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Article

Clarifying the Taxonomic Relationships of Tulipa iliensis and T. thianschanica Based on Multiple Evidences of Phenotypic, Karyotype, Molecular, and Chloroplast Genomes

by
Huimin Zhang
1,2,
Xiyong Wang
2,3,4,*,
Huawei Liu
2,3,5,
Shiqing Liu
2,6 and
Yan Wei
1,*
1
College of Grassland Science, Xinjiang Agricultural University, Urumqi 830052, China
2
Xinjiang Key Laboratory of Biodiversity Conservation and Application in Arid Lands, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
3
State Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
4
Turpan Eremophytes Botanical Garden, Chinese Academy of Sciences, Turpan 838008, China
5
Xinjiang Key Lab of Conservation and Utilization of Plant Gene Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
6
College of Life Sciences, Shihezi University, Shihezi 832003, China
*
Authors to whom correspondence should be addressed.
Diversity 2025, 17(3), 219; https://doi.org/10.3390/d17030219
Submission received: 1 March 2025 / Revised: 18 March 2025 / Accepted: 18 March 2025 / Published: 20 March 2025
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Versions Notes

Abstract

:
In China, the genus Tulipa L. has been identified as a national second-class protected plant. Due to the complex evolutionary and genetic backgrounds of tulips, the taxonomy of the genus Tulipa and its species remains a matter of dispute. The current study is dedicated to clarifying the taxonomic relationship between two closely related species, T. iliensis and Tulipa thianschanica, by integrating morphological, karyotypic, and molecular evidence—a novel framework for resolving taxonomic ambiguities in closely related species. Morphological analyses showed significant differences in filament shape, pistil length, overall plant height, presence or absence of stem hairs, and perianth length and width, which supports the conclusion that they are distinct species (p < 0.001). Karyotype analysis further verified disparities in their chromosome morphology, and distinct karyotype indices and scatter plot distributions suggest differences between the two species. Molecular phylogenetic analyses using Internal Transcribed Spacer sequences (ITSs) and chloroplast genomes confirmed the genetic differences between T. iliensis and T. thianschanica, and there is evidence indicating the possible occurrence of hybridization events. The research findings demonstrate that T. thianschanica and T. iliensis are independent species, thereby providing valuable insights into the taxonomy of wild tulips and contributing to the conservation of these protected species.

