 × 0.5-0.7 mm, margins minutely denticulate, apices broadly acute. Stamens 5, at the edge of the floral disc and alternating with corolla lobes. (Only one male plant of Perrottetia taronensis has been seen. It has two remnant undeveloped flower buds with all other flowers already fallen. In Perrottetia the filaments elongate after the male flowers open, so the filament characters in the observed unopened flower buds of P. taronensis are likely not typical of what they would be during anthesis.) Anthers globular, ca. 0.3 × 0.4 mm. Ovary superior, turbinate, ca. 1.2 × 1.0 mm. Fruit a berry, young fruit green but starting to turn red by July and turning purple and becoming fleshy when mature by August, ca. 5 mm in diam. when mature, usually 4-seeded although occasionally with only 2 or 3 seeds developing, apex emarginate; style ca. 0.2 mm, often deciduous, apically 2-parted. Seeds brown, 1.0-1.5 mm in diam., surface with numerous shallow vertical rugose ridges when dry.

Etymology.

The specific epithet " Perrottetia taronensis " refers to the Taron River valley in Myanmar. In China this river is named the Dulong Jiang (Dulong River) (Fig. 4 ). The Taron River flows into the N’Mai Hka ( N’Mai River) which joins the Mali Hka (Mali River) forming one of the main northern tributaries of the Ayeyarwady River (Irrawaddy River).

Habitat and distribution.

The seven collections of Perrottetia taronensis that have so far been made occur in the Ayeyarwady River drainage in both Yunnan Province, China and Kachin State, Myanmar at an elevation range of 1350-1970 m (Fig. 4 ). In China P. taronensis occurs on slopes in subtropical broadleaved evergreen forests, in disturbed secondary forests of Alnus nepalensis D. Don (an early successional tree species of secondary forests in this region), and among shrubs near river banks. In Myanmar, the habitat of the single collection of a male plant is classified within the Kachin Hills subtropical rainforest ecosystem, a closed-canopy humid lower montane forest type occurring between 700-1500 m ( Armstrong et al. 2020; Murray et al. 2020). The six collections in China are from the valley of the Dulong Jiang which drains into the Taron River/ N’Mai Hka in Myanmar, an upper tributary of the Ayeyarwady River. In Myanmar, the single collection is from the Babulongtan mountain range, in the drainage of the Nam Tisang/Mali Hka, which is in the adjacent river system to the west of the N’Mai Hka.

Proposed IUCN Conservation Status.

The proposed Conservation Status of Perrottetia taronensis is Endangered (EN), B1ab(i,ii,iii,v)+2ab(I,ii,iii,v), according to the IUCN Standards and Petitions Committee (2019). This status is based on the criteria of EOO 802.498 km2 and AOO 319.308 km2 calculated by using GEOCAT ( Bachman et al. 2011) and due to the occurrence in a small area, a decline in the quality of its habitat, and the low number of mature individuals observed.

Paratype specimens of Perrottetia taronensis examined.

China. Yunnan Province: Gongshan Xian 贡山县, Dulongjiang Xiang 独龙江乡, Bapo Cun 巴坡村, in the vicinity of Bapo, on the E side of the Dulong Jiang, 1350 m, 27.74°N, 98.35°E (estimated coordinates), 19 November 1990, Dulong Jiang Investigation Team 独龙江考察队 579 (CAS, KUN); Bapo Cun, W side of Gaoligong Shan, W of Gongshan, on the trail from Qiqi 其期 to Bapo in the Dulong Jiang valley, 1900 m, 27.7290°N, 98.3670°E, 17 July 2000, Li Heng 李恒 12931 with Bruce Bartholomew, Philip Thomas, Peter Fritsch, Dao Zhiling 刀志灵, Wang Zhong-lang 王仲朗 & Li Rong 李嵘 (CAS, E, MO); Bapo Cun, W side of the Gaoligong Shan, along Gamalai He (Gamalai River) 嘎莫赖河 and Dulong Valley on the trail from Xishaofang 西哨房 to Bapo, 1350 m, 27.7592°N, 98.3377°E, 18 July 2002, Li Heng 李恒 15072 with Li Rong 李嵘 & Dao Zhiling 刀志灵 (CAS, KUN); Kongdang Cun 孔当村, W side of Gaoligong Shan, along Dulongjiang Valley on the trail from Bapo to Dizhengdang 迪政当, 1550 m, 27.8773°N, 98.3355°E, 21 Jul 2002, Li Heng 李恒 15156 with Li Rong 李嵘 & Dao Zhiling 刀志灵 (CAS, KUN); Xianjiudang Cun 献九当村, W side of Gaoligong Shan along Dulong Jiang Valley on the trail from Kongdang to Dizhengdang, 1560 m, 27.9061°N, 98.3363°E, 23 July 2002, Li Heng 李恒 15230 with Li Rong 李嵘 & Dao Zhiling 刀志灵 (CAS, KUN). Myanmar. Kachin State, Putao District, Naungmung Township, buffer zone of Hkakaborazi National Park, along trail between Maza and Namti, 1763 m, 27.4650°N, 97.6967°E, 18 June 2017, Kate Armstrong 2983 with Thet Yu Nwe, Moe Myint Thu, San Naing Dee, Zaw Naing Tun, Hla Naing Htay & Pa Rang Gang Ken Sar (CAS, E, NY, RAF).

Figures

Figure 1. Perrottetia taronensis A habit, branch with fruit B dactylose leaf bud with young leaves and stipules C fruit with style, mature berry, persistent sepals and petals, and stipe. Illustrated by Alan Chou.

Figure 2. Leaves of Perrottetia taronensis showing also the old male inflorescences, from which all the flowers have dropped A abaxial surface B adaxial surface. Photos in the field of Armstrong et al. 2983.

Figure 3. Young leaves of Perrottetia taronensis showing the distinctive dactylose shape and reddish brown indumentum and also an old male inflorescence, from which all the flowers have dropped. Photo in the field of Armstrong et al. 2983.

Figure 4. Distribution showing the known locations of Perrottetia taronensis in China and Myanmar. The map uses Shuttle Radar Topography Mission (SRTM) 90 m raster elevation data from Jarvis A, Reuter HI, Nelson E, and Guevara E, 2008, Hole-filled seamless SRTM data V 4, International Centre for Tropical Agriculture (CIAT) available from https: // srtm. csi, cgiar. org (Reuter et al. 2007). The elevation intervals for the region shown in this map have been set to 0 - 999 m, 1000 - 1999 m, 2000 - 2999 m, 3000 - 3999 m, and 4000 m and above. All seven collections are from within the 1000 - 1999 elevation interval shown on the map. Within China to the east and separated by the Gaoligong Shan range is the Nu Jiang (Salween River) and farther still to the east is the Lancang Jiang (Mekong River).