Zhangjiajie bittercress (Cardamine zhangjiajieensis) growing in wet places and only found in Zhangjiajie Nature Reserve

NEWS - Zhangjiajie bittercress (Cardamine zhangjiajieensis Q.R.Liu & J.L.Li, sp. nov.) is only found in Zhangjiajie Nature Reserve, Hunan Province, China, growing in wet places on riverbanks, forests and roadsides. The terminal leaves are stem-shaped, mostly round or oblong, with wavy sinus margins and narrow winged seed tips.

Cardamine L. (Brassicaceae) is a cosmopolitan genus with more than 280 species, most of which are distributed in temperate regions. Since 2001, new species and distribution records in China have been published continuously and so far 61 species have been reported in China, of which 31 are endemic.

Field survey was conducted in Hunan, Sichuan, Jilin, Hebei, Yunnan from 2021 to 2023. During the examination of specimens of the genus Cardamine, researchers selected one specimen identified as Cardamine macrocephala Z. M. Tan & S. C. Zhou (1996) collected from Zhangjiajie Nature Reserve.

This name has been recorded as a synonym of C. circaeoides Hook.f. & Thomson. The morphological characters of the specimen are significantly inconsistent with C. circaeoides. This study conducted field investigation, morphological analysis, systematic and proposed C. zhangjiajieensis as a new species to science.

C. zhangjiajieensis is a perennial herb, 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 pair 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. 2n ≈ 6x.

The new species differs from C. scutata 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), vegetatively propagated by adventitious buds in fruit stage.

The new species is similar to C. circaeoides, but is distinguished by 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).

Based on chloroplast genome data, C. parviflora, C. scutata, C. zhangjiajieensis and C. amariformis form a subclade with C. parviflora at the base of the clade, which supports previous research. C. scutata (2n = 4x = 32) may be involved in the speciation of C. zhangjiajieensis (2n ≈ 6x) as a hybrid parent according to ploidy level.

Another important character of C. zhangjiajieensis is vegetative reproduction by adventitious buds at the fruit stage which is also found in C. hupingshanensis, but C. zhangjiajieensis differs in that it is 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).

C. hupingshanensis has 2n = 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 2n = 3x.

Original research

Li J-L, Zhang C, He Y, Liu Q-R (2024). Cardamine zhangjiajieensis, a new species of Brassicaceae in China. PhytoKeys 248: 293-304, DOI:10.3897/phytokeys.248.119678

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