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Phylogeography and genetic diversity of endemic Centaurea ragusina L. (Asteraceae) from Dalmatia

Centaurea ragusina L. (Asteraceae) is a Dalmatian narrow endemic species that grows as typical chasmophyte mostly on inaccessible vertical sea cliffs. It’s represented by two subspecies: typical C. ragusina subsp. ragusina with pinnatifid basal leaves which is distributed from north to south Dalmatia (Dugi Island to Konavle), while C. ragusina subsp. lungensis has mainly entire basal leaves, present only on the islands of Dugi and Kornati archipelago. We used amplified fragment length polymorphisms (AFLPs) to access the genetic diversity, differentiation and structure of populations across its entire distribution range (on 210 individuals from 22 populations). The aims were to test taxonomic validity of existence of two subspecies, to investigate genetic structure, to search for variations in the cpDNA sequences using trnL-trnF and rpL32-trnL markers and to quantify the genetic diversity within and among populations of C. ragusina. The results obtained from analyses of molecular variance (AMOVA) showed that 36.09% of genetic variation can be attributed to differences among populations. Mantel test revealed positive correlation between genetic and geographical distance between pairs of populations. Our study implies that most previous taxonomic infra- specific concepts of C. ragusina were artificial and according to results obtained by BAPS and STRUCTURE there is no clear genetic evidence that support existence of subsp. lungensis as a separate taxon from typical subsp. ragusina. On total of 60 samples, 16 different chloroplast haplotypes were detected. Haplotypes network indicate very fragmented distribution of C. ragusina that can be consequence of evolutionary history and colonization of vertical rocky cliffs during the Pleistocene sea level changes. Recommendations for conservation purposes of C. ragusina based on the patterns of genetic diversity were proposed.

genetic diversity; AFLP; phylogeography; Centaurea ragusina; conservation genetics

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