Clarification of basal relationships in Rubus (Rosaceae) and the origin of Rubus chamaemorus

• Main Author: Michael, Karen
• Format: Others
• Published: TopSCHOLAR® 2006
• Subjects: Biology; Fruit Science
• Online Access: http://digitalcommons.wku.edu/theses/250; http://digitalcommons.wku.edu/cgi/viewcontent.cgi?article=1253&context=theses

Determination of phylogenetic relationships among ancestral species of Rubus has been elusive. Most Rubus species (including blackberries and raspberries), representing nine of the 12 subgenera, occur in a large, well supported clade named 'A' for reference). The remaining nine species are excluded from this group and represent three subgenera: subg. Anoplobatus (R. bartonianus, R. deliciosus, R. neomexicanus, R. odoratus, R. parviflorus, R. trilobus), subg. Chamaemorus (R. chamaemorus), and subg. Dalibarda (R. lasiococcus, R.pedatus). In addition, Rubus dalibarda L. is often treated in its own monotypic genus as Dalibarda repens L. Phylogenetic analyses of DNA sequence data from chloroplast regions and the nuclear ribosomal DNA internal transcribed spacer ITS 1 - 5.8S - ITS 2; ITS) region have not resolved basal relationships in Rubus and the position of Dalibarda repens has varied from being the sister group to Rubus to nested within it. However, monophyly of American subg. Anoplobatus species is supported by both genomic regions. Our goal was to clarify ancestral relationships, investigate the position of Dalibarda repens relative to Rubus, and examine the origin of the circumboreal, octoploid species R. chamaemorus using sequence data from one additional chloroplast DNA region, trnS-trnG, and the singlecopy nuclear gene Granule-Bound Starch Synthase (GBSSI-1). Parsimony analyses of trnS-trnG sequences indicate a basal trichotomy, while R.chamaemorus is strongly supported as sister to R. pedatus. A combined cpDNA (trnS-trnG and three other regions) parsimony analysis indicates that subg. Anoplobatus is sister to clade A, and strongly supports Dalibarda repens as sister to R. lasiococcus. This suggests that Dalibarda repens be classified as R. dalibarda consistent with Linnaeus (1762) and Focke (1910). Parsimony analyses of GBSSI-1 sequences result in a large polytomy and do not recover clade A. The presence of three (GBSSI-la, GBSSI-1 (3 and GBSSI-ly) putative forms of the gene is observed. However, separate parsimony analysis of GBSSIly sequences demonstrates strong support for clade A and the monophyly of ubg. Anoplobatus. In this analysis, two different alleles are present in R. chamaemorus; one occurs outside clade A (sister to R. lasiococcus) and the other nests within clade A (sister to R. arcticus). Thus these data suggest that R. chamaemorus may be an ancient allopolyploid. The phylogenetic position of Dalibarda repens relative to Rubus cannot be resolved by existing GBSSI-1 data.