Abstract
The influence of population density on pollinator movements and outcrossing rates was studied in experimental arrays of Mimulus ringens (square-stemmed monkeyflower), a wetland perennial species with a mixed-mating system. Each population was composed of genets with unique multi-locus combinations of homozygous genotypes, facilitating determination of outcrossing rates through paternity exclusion. Replicate arrays were cloned from the same set of genets to minimize differences in floral and vegetative morphology among density treatments. Two arrays were planted at each of three spacings typical of the range of densities found in natural M. ringens populations. Both the proportion of pollinator flights between plants and the frequency of outcrossing were significantly greater at high density. These results suggest that ecological and demographic factors, such as population density, can significantly influence levels of inbreeding in species with mixed-mating systems.
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Acknowledgements
We are grateful to James Reinartz and Lou Nelson for designing and building experimental research gardens at the UW-Milwaukee Field Station. We thank Thomas Schuck for advice and assistance propagating M. ringens. Norman Ellstrand, Diane Marshall, James Reinartz, William Schuster, Donald Waller, Joyce Witebsky and two anonymous reviewers provided helpful comments on the manuscript. This research was supported by United States National Science Foundation grant DEB-9119311 to JDK and by a research award from the Graduate School of UW-Milwaukee. This is publication number 147 of the UW-Milwaukee Field Station.
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Karron, J., Thumser, N., Tucker, R. et al. The influence of population density on outcrossing rates in Mimulus ringens. Heredity 75, 175–180 (1995). https://doi.org/10.1038/hdy.1995.121
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