FITNESS-RELATED TRAITS OF ALLOZYME GENOTYPES IN BROMUS-HORDEACEUS L. (POACEAE) ASSOCIATED WITH FIELD HABITAT AND EXPERIMENTAL FLOODING

Genetic variation at alcohol dehydrogenase and phosphoglucose isomeras e loci in Bromus hordeaceus has in an earlier study been found to show substantial microgeographic spatial structuring. The present study re ports differences in fitness related characters between the enzyme gen otypes, both from a field study and a greenhouse experiment. The field study showed overall differences in seed set between allozyme genotyp es and also that Pgi-1b genotypes differed in number of seeds set at d ifferent levels of herb cover in their habitat. In the greenhouse, dry , normal or flooded conditions were applied. Seeds from individuals wi th the Adh-1b-11 genotype matured faster in the dry and slower in the flooded treatments than did seeds from individuals with the Adh-1b-22 genotype. Individuals containing Pgi-1b-1f1f alleles and Adh-1b-11 all eles are more plastic than individuals with other allele combinations, meaning that allozyme variation could partly explain what could be se en as adaptive phenotypic plasticity. Mean seed weight was different b etween dry and flooding treatments for Pgi-1b genotypes. There were al so direct effects of allozyme genotype on the probability of survival, total plant weight, weight of reproductive parts, seed weight, days t o seed maturation and the percentage of reproductive parts out of the total plant weight. (C) 1998 The Linnean Society of London.