| Popis: |
In this thesis, I studied the genetic structure and mating system of the invasive shrub Lonicera maackii (Rupr.) Maxim. (Caprifoliaceae). This shrub is native to eastern Asia, and was introduced to the U.S. in 1898 for horticultural purposes. Lonicera maackii is currently considered an aggressive invasive plant, and when present, is often the dominant understory shrub in forested areas of southwest Ohio.First, I tested the hypothesis that L. maackii is spreading into previously uncolonized areas by way of multiple long-distance dispersal events followed by local expansions. I examined the genetic structure of 42 populations of L. maackii from Hamilton, Franklin, Butler, Preble, Darke and Miami counties in Ohio, and Wayne County in Indiana. Darke County is the most recent area in Ohio experiencing a rapid colonization. My findings revealed high allelic diversity (Na = 8.13), high heterozygosity (Ho = 0.71) and low levels of inbreeding (FIS = 0.06) across all populations. Low population differentiation (FST = 0.08) was found between populations, with only 10% of the molecular variation attributed to differences among populations. A significant correlation between geographic and genetic distance was found among all possible pairwise populations (Mantel correlation = 0.23, p = 0.01) suggesting that established populations may expand their range as advancing fronts. Further analysis using the program Structure revealed significant levels of admixture within individuals and within woodlots, suggesting that, in addition to local expansion of established woodlots, animal-mediated long-distance seed dispersal aids in the spread of L. maackii and plays a key role in maintaining genetic diversity.For my second study, I examined the mating system of L. maackii in one woodlot, comparing edge and interior plants. My findings support the notion that L. maackii is a predominantly outcrossing plant (tm = 0.97), with no significant differences between the outcrossing rates among edge and interior plants. However, there were differences in the correlation of paternity among progeny of edge and interior plants, suggesting differences in the average number of pollen donors siring their seed crop; effective number of pollen donors (Nep) was lower for edge plants. I found significant heterogeneity in allele frequencies among pollen and ovule for both edge and interior plants. I argue that differences in pollen frequencies and number of sires is most likely due to the disparities in visitor community, the time and intensity of flower anthesis among pollen donors, and non-random mating of genotypes during outcrossing events. |
