Evolutionary Factors Contributing to Genetic Differentiation between Subpopulations of Raphanus Raphanistrum
Howe, Stephen R.
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The plant species Raphanus raphanistrwn has been demonstrated to have phenotypic differences between populations located through out the world. A previous study proved that the majority of these phenotypic differences were due to genetic differentiation between populations. In this study, I used FST and QST techniques to analyze these same traits in order to determine if the genetic differences were caused by random genetic drift or by differential natural selection, as well as to determine if the genetic similarities were caused by convergent natural selection. To do this, I grew plants from seven populations around the world in a greenhouse. I measured and analyzed thirteen traits during the experiment to determine if significant differences were present, and then combined the data with parental data to produce QST values for each trait. I also analyzed suspected neutral sites in the genome to produce FST values. The average FST value was found to be 0.115. No QST value fell within two standard errors of this value, implying that none of the differences was caused solely by genetic drift. The height of the first flower, corolla tube length, number of ovules produced, stamen dimorphism, time to germination, time from germination to flowering, anther exertion, long anther length and short anther length were all found to have QST values significantly higher than the mean FST value, implying they underwent divergent selection. Short filament length, long filament length and pistil length all had smaller QST values than the mean FST value, implying they underwent convergent selection.