Local adaptation and maladaptation in spatially structured populations

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Most species have populations in many different locations, sometimes separated by areas of poor habitats where few individuals occur. These separate populations are usually at least somewhat genetically different from each other, either by chance (genetic drift) or because different local environments select for different genotypes (local adaptation). Understanding how populations respond to and diverge to these spatially heterogeneous selection pressures is important; for example, populations in warmer environment may be necessary sources of genetic variation to respond to the challenges caused by climate change. In this grant, we will develop new statistical approaches to measure the genomic basis of local adaptation. We will find ways to correct for biases in previous methods caused by uniformly deleterious mutations. Furthermore, both spatially heterogeneous environments and also random increases in the frequency of deleterious mutations at the edge of a species range can slow the rate of expansion of a population over space. Understanding the genetic factors that determine the rate of range expansion is crucial to understanding and protecting biodiversitywhy we see species in the places that the are and not elsewhere, how we can impede the spread of unwanted invasive species, and how we can aid the spread of native species as they move to adjust to climate change. Finally, we will study the causes and consequences of adaptive phenotypic plasticity (which is when the same genotype can develop a phenotype which matches what is required for multiple local environments). We will investigate under which conditions phenotypic plasticity evolves and describe the effects of plasticity on the developmental stability, robustness and evolvability of the species. We hypothesize that different mechanisms of plasticity and the modes of information capture from the environment will qualitatively differ in their efficacy and their effects on robustness. Understanding the ways in which species respond to heterogeneous environments is critical to understanding most aspects of evolutionary biology, and appropriate responses to conservation and climate change challenges depend on such basic science.