QUANTITATIVE TRAIT LOCI DIFFERENTIATING THE OUTBREEDING MIMULUS-GUTTATUS FROM THE INBREEDING M-PLATYCALYX

Theoretical predictions about the evolution of selfing depend on the g enetic architecture of loci controlling selfing (monogenic vs. polygen ic determination, large vs. small effect of alleles, dominance vs. rec essiveness), and studies of such architecture are lacking. Mie inferre d the genetic basis of mating system differences between the outbreedi ng Mimulus guttatus and the inbreeding M. platycalyx by quantitative t rait locus (QTL) mapping using random amplified polymorphic DNA and is ozyme markers. One to three QTL were detected for each of five mating system characters, and each QTL explained 7.6-28.6% of the phenotypic variance. Taken together, QTL accounted for up to 38% of the variation in mating system characters, and a large proportion of variation was unaccounted for. Inferred QTL often affected more than one trait, cont ributing to the genetic correlation between those traits. These result s are consistent with the hypothesis that quantitative variation in pl ant mating system characters is primarily controlled by loci with smal l effect.