Chloroplast analysis supports monophyly of Iris series Tenuifoliae and identifies three new species

A taxonomic and phylogenetic study found strong support for Iris series Tenuifoliae as a monophyletic group within the Xiphion Clade. The researchers combined complete chloroplast genome data with comparative morphology to examine the series’ delimitation, relationships with other Iris groups, internal lineages, structural variation and geographic distribution. The phylogeny included 70 chloroplast genomes from 63 Iris taxa, including 21 genomes newly sequenced for the study.

Two Moraea species were used as outgroups. All 21 newly assembled chloroplast genomes had the typical quadripartite structure, comprising large and small single-copy regions and two inverted repeats. They ranged from 150,596 to 157,200 base pairs, and each contained 113 genes: 79 protein-coding genes, 30 tRNA genes and four rRNA genes.

Gene order was otherwise highly conserved across the sampled members of the series. Comparative analysis identified an approximately 17,000-base-pair inversion in the small single-copy region of seven samples: Iris ventricosa, I. bungei, I. cathayensis, two I. kobayashii samples and two unidentified specimens. The rearrangement reversed eight genes: rps15, ndhH, ndhA, ndhI, ndhG, ndhE, psaC and ndhD.

It was identified as a distinctive structural feature of the series’ second major clade and as evidence for that clade’s monophyly independent of sequence data. The study distinguished four configurations at the inverted-repeat and single-copy boundaries, based on the positions of rps19 and ycf1. Most samples shared the fourth configuration.

I. liupanshanensis and I. qinghainica showed boundary contraction, while I. anguifuga showed expansion that placed ycf1 wholly within the inverted repeat. The series was recovered as sister to the clade containing I. ser. Foetidissimae and I. ser.

Spuriae, while the three newly described species and two unidentified taxa were incorporated into the strongly supported series. Three new species were formally described: Iris liupanshanensis, I. helanshanensis and I. coeruleoviridis. I. liupanshanensis has unusually broad leaves, 10–12 mm wide, and an above-ground flowering stem.

I. helanshanensis differs from I. farreri in its shorter bracts, lack of an elongated ovary neck and beakless fruit. I. coeruleoviridis resembles I. anguifuga but has broader leaves and smaller flowers, measuring 6–6.5 cm in diameter rather than about 10 cm. All three new species were documented in China.

I. liupanshanensis occurs in montane grasslands of the Liupan Mountains, while I. helanshanensis is recorded from the Helan and Luo Mountains. I. coeruleoviridis is known only from the Caolianling area of the western Qinling Mountains. Preliminary conservation assessments placed I. liupanshanensis and I. coeruleoviridis in the Data Deficient category.

I. helanshanensis was assessed as Vulnerable based on an estimated population of fewer than 1,000 mature individuals, an occupied area of less than 20 km² and a limited number of locations. The authors noted potential habitat degradation and fragmentation associated with tourism development, while stating that systematic surveys are needed to verify the assessment. The analysis had several limitations.

No I. songarica sample was available, leaving its phylogenetic position unresolved. Detailed morphological data were also unavailable for the two unidentified taxa, so their status as independent species could not be established. The known range of I. coeruleoviridis remains limited, and some records used to assess distribution were sparse.

Subject of Research: Phylogeny, chloroplast-genome structure and taxonomy of Iris series Tenuifoliae

Article Title: Phylogeny and taxonomy of Iris ( Iridaceae ) series Tenuifoliae : Discovery of a clade with chloroplast genome inversion and description of three new species

Article References: Zhang, Z., Li, H., Zhang, G., & Zuo, T. (2026). Phylogeny and taxonomy of Iris (Iridaceae) series Tenuifoliae: Discovery of a clade with chloroplast genome inversion and description of three new species. PhytoKeys, 275, 299-320. https://doi.org/10.3897/phytokeys.275.184036

Image Credits: AI Generated

DOI: 10.3897/phytokeys.275.184036

Keywords: Iris, Tenuifoliae, phylogenetics, chloroplast genomes, plant taxonomy, species description, genome inversion, Iridaceae, conservation status, Phylogeny, taxonomy, series