1. Introduction

Tulipa L. is a perennial bulbous herb of the Liliaceae family [1] renowned for its elegant appearance and numerous species and cultivars. Often referred to as the “Queen of Flowers”, tulips are world-famous flowers and the national flower of countries like the Netherlands and Turkey [2]. Tulips are believed to have originated along the Mediterranean coast, in Turkey, and in Central Asia [3], with China and Central Asia, specifically the Tianshan Mountains range and Pamir Plateau, being key centers of origin for the genus Tulipa. About 40% of the world’s tulips resources are found in these regions, which continue to be the primary locations of distribution of wild tulips species. With 14 species, or 83% of all Chinese tulips, Xinjiang possesses the richest tulip germplasm resources in China, mostly in Tianshan, Tacheng, and Altay [4].
Tulipa iliensis Regel is the most widely distributed tulip species, found in deserts of the premontane plains and the steppes of lower mountains at altitudes of 400–1100 m, primarily along the northern slope of the Tianshan Mountains [5]. Tulipa thianschanica Regel has a narrower distribution, occurring in montane grasslands at altitudes of 1000–1800 m, primarily in the western part of the Tianshan Mountains. Research evaluating the ornamental value, utilization potential, and ecological adaptability of tulip varieties has found that T. iliensis and T. thianschanica exhibit superior ornamental characteristics compared to other tulips species [6,7,8]. Both species display excellent ecological adaptability, medicinal properties, and reproductive value. However, the excessive exploitation of wild tulip populations and environmental degradation have slowed natural regeneration, leading to Tulipa species being classified as second-grade protected plants in China [9,10,11].
The phenotypic traits of tulips are primarily represented by flower, bulb, and leaf characteristics. Besides conventional morphological studies, previous research has used micromorphological tools to study tulips [12]. Tan and colleagues systematically investigated the morphological, epidermal, and pollen characteristics of 15 tulips species from China and 3 from Turkey, revealing genus-level relationships but no definitive conclusions regarding interspecies taxonomic relationships [13,14,15]. Li and colleagues further studied the micromorphology of the leaves, pollen, and seed coats of T. iliensis and T. thianschanica, concluding that these species are closely related among the group sect. Leistemones Boiss [16].
DNA barcoding is crucial for species identification, genetic diversity assessments, and population monitoring in the conservation of endangered Tulipa species [17,18]. Tan et al. analyzed 21 tulip species using nrDNA ITSs and cpDNA trnL-F markers, revealing that the phylogenetic positions of T. thianschanica and T. iliensis varied with the selection of outgroups, though their overall relationships remained similar. Previous studies using other molecular markers have also investigated these two tulip species. For instance, in an ISSR-based study of 5 wild tulips from Xinjiang and 19 cultivated tulips, Ju et al. found that T. iliensis exhibited closer genetic affinity to Tulipa altaica than to T. thianschanica among wild tulips. In an RAPD-based study of Xinjiang wild and cultivated tulips, Luan et al. reported a Nei’s genetic distance of 0.07 between T. altaica and T. thianschanica (indicating closest relatedness), while the distance between T. iliensis and T. thianschanica was 0.14. Conversely, Qin et al. analyzed the microsatellite sequence characteristics of the T. iliensis chloroplast genome and constructed phylogenetic trees using 12 cpDNA fragments. These trees showed T. iliensis clustering with T. thianschanica, suggesting closer genetic relationships between them [19,20,21].
Due to their low mutation rates, ease of amplification, and conserved sequences, chloroplast genomes are effective for molecular taxonomy [22,23,24]. Chloroplast whole genomes provide greater accuracy in phylogenetic analysis, making them useful for species with minimal interspecific differences [25]. Studies on the chloroplast genomes of wild tulips, including T. thianschanica, T. iliensis, and others, have contributed valuable insights to phylogenetic studies and species differentiation [26,27].
During fieldwork, we observed that T. thianschanica often coexists within the range of T. iliensis, and both species share morphological similarities, making field identification challenging. Morphological identification, although intuitive, is susceptible to environmental variability. Previous studies have relied on a limited number of gene fragments or a single analytical method, failing to comprehensively consider the complex genetic variation and environmental adaptation processes that species have experienced during their long evolutionary history. This has resulted in persistent uncertainties in reconstructing their precise phylogenetic relationships, further compounded by taxonomic ambiguities. Notably, T. thianschanica is listed as a synonym of T. iliense in the POWO (Plants of the World Online, https://powo.science.kew.org (accessed on 19 February 2025) database, a discrepancy that underscores the urgency of resolving their systematics. To improve plant identification accuracy, we applied a combined approach involving morphological characteristics, karyotype analysis, and molecular markers. This study aims to clarify the taxonomic relationships between T. iliensis and T. thianschanica using three lines of evidence: (1) key morphological characters (filament shape, outer flower width, stylar length, etc.); (2) karyotype analysis, including inter-chromosomal indices; and (3) molecular phylogeny based on nuclear ITS data and chloroplast genome sequences. Together, these findings will elucidate the evolutionary relationship between these two tulip species.

2. Materials and Methods

2.1. Plant Material

A total of 146 samples of T. iliensis and T. thianschanica from 12 populations in three regions of Xinjiang between 2023 and 2024. The sampling covered 80% of the known range of T. thianschanica in China, as well as the typical habitat of T. iliensis, to ensure ecological representativeness. Four populations were sampled in Tacheng (T. iliensis, 39 individuals), three populations in Urumqi (T. iliensis, 15 individuals), and five populations in the Ili (T. iliensis, 20 individuals; T. thianschanica, 72 individuals). The longitude, latitude, and elevation of each sample were recorded, and a sampling point map of tulip collection sites was created (Figure 1; Table 1).

