Madson, Hannah , Caruso, Christina , Case, Andrea .
Effects of non-selective mechanisms on structured population sex-ratio variation in gynodioecious Lobelia siphilitica (Lobeliaceae).
Gynodioecy - the coexistence of females and hermaphrodites in a population - is a common genetic polymorphism in plants. Such polymorphic systems are useful for examining variation across a species' geographic range when the two sexes are unevenly distributed. Variation in sex ratio may reflect both selective mechanisms, if the relative fitness of the sexes varies among populations, and non-selective mechanisms, if drift, founder effects, and gene flow affect the distribution of sex-determining alleles. Here, we used chloroplast sequence variation to evaluate hypotheses about how non-selective mechanisms affect population sex-ratio variation in Lobelia siphilitica. Females are more common in the southern-central portion of the range, where mean annual temperatures are higher, but populations are also smaller (N < 100). Central populations may experience higher gene flow than peripheral populations, while smaller populations may exhibit stronger effects of genetic drift. We found substantial among-population variation (Fst = 0.67) that was not explained by either population size or sex ratio. Although evidence for isolation by distance was weak, four out of five rare chloroplast haplotypes were geographically restricted, and distance from central populations explained a significant portion of the among-population variation. Thus, population dynamics may differ in the peripheral compared to the central portion of the species range. If metapopulation dynamics differ at the range edge, this may explain why females are rare in peripheral populations of L. siphilitica.
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1 - Kent State University, Department of Biological Sciences, Box 5190, 256 Cunningham Hall, Kent, OH, 44242-0001, USA
2 - University Of Guelph, Department Of Integrative Biology, New Science Complex, 50 Stone Road East, GUELPH, ON, N1G 2W1, Canada
Presentation Type: Poster:Posters for Topics
Location: Khorassan Ballroom/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 5:30 PM