New Pink-Flowered Plant Species Discovered in Guangxi’s Karst Valleys

Deep in a dark, moist valley within Qichong National Nature Reserve in China's Guangxi Zhuang Autonomous Region, botanists have identified a striking new species of flowering plant that has now been formally described as Hemiboea siccinvolucris, a member of the African violet family Gesneriaceae. The story began in October 2014, when a field survey in the reserve near Hezhou City turned up a population of Hemiboea that did not match any known species. Growing on limestone hillsides at an elevation of roughly 171 meters, the plants stood out immediately.

Unlike their smooth-stemmed relatives, they bore pubescent, or hairy, leaves and stems. Their involucres, the spherical protective bracts that enclose the flower clusters, dried out early, before the flowers even opened, an unusual trait in this genus. The corollas were pale pink rather than the white, pale yellow, or pink shades typical of many congeners, and the plants flowered late in the year, from November to December.

To confirm that this population truly represented a species of its own, the research team, led by B. Pan and Y. B. Lu, combined careful morphological study with molecular phylogenetic analysis. They documented the morphology and flowering phenology of approximately thirty mature individuals in the wild and ten plants cultivated at the Guangxi Institute of Botany. Herbarium specimens and digitized type specimens from collections including K, E, P, MPU, and UC, along with digital material from several Chinese herbaria, were examined in detail, with particular attention paid to the closely related species H. subcapitata, H. cavaleriei, and H. liana.

The morphological case for a new species rests on a consistent suite of differences. H. siccinvolucris plants are 30 to 55 centimeters tall with pubescent stems, whereas H. cavaleriei ranges from 20 to 150 centimeters and is glabrous, H. subcapitata spans 10 to 40 centimeters and is glabrous to pubescent, and H. liana reaches 10 to 46 centimeters with glabrous stems. The leaves of the new species are densely hairy on their upper surfaces and sparsely hairy below, a pattern not seen in the comparison species.

Its flowering stems bear terminal cymes of one to three flowers, while its relatives produce pseudoterminal clusters of three to twelve flowers, or in H. liana's case usually a single terminal flower. None of the three comparison species is recorded with early desiccation of the involucre. Floral anatomy adds further distinguishing detail.

The anthers of H. siccinvolucris are elliptical and only 1.5 to 1.7 millimeters long, markedly smaller than those of H. cavaleriei at 3 to 3.2 millimeters or H. subcapitata at 3.5 to 4.5 millimeters. The stigma is reniform, or kidney-shaped, rather than obtuse or shallowly bilobed as in its relatives. The corolla itself is pale pink outside with scattered pink spots, densely glandular-puberulent, and marked inside with prominent purple striations and maculations, with a ring of hairs positioned 4.5 to 6.0 millimeters above the corolla base.

Flowering timing also separates the species: H. cavaleriei and H. subcapitata bloom from August to October, while H. liana flowers from November into January, overlapping but not identical to the new species' November to December window. For the molecular work, the team collected leaf samples from three individuals of the putative new species and one individual each of five known species: H. liana, H. lutea, H. roseoalba, H. shimentaiensis, and H. subcapitata. Genomic DNA was extracted using a modified CTAB technique, and sequencing libraries with insert sizes of approximately 350 base pairs were run on an Illumina NovaSeq 6000 platform in paired-end 150 mode, with each sample yielding more than 3.15 gigabases of raw data.

The researchers then assembled complete ribosomal DNA internal transcribed spacer regions and whole chloroplast genomes de novo using GetOrganelle, annotating the plastid genomes with CPGAVAS2 against a reference genome from H. yongfuensis. All new sequences were deposited in the NCBI database. The phylogenetic analysis drew on 33 published ITS sequences and 13 complete chloroplast genomes of Hemiboea retrieved from NCBI, analyzed alongside the newly generated data, with species of Lysionotus and Petrocosmea serving as outgroups.

The aligned matrices contained 640 characters for ITS and 153,682 for the chloroplast genomes, including 233 and 7,038 variable sites respectively. Notably, an Incongruence Length Difference test with 1,000 permutations revealed significant conflict between the two datasets, with a p-value of 0.001, so the researchers analyzed them separately rather than combining them. Maximum likelihood and Bayesian inference methods produced congruent topologies within each dataset.