2.2. Measurement of Major Morphological Traits

From each population, 10 to 15 flowering plants were randomly selected, and their morphological characteristics were measured with tape and an electronic digital caliper (accuracy ±0.01 mm). Their mean values and standard deviations were calculated. The measured phenotypic characters included filamentary shape (FS), coat condition of the stem (SC), pistil length (PL), bulb length (BL) and width (BW), filament/anther length (FA), inside (IL) and outside flower length (OL), inside (IW) and outside flower width (OW), leaf length (LL) and width (LW), aboveground plant height (GH), and total plant height (TH). For the mass trait, if the filament shape is slightly enlarged in the center and gradually narrows towards the ends, it is assigned the value “0”, whereas if the filament shape is suddenly enlarged in the middle and upper part and gradually narrows towards the base, it is assigned the value “1”. For the presence or absence of stem hairs, “0” represents the absence of stem hairs and “1” represents the presence of stem hairs. The data were organized using Excel 2021 V2502 Build 16.0.18526.20168 software and statistically analyzed using one-way ANOVA with Tukey’s post hoc test and descriptive statistics with SPSS R27.0.1.0 [28]. Quartile plots were drawn using Origin V2021 9.8.0 [29].

2.3. Measurements of Karyotype Parameters

We analyzed 14 materials from seven wild tulip species, including T. iliensis, T. thianschanica, Tulipa buhseana, Tulipa schrenkii, Tulipa sinkiangensis, Tulipa patens, and Tulipa altaica. The chromosomal photos of seven wild tulips species were obtained from the relevant research of Liu et al., of which T. iliensis and T. thianschanica were collected from Yamalik Mountain and Zhaosu in Xinjiang, respectively [30]. The metaphase chromosomal cell data of two individuals were collected for each species [31,32,33] according to the Levan classification method [34]. ImageJ 1.31s [35] was used to obtain nuclear data such as short arm (SA), long arm (LA), total relative length (TL = SA + LA), and arm ratio (AR = LA/SA); organize and calculate the data using Excel 2021 software; and finally use Origin V2021 9.8.0 software to make scatter plots of the mean centromeric asymmetry (MCA) and coefficient of chromosome length variation (CVCL) [36,37].

2.4. Phylogenetic Analysis of ITSs

Five individuals were collected per population. Leaves from healthy individuals were collected, dried in silica gel, and stored at −25 °C. Genomic DNA was extracted from the leaves using a DNA Safe Plant Kit (Tiangen Biotechnology, Beijing, China) according to the manufacturer’s instructions. DNA barcoding used ITS 1-4 primers for PCR amplification and the sequencing of the ITS region. An Applied Biosystems Verit96 thermal cycler was used to perform the PCR. All samples were amplified using a 25 µL reaction system, including 1 µL template DNA, 1 µL forward primer (10 µmol/L), 1 µL reverse primer (10 µmol/L), 12.5 μL (5 U/μL) of Premix Taq™, and 9.5 µL ddH2O. The PCR conditions included pre-denaturation at 85 °C for 5 min, followed by 30 cycles of denaturation at 94 °C for 1 min, annealing for 1 min, and extension at 65 °C for 3 min, with a final extension for 5 min at 56 °C. PCR products were detected by 1.5% agarose gel electrophoresis with fluorescent labeling. We selected six samples of T. iliensis and eight samples of T. thianschanica that were successfully amplified and sent them to Sangyo Bioengineering Co. for Sanger sequencing (Supplement note S1). The ITSs of another 111 wild tulip samples and three outgroup samples from the Liliaceae family were downloaded from the National Center for Biotechnology Information (NCBI) database https://www.ncbi.nlm.nih.gov (accessed on 28 February 2025). These sequences were aligned using the ClustalX ver2.1 software and then manually adjusted with the SeAl ver 2.0 software [38,39,40]. MEGA ver11.0.13 software was used to perform multiple sequence alignment and calculate best DNA models, and then the maximum likelihood (ML) best model was used to construct phylogenetic trees [41], with branching support obtained from 1000 bootstrapping replicates [42,43].

2.5. Phylogenetic Tree Mapping of the Chloroplast Genome

A total of 54 tulip chloroplast genome sequences and annotation information were downloaded from the NCBI database. Chloroplast genome sequences were analyzed using multiple sequence alignments in MAFFT v7.505 software [44,45]. Given the similarity of the species sequences, phylogenetic analysis was performed using the maximum likelihood (ML) best model (GTR + F) in TreeBeST 1.9.2 software with a support rating range of (57–100). Developmental trees were beautified using the ITOL online site https://itol.embl.de (accessed on 23 February 2025).

