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Title: The role polymorphism and life history trade-offs during range expansion
Author: Keenan, V. A.
ISNI:       0000 0004 7970 4210
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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Understanding how fast a species invades new habitat or expands its range is of critical importance. As a result of climate change, the number of species expanding their native range is increasing. More exotic species are being inadvertently released into habitats unprepared for their arrival. Evidence suggests that expansions and invasions are occurring at faster rates due to the evolution of dispersal. However, few mathematical models exist that consider how the rate of spread is influenced by dispersal life history. This thesis addresses the gap in understanding using mathematical models to make predictions about invasive spread under a dispersal-reproduction tradeoff. Using deterministic models and simulations, we build upon existing theories of anomalous invasion speeds, extending the cases for which they are known to exist. We have also examined the literature and performed a meta-analysis to determine the prevalence of dispersal trade-offs in nature that can be used to validate existing theory. We show that anomalous invasion speeds are a robust phenomenon that are possible within populations that express a general degree of polymorphism, but at most 2 phenotypes determine the speed of invasion. This result was found to persist when interactions among species were non-neutral, moreover, those interactions do not influence the invasion speed. Invasion speeds are shown to decrease in the presence of another species, even when one of the 2 phenotypes that determined the invasion speed is out-competed to the point of negative net growth. Anomalous invasion speeds are also shown to exist when a species reproduces sexually. When that species is diploid, we find the invasion speed is sensitive to how the heterozygote expresses its dispersal and reproductive traits. Overall, we found that accounting for the life histories related to dispersal has surprising and robust effects that alter the dynamics of biological invasions.
Supervisor: Cornell, Stephen ; Saccheri, Ilik Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral