CLIMATIC NICHE MODELING REVEALS DIVERGENCE BETWEEN CYTOTYPES IN EUTREMA EDWARDSII (BRASSICACEAE)

Polyploidy among plants is most frequent in the arctic where glaciation cycles put selective pressures on populations by repeated fragmentation and fluctuation in climate. Polyploids should have been more fit in novel habitats as glaciers receded due to increased genetic material and novel gene products, which results in phenotypic plasticity and rapid adaptation. Higher ploidy is then expected to confer a broader tolerance of environmental conditions. Eutrema edwardsii R. Br. (Brassicaceae) is an arctic-alpine mustard with a near circumpolar distribution that occurs as a tetraploid, hexaploid and octaploid. We used flow cytometry to document the distribution of polyploid cytotypes using herbarium tissue and modeled the niche of each cytotype to test for niche differentiation. Flow cytometry revealed four cytotypes among 85 individuals. Notably, 60% of herbarium tissue assays were successful using tissue up to 50 years old. Principle components analysis was performed on 20 climatic variables, of which, the first four axes were used as environmental variables for niche modeling. Niche models were created for tetraploid and hexaploid populations and used to calculate niche overlap (Shoenerâ s D). Overlap between tetraploid and hexaploid models (D = 0.534) is lower than the null distribution (D = 0.681 - 0.944) supporting the hypothesis of niche divergence.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author