COVARIATION OF SELFING RATES WITH PARENTAL GENE FIXATION INDICES WITHIN POPULATIONS OF MIMULUS GUTTATUS

Wright's gene fixation index F and two single-locus effective selfing rates-the selfing rate at loci with fixed alleles, and the selfing rate at loci without fixed alleles-were estimated in five populations of Mimulus guttatus. These two effective selfing rates describe the inbreeding observed at a single locus when both uniparental and biparental inbreeding are practiced. Estimates were made using progeny arrays assayed for six allozyme loci and two morphological loci exhibiting dominance. The average of the two selfing rates computed for subpopulations (ca. 10 m diameter) ranged from 24% to 59%, with a mean of 37%. When computed for populations (ca. 1 km diameter), average selfing rates were about 10% higher. In four populations, the selfing rate at loci with fixed alleles was higher than the selfing rate at loci without fixed alleles. Thus, the covariance of selfing with parental gene fixation was positive. In one of the populations, estimates for individual plants sampled along a transect gave positive correlations for selfing rates and for gene-fixation indices between adjacent plants. A highly positive correlation between selfing rate and gene fixation of individual plants was also observed. In another population, the covariance of selfing with gene fixation was higher for a locus causing leaf spots than for allozyme loci. This covariance is partially caused by 1) variation in homozygosity among neighborhoods and 2) biparental inbreeding within neighborhoods. The consequences of this covariance are discussed.