Phylogenetics of Rubus ursinus and R. macraai (Rosaceae): Evidence of hybrid origin

摘要

This study had three goals: elucidating the affinity between Rubus ursin us and Rubus macraei, assessing the hybrid origin of both species, and determining closely related species that may be putative parents. To this end, three chloroplast DNA regions-rp1l6, trnK, trnL-tmF-and two nuclear DNA regions-the ribosomal internal transcribed spacer (ITS) and granule-bound starch synthase (GBSSI)-were sequenced for five R. ursinus individuals, including 6x, 8x, l lx, 12x, and 13x ploidy levels, and R. macraei, which is hexaploid. Sequence data were placed into an existing framework of a Rubus phylogeny. Three phylogenies were created that demonstrate a close association between R. ursinus and R. macraei, but place both ofthese species in disparate clades. Chloroplast data strongly support a sister group relationship between all five accessions of R. ursinus and both accessions ofR. macraei. This clade is one lineage in a trichotomy including European and New World blackberries, species in subgenus (subg.) Rubus. ITS region sequences place both species in a weakly supported clade containing largely subg. Idaeobatus species. GBSSI data place clones ofR. ursinus and R. macraei in two wellsupported yet disparate clades with either subg. Rubus or subg. Idaeobatus species. These results support a previous suggestion of an allopolyploid origin ofR. ursinus by providing phylogenetic evidence from multiple markers in the same study, and represent the first observance of polymorphism in Rubus macraei that indicates an allopolyploid origin. Closely related species include not only members of subgenera Rubus and Idaeobatus but also R. nivalis of subg. Chamaebatus. This study represents the first evidence of a possible role of a species outside subgenera Rubus or Idaeobatus in origin of R. ursinus and R. macraei.