Reproductive Biology and Ecological Genetics of Three Prairie Forbs
Kim, Eun Sun
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My work aimed at investigating the aspects of reproductive biology and population genetics of three iconic prairie forbs. Microsatellite genotypes were used to determine the extent of clonal growth, genetic diversity, and genetic structure in nine populations of Asclepias lanuginosa and five populations of A. viridiflora. A nearly complete shift in the mode of reproduction, from sexual to asexual, in A. lanuginosa, appears to be the most immediate threat to survival of A. lanuginosa in these fragmented prairie remnants. For my work on Castilleja coccinea, the focus was understanding the biology underlying bract color polymorphism. Castilleja coccinea displays showy scarlet bracts throughout its range in eastern North America, but yellow bracts are predominant colors of some Midwestern populations. These populations exhibit a bract color polymorphism, with each population having predominantly yellow or scarlet bracts. I conducted hand-pollination experiments in two nearby populations, one predominantly yellow and one predominantly scarlet. Both color morphs of C. coccinea were self-compatible. I found reproductive trade-offs between a higher reproductive output in the scarlet morph and a reproductive assurance advantage in the yellow morph, which may explain the maintenance of the polymorphism in C. coccinea. Population genomics of the Midwestern C. coccinea was conducted using 958 single nucleotide polymorphisms that were variable among 10 populations and 5,532 SNPs that were variable between the color morphs, which were discovered by double digest Restriction-Site Associated DNA sequencing. Results suggest the distribution of bract colors is not correlated to the patterns of population structure and genetic diversity. Further, the two color morphs were not genetically differentiated. Geographic distance or evolutionary history scenarios failed to explain the apparent population structure and genetic differentiation. I found some indirect evidence that neutral processes may be responsible. Inheritance patterns of bract colors in C. coccinea were determined using a hand-pollination experiment among yellow, orange, and scarlet bract colored individuals. Bract color of C. coccinea is likely primarily controlled by multiple alleles at a single locus and follows an autosomal dominant mode of inheritance with yellow dominant over scarlet and orange.
bract color polymorphism