Molecular phylogenetic systematics of Rubus (Rosaceae)

Rubus is one of the most challenging genera of plants regarding classification and identification. The genus includes approximately 750 species found on all continents except Antarctica and is important economically and ecologically. This thesis involves the use of molecular evolutionary data in three independent studies to improve our understanding of classification in Rubus.; I sequenced the nuclear ribosomal DNA (nrDNA) internal transcribed spacer region (ITS 1-5.8S - ITS 2; ITS) of 56 Rubus species plus Dalibarda to infer evolutionary relationships in this group and to compare the implications of these results for Rubus classification with those of previous workers. My results indicate that Rubus and most of its subgenera are unacceptable because they do not have a unique history, although, some groups are strongly supported. Traditionally important characters of leaf type and stem armature are highly variable and not good indicators of relationship in Rubus. The data also suggest that Rubus did not originate in China as previously hypothesized.; I also studied a case of hybridization between species of two subgenera, R. caesius (European blackberry) and R. idaeus (red raspberry) using ITS sequences and restriction site analysis to test this hypothesis and to determine whether the hybrids themselves have reproduced. My results confirm the hybrid origin of seven sampled plants and indicate that most have reproduced generating complex patterns.; Third, I assessed the evolutionary utility of the nuclear gene waxy, which has only been used in one other evolutionary study I know of and yet, holds great promise in this area. Waxy is an alternative source of evolutionary data more discriminating than ITS for closely related species of Rubus and not hindered by limitations of other genes. My data suggest that waxy gene introns are informative within genera and waxy exons are informative among genera of Rosaceae. The data also support the hypothesized hybrid origin of subfamily Maloideae because sampled individuals have two highly divergent types of waxy sequences similar to their presumptive parents.