This week EEB features Queen’s University Department of Biology postdoc Dr. Maggie Bartkowska who will present:
Identifying causes of natural selection and assessing how asexual reproduction influences selection on genome-wide diversity.
Selection is assumed to be a central process in nature. Although much effort has been made to quantify selection in nature, whether and how selection drives phenotypic and molecular evolution remains unknown for most systems. This is because the agents of selection and variation in selection (through time and space) are rarely assessed, and populations that deviate from random mating may experience selection differently than predicted by theoretical models. I address these gaps in two study systems. First, using a combination of field observations and experimental manipulations in Lobelia cardinalis (cardinal flower), I identify agents of selection on floral characters, and show that successful pollen transfer can vary with local floral density. In a species with separate male and female flower phases, such as L. cardinalis, successful pollen transfer varies with the density and ratio of surrounding male and female flowers, implying that the local floral environment may shape selection on floral traits. Second, using Next Generation Sequencing data, I infer the history of selection and reproduction in Spirodela polyrhiza (giant duckweed), a flowering plant thought to be almost exclusively asexual. Unlike other angiosperms, purifying selection appears to be reduced in S. polyrhiza and linkage disequilibrium across the genome is high, consistent with the expectation that selection will be less effective in populations with reduced levels of recombination. Understanding adaptive evolution, and how deviations from an idealized population influence adaptive evolution, is critical to explaining patterns of phenotypic and molecular diversity across all taxa.
The EEB Seminars run weekly, on Thursdays, in the EEB Lounge of the BioSciences Complex, Room 4338, from 12:30-1:30pm. Light refreshments are served starting at 12:15.