Introduction
Species of the genus Tulipa L. (Liliaceae) have great economic, horticultural, esthetical, ecological, conservational and taxonomic importance (Veldkamp and Zonneveld, 2012). They are bulbous monocots, characterized by a high variability of vegetative and floral characters which were traditionally used to characterize species. Furthermore, the vegetative and floral characters appear to be plastic (polythetic), sometimes even within populations of a species (Christenhusz et al., 2013; Zonneveld and de Groot, 2012). Because of that, the taxonomy of this genus is considered to be difficult, despite the existence of a large body of literature (Eker et al., 2014; Zonneveld, 2009; Zonneveld and de Groot, 2012). Taking that into consideration, the classification of Tulipa has been revised several times (Turktas et al., 2013). The total number of Tulipa species still is not exactly defined and ranges from 40-150 species according to various researchers (Eker et al., 2014). In the World Checklist of Selected Plant Families(Govaerts, 2019), 516 names have been listed for Tulipa , but only 102 taxa have been accepted, while in the Plant List (“The Plant List,” 2013) 499 names have been listed for Tulipa and 120 taxa have been accepted. According to Christenhusz et al . (2013) only 76 species are accepted. The number of Tulipa species native to the Balkan Peninsula is much less, varying from 15 (Hayek 1933) to 22 (Govaerts 2010). In Kosovo the genus Tulipa is represented by eight taxa (six species and two subspecies), belonging to the two subgenera Eriostemones and Tulipa, respectively. The subgenus Eriostemones is represented by T. sylvestris , which is represented by two subspecies, Tulipa sylvestris subsp.australis (Link) Pamp (accepted subsp.) and Tulipa sylvestris subsp. sylvestris only accepted by the World Checklist of Selected Plant Families (Govaerts, 2019). In Kosovo the subgenus Tulipa is represented by several species: Tulipa gesneriana L., Sp. Pl.: 306 (1753) (Millaku et al., 2018) has a hybrid origin derived from T. agenensis, T. armena, T. suaveolens and others (Govaerts, 2019). Tulipa scardica Bornm. is distributed in Southern Kosovo and Macedonia (Mayer and Micevski, 1970). In Kosovo, it is present near the village Krivenik, close to the border of Macedonia. It is synonymized asTulipa gesneriana L. (“The Plant List,” 2013; Zonneveld, 2016), accepted as a species by the World Checklist of Selected Plant Families(Govaerts, 2019), but not accepted by Flora Eurepea (Tutin et al. 1980).Tulipa serbica Tatic & Krivošej is distributed on serpentine soil in the South of Serbia (community Knjaževac: Mt. Rogozna near Donja Kamenica) and Northern Kosovo (Beli Laz hill, near Ibar river) (Tatić and Krivošej, 1997). Tulipa kosovarica Kit Tan, Shuka & Krasniqi is distributed in Kosovo, in the serpentine area of Mirusha region at the foot of Mt. Kozniku, between Mrasori and Llapçevë villages (Shuka et al. 2012), as well as in the localities Guriç, Llapushnik, Qafë – Prush and Devë (Millaku et al., 2018). Tulipa luanica Millaku is distributed on limestone substrate on Mt. Pashtriku which is located in the district of Prizren, Southern Kosovo near the border with Albania (Millaku and Elezaj, 2015). Tulipa albanica Kit Tan & Shuka was the first time described as a new species from Albania (Kukësi district: from Kolshi to Surroj village, on serpentine slopes) (Shuka et al., 2010), but was recently found in the Kosovar village of Deva too (Millaku et al., 2018). Tulipa scardica, T. serbica, T. albanica, T. kosovarica and T. luanica belong to the T. scardicacomplex (Christenhusz et al., 2013) and share many similar morphological features (Shuka et al., 2010; Shuka and Tan Kit, 2012; Tatić and Krivošej, 1997). Because of their similarities, these species sometimes have been synonymized, erroneously identified or misclassified.
To study the taxonomy and relationships of these species, mainly their morphological characteristics and their geographical distribution has been used. Additionally, karyological analyses for T. albanica,(Shuka et al., 2010) and T. luanica (Millaku and Elezaj, 2015), as well as nuclear genome size (DNA 2C-values) for T. albanica,(Osmani, 2018; Shuka et al., 2010), T. scardica (Zonneveld, 2009), T. kosovarica and T. luanica (Osmani, 2018) have been used. However, DNA content and cytogenetic analyses are not known for all of the species present in Kosovo in order to provide information about species relationships.
DNA barcoding is a techniques, which has emerged in the last decades as powerful tool in plant systematics and became important as an inexpensive and reliable technique for phylogenetic studies (Kress, 2017). Molecular phylogenetic analysis using sequences from nuclear ribosomal DNA (nrDNA) and chloroplast DNA (cpDNA) was successfully used for phylogenetic analysis of the genus Tulipa . Thus,Tulipa DNA sequences from the ITS region (Christenhusz et al., 2013; Fay et al., 2006; Turktas et al., 2013; Yanagisawa et al., 2012) and the trnL-trnF region (Peterson et al., 2008) were used for phylogenetic analyses.
This work aimed to determine the phylogenetic relationships of wild-growing Tulipa species of Kosovo, employing the plastidtrnL-trnF and nuclear ITS region. To the best of our knowledge, up to now no studies addressing this DNA barcodes for the KosovarTulipa species were reported.