Morphology and ITS DNA distinguish new Sida species in northern India

A new species of the mallow family has been identified from disturbed roadsides and wasteland in northern India, based on consistent differences in its form, reproductive structures and DNA sequences. The plant, named Sida gathwalarum, was formally distinguished from its closest-looking relative, Sida angustifolia, and from other members of the taxonomically difficult genus Sida. The authors describe it as an erect, highly branched subshrub that can reach 2 metres in height, with small pale-yellow flowers and fruit structures that remain partly enclosed by an enlarged, soft calyx.

The discovery was made during field surveys conducted from 2023 to 2025 in Meerut and Saharanpur districts in Uttar Pradesh and in Roorkee, Haridwar district, Uttarakhand. The researchers encountered five samples in total, growing in open roadside and wasteland habitats. Some populations initially appeared to be unusual variants of Sida angustifolia, but examination of living plants showed that their features were stable and consistently different. Comparisons with historical descriptions, type specimens, regional floras and herbarium material ultimately supported recognition of an undescribed species rather than another form of an existing taxon.

The taxonomic investigation combined observations of fresh and dried specimens with DNA analysis. Living plants supplied all measurements used in the formal comparison, while the authors examined material deposited in the DD and BSD herbaria and high-resolution images from the CAL, BSA, K and P virtual herbaria. Eleven taxa representing nine species, one subspecies and one variety were critically examined against the new plant. A Euromex DZ5040 microscope was used for detailed observation, and images were made with Nikon D5600 and Canon EOS 1300D cameras. Morphological terminology followed Beentje and Simpson. Voucher specimens from the study were deposited in the BSD and DD herbaria.

Sida gathwalarum is an erect, highly branched suffrutex with a green stem that is occasionally bicoloured, one face green and the opposite brownish. Its branches are alternately and spirally arranged, terete and covered with stellate hairs. Leaves vary from narrowly lanceolate to ovate, measuring 5.0–45 millimetres long and 1.0–17 millimetres wide, with acute to acuminate tips and cuneate to rounded bases. Their margins are finely serrate, and the lower surfaces are densely covered with minute stellate hairs. The leaves show prominent pinnate venation, with three to five main nerves arising at the base and four to seven pairs of lateral nerves.

Several features separate the new plant from Sida angustifolia, which it most closely resembles in overall habit. The new species may grow to 2 metres rather than about 1 metre. Its petioles are short, measuring 2.0–5.0 millimetres, and lack the three spiny emergences found at the leaf bases of S. angustifolia. Its stipules are also smaller and narrowly lanceolate to linear-lanceolate, measuring 1.5–3.0 by 0.5–1.0 millimetres, rather than the larger, falcate structures of the comparison species. The new species has cuneate to rounded leaf bases rather than the truncate or cordate bases reported for S. angustifolia. The published identification treatment uses the absence of petiolar spurs, spiral rather than distichous leaves, and dissimilar mericarps to distinguish the new taxon from close members of the Indian flora.

The flowers of Sida gathwalarum are axillary, usually occurring two or more together, pale yellow and bisexual. The peduncle is 1.0–2.0 millimetres long, while the pedicel measures 1.5–2.5 millimetres and is usually articulated below its midpoint. The five-lobed calyx is campanulate, 10-nerved and becomes enlarged around the fruit; its outer surface bears both simple and stellate hairs, while the inner surface is glabrous. Five petals measure 7.0–9.0 by 4.0–4.5 millimetres and have retuse to nearly entire apices rather than the deeply emarginate apices described for S. angustifolia. The stamens number 27–30 and are grouped into five bundles, with a pubescent staminal tube approximately 3.5 millimetres long.

The reproductive structures also include a hairy ovary with five to six carpels, yellow styles divided almost from the base and unequal in length, and yellow capitate stigmas. The description records axile placentation, although the ovules were not all of exactly the same size. Fruit characters provide some of the clearest distinctions from S. angustifolia. The fruit of the new species is described as indehiscent, and its fruiting calyx is soft and compressible rather than firm. The mericarps are heteromorphic, meaning that they differ in form, and number five or occasionally six rather than the five uniform mericarps reported for S. angustifolia.

