Phylogenetics of blackberries (Rubus; Rosaceae) and new evidence of hybridization involving R. ursinus.
Inferring the phylogenetic relationships in Rubus (Rosaceae) have been a challenge and particularly within subgenus Rubus (blackberries, dewberries). To improve resolution and support within this group, we added sequences from the chloroplast DNA trnS-trnG spacer and trnG intron to existing data bringing our total to approximately 6700 aligned characters. Our parsimony results suggest that subgenus Rubus species, excluding putative allopolyploids involving other subgenera, are monophyletic and form three unresolved lineages: New World, European, and an odd assemblage comprising R. ursinus, eastern North American R. flagellaris (9x), and European R. caesius (4x). The New World clade is divided into strongly supported North American and Central/South American subclades. Due to limited variation in the chloroplast genome, we will include more noncoding cpDNA sequences in subsequent analyses. A second notable finding is that R. ursinus is hybridizing with introduced blackberry species in California based on nuclear ITS region sequences. We have detected putative hybrids between R. ursinus and Eurasian R. armeniacus (Himalaya berry) as well as R. ursinus and eastern North American R. pensilvanicus; both are presumed tetraploids. In each case, R. ursinus has been the maternal parent. This undoubtedly complicates the systematics of this species and may have significant implications to habitat restoration where R. ursinus is used.
