Rhododendron columbianum has been determined to be a diploid using flow cytometry by
Dr. João Loureiro, Dr. Silvia Castro, and Mariana Castro
Plant Ecology and Evolution Group,
Centre for Functional Ecology,
Department of Life Sciences,
Faculty of Science and Technology,
University of Coimbra, Portugal
Rhododendron columbianum is often documented as being a hybrid between Rhododendron groenlandicum and Rhododendron neoglandulosum. Since Rhododendron groenlandicum and Rhododendron neoglandulosum are tetraploid, Rhododendron columbianum, being diploid, is most likely a separate species.
Summary of Ploidy Levels
Diploid Rhododendron columbianum,
Diploid Rhododendron subarticum,
Diploid Rhododendron subulatum China,
Tetraploid Rhododendron diversipilosum,
Tetraploid Rhododendron diversipilosum 'Milky Way',
Tetraploid Rhododendron groenlandicum,
Tetraploid Rhododendron groenlandicum Saco Bog, Maine,
Tetraploid Rhododendron hypoleucum,
Tetraploid Rhododendron neoglandulosum,
Tetraploid Rhododendron tolmachevii,
Tetraploid Rhododendron tomentosum Turku Archipelago
Source: Kristian Theqvist
Source: Hans Eiberg
Source: Robert MacIntyre
John and Sally Perkins
