Pollen morphology of Ligusticum (Apiaceae) in Canada
The pollen morphology of the four Canadian taxa of Ligusticum (L. calderi, L. canbyi, L. scothicum ssp. scothicum, and L. scothicum ssp. hultenii) was studied under the light microscope and compared with that of other Apiaceae common on the Pacific coast of British Columbia and adjacent Alaska. Ligusticum calderi and L. canbyi compose one pollen type with a subrhomboidal outline in equatorial view and a triangular outline in polar view with pores located at the apices of the amb. Endopores are X-, H-, or dumbbell-shaped. The L. scothicum type is rectangular in equatorial view and circular in polar view, with pores arranged on the circumference. Endopores are usually rectangular to oval. Ligusticum calderi pollen is larger and thus distinct from L. canbyi pollen. All other Apiaceae pollen types examined are distinct from the L. calderi type because their pores are positioned between the lobes of the amb and because of differences in other characters. Since L. calderi pollen is readily separated from other Apiaceae on the British Columbia coast, it can be used to study the history of this geographically restricted species and the possibly refugial species associated with it. The size differences between L. calderi and L. canbyi pollen suggest that they are distinct species.