Developmental and Genetic Basis of Life History Variation along a Speciation Continuum

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As scientists try to predict how populations will respond to rapid environmental change, it is becoming increasingly important to understand the genetic basis of adaptation and speciation. The role played by phenotypic plasticity (i.e., the ability of a single genotype to produce different phenotypes under different environmental conditions) is also important. Phenotypic plasticity can provide an immediate population-wide response to new or changing conditions, but how such environmentally-induced phenotypes lead to speciation (how they eventually become genetically fixed) is less clear. The proposed research will therefore test the relative importance of genetic and environmental factors (i.e., nature versus nurture) at different stages of evolution, using lampreys as a model system. Lampreys are ancient vertebrates which exhibit a rich diversity of life history types: they may feed parasitically on other fishes either at sea or in fresh water or, even more dramatically, may bypass the adult feeding phase altogether and reproduce at small sizes in their home streams. Some nonparasitic species are genetically distinct from their parasitic ancestor; in other cases, different migratory and feeding types show little or no genetic differentiation (i.e., represent the early stages of divergence). It appears that a single species may produce different life history types, but whether this is due to genetic polymorphism or phenotypic plasticity is unknown. The proposed research will be the first to test this, using complementary developmental (e.g., rearing offspring of different feeding types under common laboratory conditions) and genetic approaches. Understanding the basis of life cycle diversity has significant management implications (e.g., understanding what enabled the sea lamprey to become invasive in the Great Lakes). Being able to predict under what conditions invasion of fresh water systems could happen again is particularly important in the context of expected climate-driven changes to the relative productivity of marine and freshwater systems. This research will provide students with training in cutting-edge genomic technologies, producing personnel highly qualified for employment in research and development in academia and industry.