The Evolutionary Dynamics of a Dormant Egg Pool

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The dormant life-history stages of many organisms, including most terrestrial plants, many terrestrial and freshwater invertebrate animals, and even a few vertebrates, represent a storage of species and genetic diversity. When environments change through time, these resistent stages (typically though not always seeds and eggs) prevent extinction of those types of organisms that could not withstand the change in their active states. This research explores a series of questions about how dormant stages affect survival and maintenance of variation in the presence of a changing environment. The work combines development of new mathematical theory with the use of a species of lake-inhabiting crustacean copepods (ca. 1 mm long) as a model system. It is one for which considerable information is already known. Four major questions will be addressed: (1) What is the environmental and physiological basis for the long-term dormancy, (2) Does a temporally-fluctuating environment combined with long- term dormancy provide a mechanism for maintaining greater variation than would otherwise occur, (3) How do sediment processes (mixing, settling, mortality of dormant stages) affect the distribution of variable stages, and (4) Can observations already made on the copepod population in question be explained through an understanding of storage of dormant stages? The research involves a combination of field sampling of lake sediments, rearing of copepods in the laboratory, and a careful matching of mathematical theory with known processes. Theory will be generalized after its application to the copepod system is established. Current predictions are for climates to become both drier in the northeastern US and to become more variable. Understanding how species with dormant stages are likely to respond to these changes will help guide predictions of changes in plant and animal abundance and distribution.