Understanding the Causes of Geographic Variation in Sex Ratio of a Gynodioecious Plant

Kent State University, Kent OH

Investigators

Abstract

Evolutionary biologists have long been interested in understanding how populations of organisms become different from one another, because it is a necessary precursor to speciation. Variation in population sex ratio (for example, the number of females vs. males, or females vs. hermaphrodites) provides an excellent model for investigating mechanisms of population differentiation. Because the population sex ratio determines the identity and number of available mates, it affects how genetic variation is distributed within and between populations. This project will investigate why the proportion of females vs. hermaphrodites in a flowering plant (Lobelia siphilitica) are higher in small populations and at warmer sites. We will test whether female frequencies vary because of natural selection, or if other evolutionary forces, such as genetic drift and gene flow, are preventing many populations from reaching an equilibrium sex ratio. Distinguishing the effects of these different evolutionary mechanisms is important because they produce distinct patterns of population genetic structure. This research will provide a framework for evaluating how breeding systems influence the ability of species to modify their range in response to climate change, particularly global warming. If female L. siphilitica plants are more common in areas with higher annual mean temperatures because of natural selection, then populations should become more female-biased in response to global warming, which could affect migration rates and species persistence.