3. Results

3.1. Morphological Comparison

A quantitative analysis of morphological characteristics showed significant differences between T. iliensis and T. thianschanica. Based on box plots and SPSS R27.0.1.0 analysis tables (Figure 2; Supplement Table S1), eight phenotypic traits such as filamentary shape (FS), coat condition of the stem (SC), and pistil length (PL) showed strong taxonomic discriminability (p < 0.001). To make the results more apparent, we tabulated specific data for 14 traits, including the length of the pistil and length and width of the inner and outer flower (Supplement Table S1). The minimum pistil length (PL) of T. iliensis was 0.2 cm and the maximum was 1 cm, while the PL of T. thianschanica ranged from 0.6 cm to 1.4 cm. Figure 2 also indicates significant differences in flower character traits (OL, IL, OW, IW, PL, FS) between T. iliensis and T. thianschanica (p < 0.001). The inner flower width (IW) of T. iliensis (0.7–1.9 cm; 1.21 ± 0.04 cm) and T. thianschanica (0.9–2.4 cm; 1.58 ± 0.06 cm) showed significant differences (p < 0.001). The outer flower width (OW) of T. iliensis (0.5–1.7 cm; 1.03 ± 0.04 cm) and T. thianschanica (0.8–2.4 cm; 1.38 ± 0.13 cm) also differed significantly (p < 0.001). Similarly, T. iliensis and T. thianschanica differed significantly at the level of 0.001 for inner flower length (IL) and outer flower length (OL).

3.2. Karyotyping

Our karyotype data for Tulipa species are based on Liu et al.’s data. The karyotype formulas for T. iliensis and T. thianschanica are 2n = 2x = 24 = 6sm + 18st (3A) and 2n = 2x = 24 = 8sm + 16st (4A), respectively. The individuals are diploids with karyotypes 3A and 4A. All individuals are diploid, with both 3A and 4A karyotypes.
T. iliensis and T. thianschanica share the same chromosome number (2n = 24) but differ in karyotype. Chromosome counts were performed on the chromosome images of T. iliensis and T. thianschanica. The results showed that the number of chromosomes in the cells of both T. iliensis and T. thianschanica was stably 2n = 2x = 24. The average chromosome length and the total length of the chromosome set of T. iliensis and T. thianschanica were measured and calculated. It was found that the average chromosome length range of T. iliensis was 9.87–10.69 μm, and the total length range of the chromosome set was 236.85–256.48 μm (Supplement Table S2). For T. thianschanica, the average chromosome length range was 12.24–13.54 μm, and the total length range of the chromosome set was 293.87–324.97 μm. T. iliensis and T. thianschanica exhibited significantly different chromosome length characteristics.
T. iliensis and T. thianschanica have the same chromosome number (2n = 24), but there are differences in their karyotype and molecular formula. By constructing a scatter plot of MCA and CVCL, the aim is to visually present the distribution pattern of T. iliensis and T. thianschanica in the multivariate chromosomal karyotype feature space and the visual assessment of classification accuracy (Figure 3). In the scatter plot of MCA and CVCL, T. thianschanica and T. iliensis are clearly divided into upper and lower parts (T. iliensis: MCA scope: 75–77, CVCL scope: 16–17; T. thianschanica: MCA scope: 75–76, CVCL scope: 22–23). The samples of T. thianschanica are concentrated in the upper area, while the samples of T. iliensis are mainly located in the lower area. This distribution pattern provides an intuitive and crucial basis for the effective differentiation between the two, and the results indicate that T. iliensis and T. thianschanica are different species.
Based on the above results of the chromosomal karyotype analysis of T. iliensis and T. thianschanica, the two tulips can be clearly classified into different karyotypic categories, which provides a solid cytological basis for their taxonomic identification and lays a foundation for the further exploration of their evolutionary relationships and genetic diversity.

