Whole genome duplication in a threatened grassland plant and the efficacy of seed transfer zones

Abstract

AbstractAimSeed transfer zones are geographically defined areas in which the interpopulation mixing of plant propagules is presumed to be genetically beneficial and unlikely to result in outbreeding depression. Crossing between individuals that differ in ploidy (the number of whole genome duplications) commonly produces sterile or mostly sterile progeny, but the landscape distribution and occurrence of polyploids is poorly known for rare plants. Seed transfer zones could provide adequate protection for rare plants with unrecognized ploidy variation provided that the distribution of ploidal variants coincides with seed zone delineations. We studied the range‐wide distribution of polyploids in a threatened legume to determine whether U.S. Fish and Wildlife Service endorsed seed transfer zones have adequate protection from inadvertent mixing of individuals with non‐matching ploidy.LocationPacific Northwest, USA.MethodsWe used genotyping with nuclear DNA simple sequence repeats and flow cytometry to screen for the presence of polyploids over the known range of Lupinus oreganus (Fabaceae).ResultsGenotyping (895 plants) and flow cytometry (198 plants) from 34 populations revealed that mixed‐ploidy and polyploid populations were not limited to the margins of the species range. Both mixed‐ploidy and polyploid populations occurred within every seed transfer zone and the nearest population (within each zone) appeared to be composed entirely of diploid individuals.Main conclusionsLupinus oreganus seed recovery zones, assumed to be ‘genetically safe’ areas to transfer seed among populations, would not prevent the mixing of incompatible ploidal lineages. For L. oreganus, and other rare plant species with undocumented differences in whole genome duplication, interpopulation mixing without precautionary genetic screening could compromise the success of conservation projects involving interpopulation seed transfer. We recommend screening rare plant populations for variation in whole genome duplication prior to the implementation of interpopulation seed mixing projects.