Genetic variation for morphological and allozyme variation in relation to population size in Clarkia dudleyana, an endemic annual

The maintenance of genetic variation within populations is expected to allow species to respond to evolutionary challenges such as selection and environmental stress. Larger populations are generally expected to maintain larger amounts of genetic variation. Although several studies have found a positive relationship between population size and levels of genetic variation for molecular markers such as allozymes, few comparisons have been made between molecular measures of variation and genetic variation that is likely to be ecologically important. Most ecologically important traits require quantitative genetic analyses. I examined the relationship between levels of genetic variation and population size for both allozymes and morphological traits in a California endemic annual plant, Clarkia dudleyana. Levels of genetic variation for allozymes did not show a significant positive relationship with population size. The level of genetic variance for all of the 18 morphological traits exhibited no significant relationship with population size. Further, allozyme heterozygosities were not related to levels of quantitative genetic variation. These results indicate that levels of allozyme variability do not predict levels of genetic variation for morphological traits in C. dudleyana, suggesting that molecular measures of variation, in general, differ from quantitative genetic measures. These results imply that conservation genetic studies should generally focus on aspects other than measuring levels of genetic variation found within populations.