An unexpected new diploid Hieracium from Europe: Integrative taxonomic approach with a phylogeny of diploid Hieracium taxa

Abstract

Hieracium s.str. (Asteraceae) is one of the largest angiosperm genera notorious for its taxonomic complexity caused by widespread interspecific hybridization. This process is tightly coupled with polyploidization and apomixis – asexual reproduction by seeds, which has ensured the persistence of otherwise sterile interspecific hybrids. As a result, apomictic polyploid taxa dominate the taxonomic diversity of the genus whilst sexual diploid species are extremely rare and mostly confined to southern Europe. As diploid taxa are assumed to be the parents of apomictic lineages, the discovery of any new diploid species is important for understanding evolutionary processes and diversity patterns in the genus. Here, we describe a new diploid species, Hieracium vranceae, a narrow endemic to the Munţii Vrancei (Vrancea Mountains, Eastern Carpathians, Romania). This taxon with a distinctive morphology and a strong affinity to relic rocky habitats was first collected in 2013. This means that, even in Europe, some regions, like the Eastern Carpathians, are botanically underexplored and might still preserve an undiscovered diversity of plants. Phylogenetic analyses with multiple molecular markers (low‐copy nuclear genes gsh1 and sqs, nuclear ribosomal ETS, four cpDNA loci) applied to all diploid Hieracium species support specific rank for H. vranceae. In contrast, molecular data suggest conspecifity of two pairs of species, H. lucidum/H. cophanense from Sicily and H. naegelianum/H. renatae from the Balkans, which are moreover only weakly differentiated morphologically. Molecular (cpDNA) and cytogenetic (GISH, FISH) analyses furthermore revealed that H. vranceae has been involved as a maternal parent in the origin of an allotriploid apomictic species, H. telekianum, to which H. vranceae contributed one haplome. The other putative parents of H. telekianum are the diploid narrow endemic H. pojoritense and probably H. sparsum s.l. Our data thus stress the importance of interspecific hybridization for an evolutionary shift from sexuality to apomixis in Hieracium. Our findings furthermore highlight the significance of that part of the Carpathians as one of the most important evolutionary/refugial centres of Hieracium and suggest dynamic species ranges at a regional scale allowing physical contact of taxa whose distributional ranges are nowadays completely allopatric.

A Multigene Phylogeny of Native American Hawkweeds (Hieracium Subgen. Chionoracium, Cichorieae, Asteraceae): Origin, Speciation Patterns, and Migration Routes

“…Altogether, we apply seven distinct markers, five of them unlinked: plastid trnT-trnL and trnV-ndhC , nuclear ribosomal ITS , ETS and 5S-NTS , and parts of the low-copy nuclear genes sqs and gsh1 [ 34 ]. In different groups of the Hieraciinae and in various combinations, they revealed particular aspects of speciation [ 25 , 26 , 43 , 44 , 45 , 46 , 47 ]. The majority of these markers is highly variable in the study group and consists mostly of non-coding DNA (intergenic spacers, introns).…”

Karyotype and genome size variation in white-flowered Eranthis sect. Shibateranthis (Ranunculaceae)

“…Differences and similarities in karyotypes between taxa may reflect their evolutionary relationship (Shubert 2007;Peruzzi et al 2009;Escudero et al 2014;Baltisberger and Hörandl 2016). At present, it is appropriate to use the comparative analysis of karyotypes as part of an integrative approach to solving the issues of systematics and phylogeny (Astuti et al 2017;Mráz et al 2019;Erst et al 2020b).…”

Typification of fourteen Linnaean names in the genus Hieracium (Compositae)

“…Hieracium L. (Compositae) is one of the most taxonomically complicated genera of vascular plants in the temperate flora (Kilian & al., 2009; Mráz & al., 2019; Chrtek & al., 2020), and its taxonomic treatments vary in different parts of Europe, e.g., the Central European school of “hieraciology” (species are divided into subspecies, varieties, etc.) vs. Scandinavian, British and Russian botanists (all morphologically recognizable forms are treated at species rank; “microspecies”) (Grisebach, 1853; Nägeli & Peter, 1886; Zahn, 1921–1923, 1930; Pugsley, 1948; Sell & West, 1976; Lack, 1977; Schljakov, 1989; Schuhwerk, 2002; Sennikov, 2002, 2003; Zidorn & al., 2002; Frodin, 2004; Greuter, 2007; Greuter & Raab‐Straube, 2008; Mateo & Egido, 2017; Mateo & al., 2017).…”