3.3. Molecular Phylogeny

In the phylogenetic tree constructed based on the ITSs, all samples of T. iliensis formed a monophyletic branch (94% bootstrap support), indicating its obvious genetic consistency and uniqueness at the ITS level (Figure 4). This branch showed a clear differentiation from the branch of T. thianschanica. The samples of T. thianschanica also formed a relatively independent branch (97% bootstrap support). In comparison with other Tulipa species, the relative positions of T. iliensis, T. thianschanica, and Tulipa suaveolens on the phylogenetic tree suggested that there might be relatively close genetic relationships among them (75% bootstrap support), yet T. iliensis could still be clearly distinguished from T. thianschanica (84% bootstrap support).
In the phylogenetic tree constructed based on the chloroplast whole genome, the topological structure of the phylogenetic tree clearly shows the phylogenetic positions of the samples of T. iliensis and T. thianschanica (Figure 5). Among them, some samples of T. iliensis and T. thianschanica are in close proximity to each other (OL 350838/NC 061964 and MW077740), and these adjacent samples form relatively compact clustering branches (100% bootstrap support). They are closely connected on the phylogenetic tree, indicating that the genetic differences at the chloroplast whole genome level are relatively small. This might imply that there are relatively frequent gene exchanges in these specific populations. However, at the same time, there are also cases where some samples of T. iliensis and T. thianschanica are far apart in the phylogenetic tree (NC 052697/MT316023 and OL 350838/NC 061964). These distantly located samples are distributed on different branches of the phylogenetic tree, meaning that they have accumulated more variations in the chloroplast whole genome sequences.
Based on the results of both the ITS and chloroplast whole genome phylogenetic trees, it can be clearly identified that T. iliensis and T. thianschanica are two independent species with obvious genetic differences. They each have unique genetic characteristics at the molecular level and also have different degrees of genetic relationship differences with other Tulipa species. This provides an important molecular basis for the taxonomic research and species identification of Tulipa plants.

