Cytological characterization of three closely related pines - Pinus mugo, P. uliginosa and P. x rhaetica from the Pinus mugo complex (Pinaceae)

The Pinus mugo complex comprises closely related pines in different taxonomic ranks, which commonly occur in major European mountain chains. This large and polymorphic complex has been, and still is, a considerable challenge for taxonomists due to highly variable phenotypical characteristics within particular taxa, ongoing hybridization in sympatric populations, lack of distinct morphological species-specific determinants, and the absence of distinct genetic differentiation among them. Moreover, cytogenetic data on pines from this complex are very scarce. Therefore, in this study, we used C-banding methods and flow cytometric analysis in order to provide new data on karyotypical features and DNA content of three closely-related pines from the Pinus mugo complex, i.e., Pinus mugo (Turra), Pinus uliginosa (Neumann), and Pinus x rhaetica (Brugger) and to gain more insight into the taxonomic relationships between these pines. Our results confirmed that the basic number of chromosome is the same amongst the analyzed taxa (2n=2x=24), and that the karyotypes have a similar morphology. The number of secondary constrictions (SCs) and C-banding patterns differed slightly between P. mugo, P. uliginosa and P. x rhaetica. The nuclear DNA content (2C/pg) among analyzed taxa is from 46.41pg for P. mugo and P. x rhaetica to 46.48pg for P. uliginosa. For each of these pines, certain taxa-specific cytogenetic determinants were identified. Our results indicate that they may represent two different taxa, and so their names should not be used interchangeably in scientific literature.