Lilium saccatum

Lilium saccatum
S. Y. Liang (1987)

(Xizang Lily / Sack-based Lily — “袋状百合”)

Overview

Section: Sinomartagon
Origin: Southeastern Xizang (Tibet Autonomous Region, China) — Milin and Bomi Counties, eastern Himalaya
Habitat: Mountain slopes, mixed subalpine grass–shrub communities (ca. 2,800–3,200 m)
Type: Herbaceous, nodding bell-flowered lily
Status: Rare; narrowly distributed in eastern Tibet

Description

Originally described by S. Y. Liang (1987), Lilium saccatum is a small to medium-sized perennial lily (ca. 40–60 cm) characterized by nodding, campanulate, purple-red flowers with dark adaxial spotting. Tepals are recurved at the tips, each showing a shallow basal sac (saccate structure)—the feature from which the epithet saccatum (“pouched”) derives. O(n short, it looks like an old tea bag hanging from a short stalk.

Leaves are ovate to elliptic-lanceolate, alternately arranged or forming loose subwhorls, 6–10 cm × 0.5–1.5 cm, occasionally densely clustered near the stem apex. Bulbs are small and white with overlapping scales.

Flowering typically occurs July–August. Anthers are bright yellow, and the nectary furrows are glabrous to slightly papillose.
Habitat and Ecology

Field observations and herbarium records locate this species on humid mountain slopes in Milin County, southeastern Xizang, within the eastern Himalayan corridor.

The native environment experiences cool, wet summers and cold, dry winters, with frequent mist and high UV exposure typical of subalpine valleys.

Its solitary nodding flowers and dark-spotted tepals suggest adaptation to moth or bee pollination, similar to L. souliei and L. lophophorum, with which it co-occurs.

Genome and Phylogeny

A complete chloroplast genome of Lilium saccatum was published in 2024 (Xu et al., Mitochondrial DNA Part B).

  • Genome size: 151,839 bp

  • Structure: Typical quadripartite cpDNA

  • LSC = 81,469 bp

  • SSC = 17,528 bp

  • IR = 26,421 bp × 2

  • Gene content: 113 unique genes (79 PCGs, 30 tRNAs, 4 rRNAs)

  • GC content: 37.0 %

  • Introns: 20 genes with introns; rps12 exhibits three exons (trans-spliced).

  • GenBank accession: OR353687

Phylogenetic results (24 species, ML tree):
L. saccatum forms a tight clade with L. souliei, confirming previous suspicions that it represents either a geographically restricted variant or an incipient segregate lineage within the souliei complex.

Simplified cp-based topology
┌── L. souliei
┌───────────┤
│ └── L. saccatum
Section
Sinomartagon ────┤
│
├── L. henricii
├── L. bakerianum
├── L. amoenum
└── L. nepalense

Taxonomic Remarks

Earlier distinctions based on tepal shape and basal sacs have proven insufficiently diagnostic.

Yang & Zhuang (2015) formally proposed synonymizing L. saccatum with L. souliei after comparative morphological study.

However, genomic evidence (Xu et al., 2024) shows minor but consistent cpDNA divergence (565 singleton variable sites in a 153 kb alignment), implying that L. saccatum may represent a recently isolated or micro-evolved population rather than a pure synonym.

For now, it is reasonable to regard L. saccatum as a closely allied subspecies-level taxon within the L. souliei complex pending nuclear genome comparison.

Conservation and Cultivation

Native stands are scarce and threatened by road expansion and grazing in Milin and Bomi.

The species has high ornamental value for its compact size and richly colored flowers.

Cultivation trials remain limited, but specimens used for cpDNA sequencing were grown successfully from field collections under controlled conditions at the Chengdu Institute of Biology (CDBI).

Evolutionary Context

Lilium saccatum belongs to the Himalayan–Southeastern Plateau lineage of Sinomartagon, bridging western (nepalense–henricii) and eastern (souliei–amoenum) groups.

This region, marked by orogenic uplift and monsoon variability, has fostered strong micro-endemism, and L. saccatum may represent an ecological derivative of L. souliei specialized for cooler, higher-elevation habitats in southeastern Tibet.

References

Xu, Bo, et al. “Complete chloroplast genome of Lilium saccatum (Liliaceae) from southeastern Xizang, China.” Mitochondrial DNA Part B: Resources 9, no. 8 (2024): 1624–1630. https://doi.org/10.1080/23802359.2024.2403410.

Liang, S. Y. “New species of Lilium from Xizang.” Acta Botanica Yunnanica 9 (1987): 73–76.

Yang, X. & Zhuang, X. “Lilium saccatum: A new synonym of L. souliei (Liliaceae) for the Flora of China.” Phytotaxa 212 (2015): 87–92.

Duan, Y. et al. “Molecular phylogeny and biogeography of Lilium.” Botanical Journal of the Linnean Society 199 (2022): 323–341.

Gao, Y. et al. “Phylogenetic relationships of Lilium based on cpDNA genes.” Plant Systematics and Evolution 301 (2015): 1139–1152.