Christisonia hekouensis Gui L.Zhang, J.D.Ya & W.B.Yu, 2024

Ya, Ji-Dong, Zhang, Gui-Liang, Tan, Yun-Hong, Zhang, Gui-Sheng, Zhang, Kun, Ping, Shan-Hu, Wang, Dong, Zhang, Wei, Cai, Jie, Randle, Christopher P. & Yu, Wen-Bin, 2024, Two New Species of Christisonia (Orobanchaceae) from Southeastern Yunnan, China, Systematic Botany (Basel, Switzerland) 49 (1), pp. 68-76 : 75

Christisonia hekouensis Gui L.Zhang, J.D.Ya & W.B.Yu , sp. nov. (河口假野菰) TYPE: CHINA. Yunnan Province, Hekou County, Yaoshan, 606 m, under the bamboo forests, 30 July 2017, J.-D. Ya & G.-L. Zhang 17CS16588 (Holotype: KUN! Isotype: KUN!).

Diagnosis — Christisonia hekouensis is similar to C. kwangtungensis in its rose-red corolla, and corolla shape and structure, but can be distinguished from the latter by having persistent (vs. caducous) scalelike leaves, calyx and corolla puberulent externally (vs. glabrous), corolla lobes margin serrulate (vs. entire), style pink and glabrous or sparsely capitate-glandular pubescent above (vs. white and pilose above), with less than 2 mm separating stamens from the style (vs. more than 2 mm).

Root parasitic herb. Stem fleshy, 3.0– 9.5 cm long, ca. 6.0 mm in diam. Leaves scalelike, ovate-triangular, ca. 5.0 mm long, persistent. Inflorescence racemose; bracts toward the base, short and broad, irregular in outline, covering over the base of calyx, outer surface scaberulous, margin ciliate; bracteoles lanceolate, ca. 1.5 3 0.6 cm, glabrous, apex acute; pedicels very short up to 1.6 cm. Calyx red, tubular-campanulate, 1.5–3.0 cm long, puberulent outside, apex 2-(3-)lobed, lobes unequal and dentate, often degraded. Corolla bilabiate, 3.0– 5.5 cm long, red to dark red, mid-lobe with a conspicuous yellow stripe extending to the middle of corolla tube; puberulent outside and inside, clustered hairs in the throat; tube slightly incurved, inflated at the throat, corolla lobes imbricate, margin serrulate; upper lip slightly cucullate, 1.0– 1.5 cm long, 2.0– 2.5 mm broad, 2-lobed; lower lip 1.0– 1.5 cm long, 2.5–3.0 cm broad, 3-lobed, lobes erect spreading, reniform, apex obtuse. Stamens 4, didynamous; filaments 2.5–5.2 cm long, glabrous, ribbon-like, adnate except their distal ends above the middle of the corolla; anthers two-celled, fertile cells ca. 3.5 mm long, sterile cells reduced into a spur and mucronate, ca. 9.0 mm. Style 2.6–5.3 cm long, slightly longer than stamens, incurved, glabrous or sparsely capitate-glandular pubescent above; stigma peltate, 6.0–7.0 mm in diam, white, sometimes purple at the margin, densely pilose. Capsules ovate, ca. 1.8 3 1.5 cm, glabrous, enclosed by persistent calyx, styles persistent when ripe. Figures 1 , 3 .

Phenology —It was observed in flowering from June to July, fruiting from July to August.

Distribution and Habitat —At present, Christisonia hekouensis is currently only known from two populations in Hekou County, Southeast Yunnan, China ( Fig. 5 ). The populations consists of ca. 1000 individuals under the bamboo forests at an elevation of 600 m, which are parasitic on the roots of Indosasa sinica Chu & Chao ( Poaceae ).

Etymology —The new species is named after its type locality, Hekou County, Yunnan, China.

Preliminary Conservation Status —We evaluated the conservation status of Christisonia hekouensis according to the IUCN Red List categories and criteria ( IUCN 2023). This new species is only known from the type locality and adjacent areas. To date, our field surveys identified only two small populations with around 1,000 individuals. We suppose that more populations should be available in Southeast Yunnan and extending to North Vietnam, and population size is not clear, therefore the preliminary conservation status of these species is considered to be Data Deficient (DD).

Additional Specimen Examined (Paratype) — China. — YUNNAN PROVINCE: Hekou County, Yaoshan Town, ca. 600 m, under the bamboo forests, 26 June 2019, C. Liu et al.19CS17998 (KUN).

Figures

FIG. 1. Christisonia hekouensis Gui L. Zhang, J. D. Ya & W. B.Yu sp. nov. A. Habitat. B, C. Flowering plant. D. Flower (lateral view). E, F. Flower (front view). G. Flower (rip cutting). H. Four heteromorphic anthers and stigma (front view). I. Four heteromorphic anthers and stigma (lateral view). J. Anthers and stigma. K, L. Fruit. M. Roots. Photographed by J.-D. Ya and G.-L. Zhang. (All scales indicate 1 cm).

FIG. 3. A–H. Christisonia hekouensis. A. Flowering plant. B. Flower (rip cutting). C. Ovary and stigma. D. Long stamens and anthers. E. Short stamens and anthers. F. Fruit. G. Stigma. H. Flower (lateral view). I–O. Christisonia dentosa. I. Flowering plant. J. Flower (rip cutting). K. Ovary and stigma. L. Long stamens and anthers. M. Short stamens and anthers. N. Stigma. O. Fruit. Drawn by Rong-Mei Zhang.

FIG. 5. Distribution map of the Chinese Christisonia species. Occurrence points were from the Chinese Virtual Herbarium (2023), the Plant Photo Bank of China (2023), the Plants of Taiwan (2023), and other resources (Chen et al. 2017; Xie et al. 2017).