Evolutionary Factors Contributing to Genetic Differentiation between Subpopulations of Raphanus Raphanistrum

Abstract

The plant species Raphanus raphanistrwn, wild radish, has been found growing in nearly every continent in the world, with the different populations having a large amount of phenotypic variation from each other. A previous study proved that the majority of these phenotypic differences were due to genetic differentiation between populations. This was done by obtaining seeds from nine different populations throughout the world, growing them in a common garden greenhouse where all environmental differences have been removed, and measuring various traits. The goal of my study was to analyze these same populations and determine if the genetic differentiation was due to random genetic drift or differential natural selection, as well as to determine if noted genetic similarities were caused by convergent natural selection. To do this, I analyzed neutral sites in the genome of R raplwnistrom and used FSTanalysis to determine the total genetic differentiation. I also measured 13 phenotypic characteristics, including both floral and growth traits. Qsr analysis was then done on these traits to determine the additive genetic variation. By comparing the QST and PST values it was possible (0 determine the relative contribution of drill and selection to the overall generic differentiation or genetic similarity of the various populations of R. raphanislrum.