Of the large number of species that are introduced into new habitats, few are successful as invaders. The evolutionary processes that allow some species to invade while others do not are poorly understood. The evolutionary potential (evolvability) of populations might affect the ability to invade novel habitats. Evolvability depends on existing genetic variation in a population on which natural selection could act. This study will compare differences in evolvability between invasive and noninvasive populations within a crustacean species. The small crustacean, Eurytemora affinis, repeatedly has invaded fresh water habitats from saltwater habitats. These invasions were accompanied by evolutionary shifts in osmotic tolerance. The source populations would have required sufficient genetic variance for osmotic tolerance to survive the transition into fresh water. This study tests the importance of two main forces that could generate and maintain genetic variance: the tendency of traits to vary due to new mutations, and the effect of fluctuating selection on the maintenance of genetic variation (such as seasonal fluctuations in salinity). This study also examines patterns of genetic dominance for saltwater and freshwater tolerance, and how dominance varies across habitats.
Invasive species pose major threats to ecosystem integrity and public health. By better understanding the mechanisms that allow a species to invade, we can improve our ability to control such invasions.