Mature mericarps of Sida gathwalarum are trigonous to globose, measuring 3.0–3.5 by 1.0–2.0 millimetres, and have coarsely rugose to tuberculate surfaces with irregular lumps and wrinkles. Each bears two apical awns, 1.0–1.5 millimetres long, and a shallow, broad, U-shaped notch. The mericarps do not fill the enlarged calyx equally, and most remain embedded within its cup rather than being shed readily. The seeds are about 2 millimetres long, subtrigonous and slightly asymmetrical, with unequal sides, a rounded rather than sharply pointed dorsal ridge, and a uniformly dull brown to grey-brown colour. In S. angustifolia, the seeds are described as more regularly trigonous, symmetric and variable in colour from brownish to black.

For the molecular analysis, the researchers extracted genomic DNA from fresh plant material, amplified the nuclear ribosomal internal transcribed spacer region and sequenced the products by the Sanger dideoxy chain-termination method. The resulting chromatograms were inspected in FinchTV, with low-quality and ambiguous base calls trimmed, and forward and reverse reads assembled into consensus sequences in DNA Baser. The full dataset contained 18 sequences. Two represented S. gathwalarum and were generated from specimens collected at different locations; sequences for Sida angustifolia and Sida spinosa were also newly generated. Twelve sequences from other Sida species and two outgroup sequences were retrieved from NCBI, while the newly produced sequences were designated for submission to the database following publication.

Multiple sequence alignment was performed with MAFFT, followed by manual inspection and adjustment in MEGA to remove poorly aligned or ambiguous regions and preserve positional homology. A Kimura two-parameter substitution model was selected with jModelTest under the Akaike Information Criterion. Maximum-likelihood analysis in MEGA used 1,000 bootstrap replicates, while Bayesian inference in MrBayes used two independent runs with four Markov chain Monte Carlo chains, each run for 1,000,000 generations and sampled every 100 generations. The first 25% of sampled trees were discarded as burn-in, and the remaining trees were used to produce a majority-rule consensus. Both analytical approaches placed Sida gathwalarum as a distinct, well-resolved lineage within Sida, closely allied to Sida acuta but separated from it by a distinct branch. The relevant clade received 100% posterior probability and 100% bootstrap support. Because the analysis involved the ITS region and a limited set of taxa, the result establishes a distinct placement within the sampled phylogeny rather than reconstructing the evolutionary history of the entire genus. The researchers consequently placed the new species in Sida section Sidae, alongside S. acuta.

The plant is currently known from scattered localities in Meerut and Saharanpur districts of Uttar Pradesh and Roorkee in Haridwar district of Uttarakhand. It occurs in open roadsides and wastelands, sometimes growing together with Sida acuta and Sida rhombifolia subsp. retusa. Other plants recorded at the sites include Achyranthes aspera, Triumfetta rhomboidea, Urena lobata, Setaria verticillata, Cynodon dactylon, Digitaria ciliaris and Oplismenus burmannii. Flowering and fruiting occur through most of the year, with flowers opening around 11 a.m. in summer and after noon in winter. The specific epithet honors the Gathwala, or Gathwal, Khap community to which the discoverers belong. Although its known sites are vulnerable to urban development and other anthropogenic disturbance, the authors consider the species more likely underreported than genuinely rare and recommend that it be assessed as Least Concern under the IUCN Red List.

Subject of Research: Taxonomic identification of Sida gathwalarum, a new mallow species from northern India

Article Title: Sida gathwalarum ( Malvaceae ), a new species from India

Article References: Malik, S., Malik, I., & Malik, V. (2026). Sida gathwalarum (Malvaceae), a new species from India. PhytoKeys, 274, 321-333. https://doi.org/10.3897/phytokeys.274.191644

Image Credits: AI Generated

DOI: 10.3897/phytokeys.274.191644

Keywords: Sida gathwalarum, new plant species, plant taxonomy, Malvaceae, morphological analysis, ITS phylogeny, DNA sequencing, northern India, roadside flora, biodiversity, Sida, gathwalarum