The endemic Hawaiian raspberries Rubus hawaiensis and R. macraei (both subgenus Idaeobatus) had been thought to be closely related species until recent molecular studies demonstrated otherwise. These studies suggest that they are the products of separate colonizations to the Hawaiian Islands. Affinities of R. hawaiensis to R. spectabilis of western North America were clearly confirmed. However, no clear relation to R. macraei has been published. This study was initiated to examine species of subg. Idaeobatus from the surrounding Pacific region as well as species from other subgenera to better evaluate biogeographic and phylogenetic affinities of R. macraei by means of chromosome analysis and molecular data using the chloroplast gene ndbF. Results show that R. macraei clusters in a clade with species of blackberries, subg. Rubus, and of these it is most closely linked to R. ursinus. Chromosomally, R. macraei is 2n = 6x = 42, a number that would be a new report for subg. Idaeobatus. However, polyploidy is common in subg. Rubus. Analyses indicate that R. macraei and R. hawaiensis are derived from separate colonizations from North America and that similarities between them are due to convergent evolution in the Hawaiian environment.
Additional publication details
Phylogeny and biogeography of pacific Rubus subgenus Idaeobatus (Rosaceae) species: Investigating the origin of the endemic Hawaiian raspberry R. macraei