9306473 Kohn Natural populations of the emergent-aquatic annual Eichhornia paniculata often contain two readily identifiable genetic morphs whose rates of self fertilization average 0.8 and 0.2, respectively. We will take advantage of these populations to evaluate several recent theoretical predications of critical importance for understanding the evolutionary dynamics of inbreeding depression and mating system change. We will measure morph-specific levels of self fertilization and male outcrossing success to obtain complete information on morph-specific gamete transmission in these natural populations. This will provide some of the first information on how a floral morphology that increases the selfing rate affects other aspects of gamete transmission. We will evaluate morph-specific inbreeding depression to see if genes that control the mating system are in disequilibrium with fitness alleles responsible for inbreeding depression. Such associations are expected under many recent theoretical models and can alter expectations based on population mean levels of inbreeding depression. However, associations between mating and fitness alleles have not as yet been demonstrated in any natural population of hermaphroditic plants. We will resample morph frequencies in populations first examined over 10 years ago to gain information on the stability of morph ratios over time. Previous measures of transmission in these populations provided an expectation of rapid decline in the frequency of the morph with the lower selfing rate. If morph frequencies have not changed, our measures of transmission and viability should shed light on factors maintaining mating system polymorphism. If the morph with the lower selfing rate is in decline, we will gain an unusually well-documented example of evolution by natural selection over a human time scale. The results will provide useful insights into factors promoting stability or instability of mixed mating systems and t he dynamics of inbreeding depression in natural populations.***