4. Discussion

Plant taxonomy is the cornerstone of biodiversity research, and in the case of the genus Tulipa, it helps us identify and differentiate between species, determine which are at risk of extinction, and prioritize conservation measures [46,47,48,49,50]. Modern taxonomy methods have evolved from using single morphological features to incorporating genomic, molecular, cytological, genetic, geographical, and morphological data. In the case of T. iliensis and T. thianschanica, our integrative approach combining morphological, karyotypic, and molecular evidence robustly supports their classification as distinct species, resolving historical ambiguities in their identification.
We found that T. iliensis and T. thianschanica differed significantly in the phenotypic traits of filament shape, pistil length, the presence or absence of stem hairs, whole plant height, and internal and external flower length and width, supporting the conclusion that they are two distinct species. These morphological differences may be important for species evolution or ecological adaptation [51,52,53]. For example, plants with short pistils may favor self-pollination, shorten the growth distance of pollen tubes, accelerate the reproductive process, reproduce rapidly to increase the number of individuals, and favor the occupation of ecological niches. It is noteworthy that the pistil length of T. iliensis was shorter than that of T. thianschanica (T. iliensis: 0.66 ± 0.03; T. thianschanica: 0.96 ± 0.03; p < 0.001), a trait that may be related to the efficiency of self-pollination and the rapid colonization of ecological niches. These findings are consistent with those of Zhou and Rosas et al., who both emphasized the use of flower morphology to delimit species [54,55]. However, our study further identifies the absence of stem hairs in T. iliensis, which is distributed in Yili, as a trait subject to revision, which contradicts earlier descriptions in Flora. This highlights the need for field-based trait validation in dynamic environments. Therefore, during the outdoor survey, we suggest that filament shape combined with whole plant height and perianth and pistil size are the key distinguishing characters for identifying the two tulip species in the Ili region. Outside of Ili, for more accurate classification, we suggest the combination of filament shape and stem hairs as the phenotypic characters for identifying T. iliensis. Compared with previous studies [13], the present study not only verified some of the differences found, but also revised and added some new distinguishing traits, which further clarify the morphological differences between the two species and provide a more comprehensive morphological basis for species classification.
Karyotype analysis, involving chromosome number and morphology, is a common method in cytological studies that reveals taxonomic and phylogenetic relationships. Closely related species often have similar chromosome numbers and morphologies [56]. T. iliensis and T. thianschanica share the same chromosome number (2n = 24) but differ in karyotype. Previous studies have indicated that T. iliensis and T. thianschanica have different karyotypes [30]. Our analysis used scatterplots for polymorphic chromosome analysis (MCA) and chromosome variation length coefficient (CVCL) to highlight the differences between the two species (Figure 3). The distinct karyotypic characteristics support the classification of these two tulips as separate species within the same genus. In this study, the karyotypic differences between T. iliensis and T. thianschanica are phylogenetically significant. Compared with closely related species such as T. schrenkii, their differences in chromosome length and arm ratio imply that they undergo unique chromosome structural variations such as inversions and translocations in their evolution, which drive species differentiation and clarify the branching positions of their evolutionary trees, which helps to understand the evolutionary lineage of the whole genus.
Molecular evidence, including ITS and chloroplast genome analysis, also supported the distinction between these species. The ITS region evolves rapidly, has small length variations, and contains numerous mutation sites, making it effective for distinguishing species [57,58]. Phylogenetic analyses of ITSs and chloroplast genomes strongly distinguish these two species (Figure 4 and Figure 5). However, topological inconsistencies between their trees suggest that shared haplotypes in sympatric populations evidence historical hybridization [59,60]. This has had a profound impact on the genetic characterization, evolutionary direction, and taxonomic status of T. iliensis and T. thianschanica [61,62]. Hybridization has resulted in the sharing and exchange of some genes between the two species, and this gene flow may explain the overlapping morphological traits, resulting in genetic uniqueness and some similarities, while maintaining species-specific adaptations that account for phenotypic similarities [63]. In terms of evolutionary direction, the introduction of new combinations of genes by hybridization may provide the raw material for the generation of new traits, such as certain physiological traits adapted to specific environments, giving them more evolutionary possibilities in the face of environmental change [64,65]. Chloroplast genomes are inherited maternally and are particularly useful for studying evolutionary history, whereas ITSs are more effective for studying relationships at the subspecies level. The combination of the two reveals the genetic relationships between T. iliensis and T. thianschanica at different levels and perspectives, compensating for the limitations of single molecular marker studies. Our study revealed genetic hybridization and distributional overlap between T. iliensis and T. thianschanica, which may explain their phenotypic similarity and previous difficulties in distinguishing them.
In 2021, tulips were added to the “List of National Key Protected Wild Plants” due to their economic and ecological value and their declining populations resulting from habitat destruction and human activities [66]. Proper identification and classification provide a scientific basis for the prioritization of conservation efforts. T. iliensis has a wider distribution and greater habitat variation, but is classified as Near Threatened on the IUCN Red List, mainly due to human disturbance and illegal collection [67,68,69]. T. thianschanica is even more vulnerable due to its small population size and limited distribution in the Ili region. Both species face human interference due to their medicinal and edible value. In addition to establishing nature reserves and promoting education, we recommend using molecular genetic markers to assess the genetic diversity and differentiation of populations, and to develop scientific and effective conservation strategies for these two tulip species.

5. Conclusions

This study comprehensively employed phenotypic, karyotypic, and molecular marker techniques to conduct in-depth research on T. iliensis and T. thianschanica of the genus Tulipa in Xinjiang. Phenotypic classification research accurately identified characteristics such as filament shape as the key phenotypic traits for distinguishing these two wild tulip species. Based on the karyotype classification results of the MCA and CVCL scatter plots, it was clearly defined that T. iliensis and T. thianschanica belong to different karyotypes. Through a comparative analysis of the phylogenetic trees of ITSs and the complete chloroplast genome, it was conclusively revealed that there is a hybridization phenomenon between the two. This study has laid a solid foundation for the research on the biodiversity of wild tulips and the promotion of the sustainable development of species. It has clarified the positions of T. iliensis and T. thianschanica in the classification system, providing crucial theoretical support and technical approaches for subsequent in-depth research, long-term protection, and the rational development and utilization of resources related to these two species. Below we officially consider T. iliensis and T. thianschanica as two separate species within the genus Tulipa, with a minor revision of the description of the two tulips in the Flora of China [70].

