Morphology, Taxonomy, Geographic Distribution, Genetic Diversity, and Phylogenomics of the Genus Tulipa L.: A...

The genus Tulipa L. is a common group of ornamental plants, characterized by high morphological variability and a complex taxonomy. Despite considerable interest in this group, assessments of its species composition remain inconclusive, as evidenced by discrepancies between contemporary taxonomic sources. The number of recognized taxa varies across major taxonomic databases, including Plants of the World Online, World Flora Online, and Euro+Med PlantBase, reflecting ongoing taxonomic revisions and differences in species concepts. In terms of distribution patterns, 7.6% are widely distributed taxa across transcontinental regions, 28.0% occur across multiple countries within a continent, and 66.9% are range-restricted taxa. The latter group includes 4.2% transnational endemics, 44.1% single-country endemics, 8.5% single-region endemics, and 10.2% single-site endemics. Recent taxonomic and evolutionary studies of Tulipa increasingly rely on molecular approaches, particularly DNA barcoding and chloroplast genome analyses, which have improved phylogenetic resolution and species delimitation in several cases. However, truly comprehensive studies combining morphological, cytogenetic, and molecular datasets remain limited and are typically restricted to individual taxa or species complexes rather than the genus as a whole. Modern molecular genetic studies demonstrate the high informativeness of both nuclear and plastid markers for studying the phylogeny, systematics, and genetic diversity of Tulipa species. Natural populations of Tulipa are under pressure from anthropogenic factors and climate change, resulting in reduced range and habitat degradation. According to the International Union for Conservation of Nature Red List of Threatened Species, among 118 taxa of the genus Tulipa, T. sprengeri Baker is classified as Extinct in the Wild, 5.9% as Critically Endangered, 5.9% as Endangered, 8.5% as Vulnerable, 11.9% as Near Threatened, and 11.0% as Least Concern. The use of exclusively national assessments to determine species extinction risk may be insufficiently objective, whereas global assessments provide a more informative and reliable approach for evaluating conservation status. In this review, we combine investigations of the morphology, taxonomy, and geographic diversity; population genetic structure and molecular diversity; and molecular phylogenetics and plastome-based genomics of the genus Tulipa. Furthermore, the review examines current challenges and future research prospects, emphasizing that studies of the genus Tulipa should integrate morphological, genomic, and ecological approaches to refine taxonomy and conserve genetic resources.