Evolutionary Genetics and the Ecology of Speciation

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Why are there so many animal species? Why are so many species ecologically specialized, using a narrow range of resources and habitats? Biologists have long suspected that ecological specialization and species formation (= speciation) are causally connected. However, empirical tests of "ecological speciation" models are extremely rare. This project evaluates populations of Neochlamisus bebbianae leaf beetles that are associated with different tree species (host plants) in eastern North America. Specifically, it experimentally quantifies the ability of beetle populations associated with different tree species to use each other's host plants and their willingness to mate with each other, and it evaluates patterns of genetic exchange among these populations by collecting DNA sequences and protein polymorphism data. These data are integrated and analyzed at the individual and population levels to test a variety of hypotheses on the diverse genetic and environmental mechanisms by which ecological divergence may drive speciation and biological diversification. Such investigations on speciation ecology are rare yet critical for understanding the origins of Earth's tremendous biodiversity. Because many herbivorous insects (including some Neochlamisus species) are also economic pests, understanding the factors that determine which plants an insect uses, how plants are used, and how new herbivorous insect populations and species form is of applied as well as academic importance. Ecological principles underlying insect-plant relationships are increasingly being used to develop agricultural strategies. The current proposal will provide insights into these principles as well as their consequences for speciation.