Christisonia dentosa J.D.Ya, Gui L.Zhang & 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 dentosa J.D.Ya, Gui L.Zhang & W.B.Yu , sp. nov. (齿 冠 假 野 菰) TYPE: CHINA. Yunnan Province: Wenshan Prefecture, Malipo County, 1100 m, under the forest on limestone, 13 Aug 2019, J.-D. Ya & Wei Zhang 19CS18585 (Holotype: KUN! Isotype: KUN!).

Diagnosis — Christisonia dentosa is similar to C. hekouensis in floral morphology, but can be distinguished by its dentate corolla lobe margins (vs. serrulate), internally capitate-glandular pubescent corolla tubes (vs. puberulent), style distinctly capitate-glandular pubescent above (vs. glabrous or sparsely capitate-glandular pubescent), and anthers up to 10 mm below the stigma (vs. less 2 mm).

Root parasitic herb. Stem fleshy, 2.0–4.0 cm long, ca. 4.0 mm in diam. Leaves scalelike, ovate-triangular, ca. 2.0 mm long, persistent. Inflorescence racemose; bracts toward the base, short and broad, irregular in outline, covering over the base of calyx, outer surface scaberulous, sparsely puberulent; pedicels very short, ca. 0.2 cm. Calyx red, tubular-campanulate, 2.0–3.0 cm long, sparsely puberulent outside, apex 2-lobed; lobes lanceolate, unequal, apex acuminate. Corolla bilabiate, 4.5–6.5 cm long, red, with a conspicuous yellow stripe extending from inside the lowest lobe to the middle of corolla tube; puberulent outside, capitate-glandular pubescent inside, clustered hairs in the throat; tube inflated at the throat, corolla lobes imbricate, margin dentate; upper lip slightly cucullate, 1.0– 1.5 cm long, 1.8–2.3 mm broad, 2-lobed; lower lip 1.0– 1.5 cm long, 3.0– 3.8 cm broad, 3-lobed, lobes erect, spreading, reniform. Stamens 4, didynamous; filaments 3.0–5.0 m 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. 3.0 mm. Style 4.0–6.0 cm long, distinctly longer than stamens, upper capitate-glandular pubescent; stigma peltate, ca. 9.0 mm in diam, white, purple at the margin, densely pilose. Capsules ovate, ca. 2.0 3 1.4 cm, glabrous, enclosed by persistent calyx, styles persistent when ripe. Figures 2 , 3 .

Phenology —It was observed in flowering in August.

Distribution and Habitat —At present, C. dentosa is currently known only from the type locality in Malipo County, Southeast Yunnan, China ( Fig. 5 ). The population consists of ca. 300 individuals under the bamboo forests in limestone mountains at an elevation of 1100 m. These are parasitic on the roots of Melocalamus arrectus Yi ( Poaceae ).

Etymology —The specific epithet refers to the dentate corolla lobes of this new species.

Preliminary Conservation Status —We evaluated the conservation status of Christisonia dentosa according to the IUCN Red List categories and criteria ( IUCN 2023). To date, this new species is only known from the type locality with around 300 individuals. We suppose that more populations may exist and population size is not clear, therefore the preliminary conservation status of these species is considered to be Data Deficient (DD).

Figures

FIG. 2. Christisonia dentosa J. D. Ya, Gui L. Zhang & W. B.Yu sp. nov. A. Habitat. B, C. Flowering plant. D. Flower (lateral view). E. Flower (front view). F. Flower (rip cutting). G. Four heteromorphic anthers and stigma (front view). H. Four heteromorphic anthers and stigma (dorsal view). I. Fruit. Photographed by J.-D. Ya. (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).