6. Taxonomic Treatment

  • Tulipa iliensis Regel in Gartenfl. 28: 162, 1879; Vved. in F1. URSS 4: 347. 1935, Hall, Gen. Tulipa 136. 1940; Atlas of higher plants in China 5: 445, t. 7719. 1976. Flora of China 14: 91, 1980; Desert Flora of China 1: 221, 1985.
The plant is usually 10–30 cm tall. Bulb oval, 2–2.5 cm in diameter, bulb skin dark brown, thin leathery, outer glabrous, and inner, upper, and base with voracious hairs. Stems usually hairy or hairless. Leaves 3–4, strip or strip lanceolate, generally 0.5–1.5 cm wide, spaced apart or adjacent to each other but nearly whorled, extended, or recurved, and margins flattened or microwavy. Flowers often single terminal, yellow; perianth 25–35 mm long, 4–20 mm wide; outer perianth segments elliptically rhomboid, back with greenish-purple, purple-green, or yellow-green color; inner perianth segments long obovate, yellow. When the flowers die, they usually become darker, dark red, or reddish yellow; 6 stamens equal in length; filaments hairless, slightly enlarged in the middle, and gradually narrowed to both ends; ovary rectangular round, rarely stylous, usually 0.4–1 cm. Capsule oval, 15–25 mm long; seeds flattened, subtriangular.
Phenology. Flowering in April to May, fruit in May.
Distribution and habitat. Along the north slope of the Tianshan Mountains in Xinjiang, it is widely distributed from Urumqi, Manas, Shawan, and Jinghe in the east to the counties of the Yili region in the west. Born at an altitude of 400–1200 m in the piedmont plain, low slope, hillside grassland, Gobi, roadside, often into a large area of growth. It is also found in Russia and Central Asia.
2.
Tulipa thianschanica Regel in Act. Hort. Petrop. 6: 503. 1880; et 8: t. 5. 1884; Vved. in F1. URSS 4: 349. 1935; ФJI.Кaзax. 2: 208. 1958; Flora of China 14: 91, 1980.
This species is similar in morphology to T. iliensis; the main differences are as follows: The middle and upper parts of filaments widen almost suddenly, and gradually narrow toward the base. Stems glabrous. The whole plant height is high, about 12–45 cm. The length and width of the petals are larger, that is, the flower is larger. The pistil is relatively long. The leaves are closely arranged and the leaves are recurved.
Phenology. Flowering May to June. Fruit in June.
Distribution and habitat. It is found only in western Xinjiang, Xinyuan, Qapqal, Tokkuzur, Zhaosu, etc. Born in the mountain grassland area at 1000–1800 m above sea level; It is also found in Soviet Central Asia.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/d17030219/s1. Table S1: Results of SPSS analysis of phenotypic data 2.27; Table S2: Chromosomal data result table.

Author Contributions

H.Z. for plant survey, data compilation and analysis, article conceptualization, and first draft writing; X.W. for funding acquisition and article writing—review and editing; H.L. for funding acquisition and project management; S.L. for plant survey and software acquisition; Y.W. for conceptualization and article review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This study was Suppported by the Chinese Academy of Sciences (2022xjkk0801), the conservation and molecular breeding of characteristic forest fruit germplasm resources in Xinjiang (E435012001) and the Chinese Academy of Sciences (None) and China-Kazakhstan Partnership Research Institute (E4600108).

