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Testing Janzen’S Physiological Barrier Hypothesis Through Experimental Evolution And Biogeographic Studies On Sister Species Pairs, Vincent John Fasanello

Arts & Sciences Electronic Theses and Dissertations

Background: Janzen’s physiological barrier hypothesis suggests that variation in the effectiveness of physiological barriers to dispersal underlies global patterns of speciation and biodiversity. He noted that because a species’ physiology often evolves to match the range of conditions it has experienced in evolutionary history, it is likely that lineages that occupy habitats with wider ranges of temperature variation will tend to be better at dispersing across thermal gradients and will therefore be less likely to speciate as a result of mountain barriers. Despite decades of research into different aspects of this fundamental hypothesis, its assumptions and predictions remain largely untested. …