Phylogeny of Siberian species of Carex sect. Vesicariae based on nuclear and plastid markers

Carex sect. Vesicariae is a group of about 30 sedge species widespread in temperate and cold regions of Eurasia and North America. In this study we performed a phylogenetic analysis of ten taxa (9 species and one subspecies) found in Siberia based on two plastid sequences (matK and atpF-H) and the nuclear ribosomal ITS2 sequence. We also developed a novel sequence marker for the genus Carex, an intron of the nuclear hsp90 gene, which was found to be several times more variable than plastid and nuclear ribosomal sequences. Total nucleotide variation within the Vesicariae section was found to be very low, comparable to that within single other sedge species. Phylogenetic analysis supported the existence of two groups within this section: clade A (C. vesicata, C. vesicaria, both subspecies of C. saxatilis and C. pamirica) and clade B (C. rostrata, C. mollissima, C. jacutica, C. rotundata and C. membranacea). Carex rhynchophysa holds an intermediate position between these groups. The main morphological difference between these clades lies in the nature of the transition of the utricle into the beak: it is gradual in clade A and abrupt in clade B. This division is in good accordance with the results of previous allozyme studies and with current taxonomy. These results may become the basis for consideration of subsectional taxa within this section.