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Boyd, Mark Allen
(1986).
DOI: https://doi.org/10.21954/ou.ro.000114f8
Abstract
Genetic theory has predicted the spread of homostyly through heterostyle populations but this has not happened over the last 40 years. This thesis compares the ecology of the three primrose morphs (pin, thrum, homostyle) to determine whether ecological differences between the morphs may limit the spread of homostyles.
Mean individual seed weight decreased with the number of seeds per capsule. Heterostyle seed production was pollinator limited and consequently heterostyles tended to produce larger seeds than homostyles. Seed size appeared to be more important than the phenotype (morph) of the mother in determining germination success. Larger seeds germinated better and may survive better in the soil.
Survival of seedlings in experimental populations and of adults in wild populations was higher for homostyles than for heterostyles with thrums faring worst.
Adult survival was dependent on the number of flowers produced in the preceding flowering season. Survival data are presented as life tables.
A matrix model of population growth is presented showing that homostyles would be expected to increase relative to heterostyles on purely ecological grounds. However, a sensitivity analysis shows that the spread of homostyles may be limited by seed survival in the soil.