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Evolution and consequences of the rate of self-fertilizationThe evolution of self-fertilization ('selfing') from outcrossing occurs very commonly in plants. Selfing rates vary greatly among species of plants and among animals, and strongly affect a population's genetic qualities, demography, and evolutionary potential. What drives mating system evolution? What are the consequences of shifts in selfing rate? While much progress has been made on these questions in the last three decades, much work remains to be done.
Pleiotropy and selfing rate evolutionMost models of mating system evolution consider selection that occurs only during mating. However, a growing body of evidence suggests that floral qualities can also affect survival, so that genes that affect floral traits may affect both survival and selfing rates. How do such genes affect the evolution of selfing rate? Using a series of mathematical models, I showed that pleiotropy between survival and selfing rate allows the evolution of intermediate selfing rates despite high inbreeding depression, which helps explain previously enigmatic selfing rates in some species.
Maternal environmental effects and inbreeding depressionInbreeding depression, the reduced fitness of inbred offspring, represents a strong barrier to the evolution of selfing, and is a common conservation concern. Theory predicts that fluctuations in inbreeding depression may select for intermediate selfing rates, and many studies show that inbreeding depression differs between environments. However these empirical studies also typically confound a 'stressful' environment with a 'novel' environment, which clouds interpretation. To address this concern, Kay Hodgins, Dilara Ally and I used Mimulus guttatus to test whether inbreeding depression expressed by offspring in a given environment depends on the environment experienced by their mother. Such effects were apparent for asexual reproduction, but not for sexual reproduction.
The consequences of selfing rate for introgressionSelfing rates commonly differ among plant populations or between closely related species. Selfing rate differences can affect the extent and direction of introgression between plant species, but are rarely examined. For my post-doc with Richard Ennos, I used ddRAD sequencing to examine introgression between the outcrossing and selfing species, Geum rivale and G. urbanum, respectively (photos right; G. urbanum has yellow flowers; G. rivale has cream coloured, downward facing flowers). Surprisingly, we found little evidence for introgression, but did find evidence for strong extrinsic selection against post-F1 hybrids.
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Female (top) and male flowers of Silene latifolia. Images from Lynda Delph's website.
Photo from www.discoverlife.org
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