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Distribution map of T. iliensis and T. thianschanica collection areas. Populations 1–10: T. iliensis; Populations 10–13: T. thianschanica.
Figure 1. Distribution map of T. iliensis and T. thianschanica collection areas. Populations 1–10: T. iliensis; Populations 10–13: T. thianschanica.
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Figure 2. Variation in key taxonomic characters, including outer flower length, inner flower length, outside width, inside width, total height, filamentary shape, stem coat condition, and pistil length, in different populations of Tulipa (T. iliensis: 9 populations; T. thianschanica: 3 populations). Note: Small squares are mean values, and small diamonds are outliers.
Figure 2. Variation in key taxonomic characters, including outer flower length, inner flower length, outside width, inside width, total height, filamentary shape, stem coat condition, and pistil length, in different populations of Tulipa (T. iliensis: 9 populations; T. thianschanica: 3 populations). Note: Small squares are mean values, and small diamonds are outliers.
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Figure 3. Scatterplot of MCA and CVCL for T. iliensis, T. thianschanica, and other wild tulips from Xinjiang (T. buhseana, T. schrenkii, T. sinkiangensis, T. patens, and T. altaica). Note: MCA is the horizontal axis and CVCL is the vertical axis. The green circle represents T. iliensis and the red triangle represents T. thianschanica.
Figure 3. Scatterplot of MCA and CVCL for T. iliensis, T. thianschanica, and other wild tulips from Xinjiang (T. buhseana, T. schrenkii, T. sinkiangensis, T. patens, and T. altaica). Note: MCA is the horizontal axis and CVCL is the vertical axis. The green circle represents T. iliensis and the red triangle represents T. thianschanica.
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Figure 4. The majority rule consensus tree based on ITSs for T. iliensis Regel, T. thianschanica Regel, and other related species in GenBank. Remarks: Marked in red is T. iliensis, and marked in blue is T. thianschanica.
Figure 4. The majority rule consensus tree based on ITSs for T. iliensis Regel, T. thianschanica Regel, and other related species in GenBank. Remarks: Marked in red is T. iliensis, and marked in blue is T. thianschanica.
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Figure 5. Phylogenetic tree of 54 chloroplast genomes of T. iliensis Regel, T. thianschanica Regel, and other wild tulips. Remarks: Marked in red is T. iliensis, and marked in blue is T. thianschanica.
Figure 5. Phylogenetic tree of 54 chloroplast genomes of T. iliensis Regel, T. thianschanica Regel, and other wild tulips. Remarks: Marked in red is T. iliensis, and marked in blue is T. thianschanica.
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Table 1. Population information of T. iliensis and T. thianschanica.
Table 1. Population information of T. iliensis and T. thianschanica.
Pop. N.SpeciesLocationLatitudeLongitudeElevation
1T. thianschanicaQapqal Xibe Autonomous County S23743.50° N81.12° E1737 m
2T. thianschanicaTokkuzkuzur County G57743.37° N81.88° E1551 m
3T. thianschanica, T. iliensisSenmatas village, Kashagar town, Zhaosu County42.84° N81.08° E1713 m
4T. iliensisBaibird Lake, Urumqi City43.83° N87.44° E768 m
5T. iliensisUrumqi small green valley43.84° N87.50° E798 m
6T. iliensisUrumqi Yamalik Mountain43.80° N87.58° E863 m
7T. iliensisAlemale town, Xinyuan County43.60° N81.24° E1155 m
8T. iliensisArtificial forest of dolomite mine in Xinyuan County43.38° N83.56° E2697 m
9T. iliensisYangpo of dolomite mine in Xinyuan County43.41° N83.58° E1255 m
10T. iliensisEmin county wild fruit forest scenic spot46.69° N84.72° E938 m
11T. iliensisShawan City cattle circle ranch43.93° N85.70° E1181 m
12T. iliensisYumin County Baluk Mountain scenic spot45.84° N82.56° E1673 m
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Zhang, H.; Wang, X.; Liu, H.; Liu, S.; Wei, Y. Clarifying the Taxonomic Relationships of Tulipa iliensis and T. thianschanica Based on Multiple Evidences of Phenotypic, Karyotype, Molecular, and Chloroplast Genomes. Diversity 2025, 17, 219. https://doi.org/10.3390/d17030219

AMA Style

Zhang H, Wang X, Liu H, Liu S, Wei Y. Clarifying the Taxonomic Relationships of Tulipa iliensis and T. thianschanica Based on Multiple Evidences of Phenotypic, Karyotype, Molecular, and Chloroplast Genomes. Diversity. 2025; 17(3):219. https://doi.org/10.3390/d17030219

Chicago/Turabian Style

Zhang, Huimin, Xiyong Wang, Huawei Liu, Shiqing Liu, and Yan Wei. 2025. "Clarifying the Taxonomic Relationships of Tulipa iliensis and T. thianschanica Based on Multiple Evidences of Phenotypic, Karyotype, Molecular, and Chloroplast Genomes" Diversity 17, no. 3: 219. https://doi.org/10.3390/d17030219

APA Style

Zhang, H., Wang, X., Liu, H., Liu, S., & Wei, Y. (2025). Clarifying the Taxonomic Relationships of Tulipa iliensis and T. thianschanica Based on Multiple Evidences of Phenotypic, Karyotype, Molecular, and Chloroplast Genomes. Diversity, 17(3), 219. https://doi.org/10.3390/d17030219

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