Both analyses confirmed that Hemiboea is monophyletic with maximal support, and that all sampled individuals of the new species form a coherent lineage with full support, bootstrap values of 100 percent and posterior probabilities of 1.00. But the two genomes disagree on its closest kin. The chloroplast phylogeny places H. siccinvolucris as sister to H. subacaulis, together forming a strongly supported clade with H. subacaulis var. jiangxiensis.

The nuclear ITS tree instead positions it as sister to a clade containing H. follicularis and H. purpurea, though with only moderate support of 68 percent bootstrap and a posterior probability of 0.69. The chloroplast matrix shows higher consistency and lower homoplasy than the ITS matrix, suggesting a more reliable phylogenetic signal from the plastid data. This kind of nuclear-plastid discordance is well documented in Gesneriaceae.

Previous work in the subtribe Didymocarpinae has attributed topological conflict between nuclear and plastid genomes to ancient hybridization and gene flow, and in the genus Henckelia, cytonuclear discordance has been linked to incomplete lineage sorting and hybridization associated with polyploidization. The authors suggest that the evolutionary history of H. siccinvolucris may similarly involve reticulate processes such as hybridization or introgression, though they also caution that methodological limitations, including limited informative sites and restricted taxon sampling, could contribute to the conflicting placements. Broader sampling and higher-resolution molecular markers will be needed to pin down the species' precise phylogenetic position.

Whatever its exact ancestry, H. siccinvolucris is morphologically distinct from the species its phylogenies flag as relatives. Compared with H. subacaulis, it has much taller stems, 30 to 55 centimeters against 5 to 22.5 centimeters. Compared with H. purpurea and H. follicularis, its calyx is deeply divided to the base into free, long-elliptic or linear-lanceolate lobes rather than fused above the middle, its corolla is pale pink with purple stripes rather than uniformly purple or white, its corolla tube is densely glandular-pubescent externally rather than glabrous, and its leaves are pubescent on both surfaces rather than glabrous.

The species' epithet, siccinvolucris, refers to its signature trait, the involucre that becomes dry and scarious before the flowers open, and its Chinese name is Gan bao ban shuo ju tai. The new species is currently known only from its type locality, the low-altitude, moist gully margins of Qichong Nature Reserve in Zhaoping County, where it grows alongside Illicium simonsii, Impatiens tubulosa, Ophiorrhiza pumila, Elatostema acuminatum, the tree fern Alsophila spinulosa, and Dicranopteris pedata. Fewer than 200 individuals have been recorded, and while undiscovered populations may exist in similar habitats, the species' population size, reproductive capacity, and habitat adaptability have not yet been quantitatively assessed.

Under IUCN Red List criteria, the authors have provisionally classified it as Data Deficient. The discovery underscores how much remains undocumented in China's karst flora, a region where paleoclimatic fluctuations and niche heterogeneity are thought to have driven explosive radiations and exceptional endemism, and where each new species adds a piece to the evolutionary puzzle of one of the world's great biodiversity hotspots.

Subject of Research: Description of a new Gesneriaceae plant species from Guangxi, China, using morphology and molecular phylogenetics

Article Title: Hemiboea siccinvolucris ( Gesneriaceae ), a new species from northeastern Guangxi, China

Article References: Fang, Y., Pan, B., Li, P.-W., Qin, X.-M., Zhang, Q., & Lu, Y.-B. (2026). Hemiboea siccinvolucris (Gesneriaceae), a new species from northeastern Guangxi, China. PhytoKeys, 274, 289-301. https://doi.org/10.3897/phytokeys.274.185059

Image Credits: AI Generated

DOI: 10.3897/phytokeys.274.185059

Keywords: Hemiboea siccinvolucris, Gesneriaceae, new species, Guangxi, karst biodiversity, molecular phylogenetics, chloroplast genome, ITS sequences, taxonomic description, Qichong Nature Reserve, cytonuclear discordance, plant conservation