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Using Callosobruchus maculatus as a model system for studying ecological responses to genetic diversity and evolutionary responses to selection
AuthorBurls, Kevin J.
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Genetic variation for fitness-related and ecological traits is crucial for the ecological and evolutionary responses of populations. Studying the processes by which genetic variation influences ecological and evolutionary processes has greatly benefitted from experimental studies. The seed beetle Callosobruchus maculatus has become a model system for studying quantitative trait variation and evolution in experiments that either manipulate genetic variation or artificially select on one more traits. In my dissertation I use C. maculatus as a model system for studying the ecological and evolutionary responses of a population via two different experimental approaches. Chapter II details an experiment to measure the ecological consequences of genetic diversity. We used replicate populations that varied in their genotypic diversity, and also their individual host preference, and measured how different combinations of genotypes and genotypic diversity influenced group resource use and productivity. We found a nonlinear increase in the benefits of diversity; that is, intermediately diverse groups had the highest productivity. In Chapter III we used an artificial selection experiment to measure if traits involved in the evolution of dispersal are related to important life history traits in this system, and if these correlations between traits interact to influence the ability of the population dispersal distributions to shift over time. We selected on replicate C. maculatus populations for 20 generations. While we found an initial increase in offspring dispersal, this was not followed by continuous evolution in dispersal distance over time. However, following selection we found clear differences between dispersal and life history traits that suggest energetic constraints involved in life history traits may constrain the ability of dispersal distributions to increase. In Chapter IV we used beetles from the selection experiment to measure the presence and strength of correlations between different traits that are involved in organismal movement. We found that high dispersal individuals moved faster, rested less, and moved further overall than their control counterparts. These results suggest that these traits may be developmentally linked, which may make it easier for a complex trait (organismal movement over a lifetime) to evolve multiple components simultaneously.