Breeding systems and genetic variation in Amsinckia spectabilis (Boraginaceae)

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Abstract
Samples from 10 populations of Amsinckia spectabilis var. spectabilis and three populations of A. spectabilis var. microcarpa were analyzed for allelic variation at 17 allozyme loci using stareh gel electrophoresis. This species is a self-compatible annual which has heterostylous populations, homostylous populations, and mixed populations containing heterostylous and homostylous plants. Heterostylous populations had the highest outcrossing rates, homostylous populations the lowest, and mixed populations were intermediate in outcrossing rate. Outcrossing rate is highly correlated with the average stigma–anther separation in flowers in the populations. Genetic variability was highest in heterostylous populations, lowest in homostylous populations, and was intermediate in mixed populations, although one large homostylous population was as variable as were mixed populations. Genetic identities among populations were very high with the exception of the two northernmost, isolated homostylous populations which were fixed for rare alleles at some loci. In the rest of the populations, genetic identities were higher between populations of the same taxonomic variety than they were in intervarietal comparisons.