Variation in the mating system of bidens menziesii (Asteraceae) in relation to population substructure

Abstract

The mating system of the Hawaiian plant Bidens menziesii subsp. filiformis was examined in four populations, using progeny arrays assayed at four polymorphic aiiozyme loci. Average selling rates ranged near 50 per cent in ail populations. Evidence that consanguineous (non-self) matings contributed to selling was given by (1) gene frequency variation among subsites in two populations and (2) significant among-piant regressions of outcrossing-pollen gene frequency upon ovule genotype, based upon mating system estimates for individual plants. These estimates for individual plants, whose properties are discussed, showed significant among-piant variation for (1) single-locus selling rates in three populations, (2) multilocus selling rates in two populations, and (3) pollen gene frequency in three populations. Expected effects of population substructure upon among-piant variation of selling and pollen gene frequency are given in terms of Wright’s F statistics and parameters of the “effective selling model”. In three populations, much of the single-locus selling variation was manifested in a tendency for inbred plants to effectively self more than outbred plants. This assortment of selling, termed “inbreeding assortative selling”, maintains the spatial variation of Wright’s F and is a covariation of gene fixation in parents with genetic similarities between mates. This variation of inbreeding might allow the localised generation and establishment of homozygous genotypes of evolutionary significance. © 1985 The Genetical Society of Great Britain.