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Rubin, Ilan Naftali

University of British Columbia

Understanding the mechanisms that generate and maintain diversity in ecological communities is perhaps the central question of ecological theory. Early theoretical contributions by Robert MacArthur formalized multi-species coexistence by considering how frequency dependent competition can naturally partition a continuous trait space into distinct niches. More recently, the adaptive dynamics framework has extended these ecological dynamics based on frequency dependent interactions to evolutionary timescales, creating a model capable of describing adaptive speciation and the emergence of diversity through natural selection. In this thesis I expand on these theories to help provide a greater understanding of the mechanisms that drive species coexistence and the maintenance of variation in ecological communities. In Chapter 2, I compare the diversity on ecological versus evolutionary timescales by comparing the diversity of randomly assembled communities to that of the ESS (evolutionary stable state, and the theoretical endpoint of evolution). I show that when randomly assembled, ecological communities can be saturated (having a diversity greater than the evolutionary stable state), yet saturation becomes prohibitively hard in higher dimensions. In Chapter 3, I show how Red Queen evolutionary dynamics can trap communities in low diversity metastable states. In Chapter 4, I combine perhaps the two most iconic theories of evolutionary diversity, the rugged fitness landscape and negative frequency-dependence, into one model. In doing so I show how on very rugged landscapes evolutionary dynamics mimic the local optimization and stochastic peak-shift dynamics predicted by rugged fitness landscape theory. However, the diversity each system can support is determined by the relative strength of frequency dependence and the shape of the global landscape, not the ruggedness. In Chapter 5, I consider the evolution of phenotypic heterogeneity, i.e., when genetically identical individuals have different phenotypes. I show that there is a race between diversification leading to a population of specialists and the evolution of heterogeneity, which leads to a division of labor.

Text

2022-08-23

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/82452

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/