Cardamine zhangjiajieensis Q. R. Liu & J. L. Li 2024, sp. nov.

Cardamine zhangjiajieensis Q. R. Liu & J. L. Li sp. nov. Figs 4, 5 Type. China • Hunan: Zhangjiajie Nature Reserve, Wulingyuan, 29.340766°N, 110.45326°E, 880 m, May 21, 2022, Li JL, Zhang C, BNU 2022 ZJJ 02 (holotype: BNU 0057018, isotype: BNU 0057017, BNU 0057016). Diagnosis. Cardamine zhangjiajieensis is similar to C. circaeoides. From the latter, C. zhangjiajieensis is readily distinguished by the terminal leaflet of the cauline leaf 4.5–7 cm (vs. 2.5–4.5 cm), lateral leaflets 0–2 pairs (vs. 0–1 pairs), without auriculate petioles (vs. auriculate petioles), mostly round or oblong (vs. oblong-oval to triangular-oval), margin undulating sinuses (vs. crenate or subentire), seed apically narrow wing (vs. wingless). Description. Herbs perennial, 15–40 cm tall, glabrous. Rhizomes short, sometimes with a few stolons. Stems erect, simple or branched above middle. Basal leaves not rosette, simple or 2–4 foliolate; petiole 3–6 cm, glabrous; leaf blade or terminal leaflets cordate or ovate, 3–5 cm × 3–5 cm, glabrous, base cordate, sometimes subtruncate, or subcuneate, margin often sinuous, apex obtuse; lateral leaflets (when present) petiolulate or sessile, much smaller than terminal one. Cauline leaves simple or 1 of which 2 – or 3 – foliolate, petiolate or rarely uppermost subsessile; petiole (0.4 –) 1–5 (– 6) cm; leaf blade similar to that of basal leaves, cordate, sometimes ovate to ovate-lanceolate, 4.5 (– 6) × 3 (– 4) cm. Fruiting pedicels 3–12 (– 15) mm, ascending, base sometimes rooting, emitting new plants. Sepals ovate or oblong, 2.8–3.2 mm × 1.4–1.9 mm, glabrous, margin often membranous. Petals white, spatulate, 4.5–6.5 mm × 2.5–3 mm, apex notch. Median filament pairs 3.5–4.5 mm, lateral pair 1.5–2.5 mm; anthers oblong. Siliques linear, 2.5–4 cm; valves torulose, glabrous; style (0.5 –) 1–2 mm. Seeds brown, ovate or broadly oblong, 1.4–1.6 × 0.9–1.1 mm, with a narrow wing. Fl. and fr. April – Jul. 2 n ≈ 6 x. Distribution. Only found in Zhangjiajie Nature Reserve, Hunan Province, grows in wet places of roadside, forest, river sides. Specimens examined. China • Hunan: Zhangjiajie Nature Reserve, Wulingyuan, 29.324980°N, 110.433310°E, 600 m, May 21, 2022, Li JL, Zhang C, BNU 2022 ZJJ 06 (BNU, 4 duplicates) • Zhangjiajie Nature Reserve, Wulingyuan, 29.341153°N, 110.457903°E, 820 m, May 21, 2022, Li JL, Zhang C, BNU 2022 ZJJ 04, (BNU, 7 duplicates); April 25, 2023, Li JL, Song QR, BNU 2023 ZJJ 01, (BNU, 2 duplicates); Jinbianxi, 2021, Zhang C zhang 670, (BNU, 7 duplicates) • Tianmenshan, May 2, 2013, Zhang DG 130502028 (JIU 33520) • Hunan, Exact location unknown, March 18, 1955, Xia JL 20, (PE 01995438). Discussion. Major centers of Cardamine diversity estimated by the number of taxa appear to be in the European Mediterranean and the Caucasus; Eastern Asia and the Himalayas; and North and Central America (Marhold et al. 2018). Utilizing data from this study, we selected common Cardamine in Hunan and Central China, such as Cardamine lyrata, Cardamine anhuiensis, Cardamine engleriana, Cardamine fragariifolia, Cardamine circaeoides, Cardamine scutata, Cardamine fallax, Cardamine occulta and determined the phylogenetic position of C. zhangjiajieensis within the genus. Phylogenetic analysis shows that C. zhangjiajieensis falls in a clade sister to C. scutata. From the latter, C. zhangjiajieensis is readily distinguished by lateral leaflets 0–2 pairs (vs. 1–4), the terminal leaflet of the cauline leaf 4–7 cm × 3.5–6.5 cm (vs. 2–5 × 1.5–4 cm), petals 4.5–6.5 mm × 2.5–3 mm (vs. 2.5–4.5 × 1.5–2.5 mm), sepals 2.8–3.2 mm × 1.4–1.9 mm (vs. 1.5–2.5 × 0.9–1.4 mm), vegetative propagated by adventitious buds in fruit stage. As a widespread species in East Asia, the speciation of C. scutata has been elucidated. Allotetraploid C. scutata originated by hybridization between two diploid species, C. parviflora and C. amara (Mandáková et al. 2019). Based on chloroplast genome data, our study showed that C. parviflora, C. scutata, C. zhangjiajieensis, C. amariformis formed a highly supported subclade, C. parviflora located at the base of clade, which supported the results of previous studies. Our analysis also suggested that C. scutata (2 n = 4 x = 32) may be involved in the speciation of C. zhangjiajieensis (2 n ≈ 6 x) as hybrid parent according to the ploidy level. Another notable character of C. zhangjiajieensis is vegetative reproduction by adventitious buds in fruit stage, which is also found in C. hupingshanensis, an endemic species to Hupingshan Mountains (Long 2004). From the latter, C. zhangjiajieensis is readily distinguished by glabrous (vs. hirsute), terminal leaflet of the cauline leaf oblong, not petiole auriculate-amplexicaul at base (vs. reniform or orbicular, petiole auriculate-amplexicaul at base), seed apically narrow wing (vs. wingless), as shown in Table 4. C. hupingshanensis has 2 n = 24. In natural conditions, the reproduction of C. hupingshanensis relies on adventitious roots growing on each stem node after lodging, indicating that the ploidy level of C. hupingshanensis is 2 n = 3 x. To further clarify speciation and evolution of karyotype within Cardamine, studies with comprehensive sampling and seeds germination of C. zhangjiajieensis are needed.