Boom-bust population dynamics drive rapid genetic change

Loss of genetic diversity can reduce the evolutionary potential of declining populations, affecting their ability to respond to environmental change. This is particularly relevant given the rapid environmental changes arising from human activity. Species that naturally experience extreme booms and busts in population size provide an opportunity to investigate how genetic diversity can be maintained in populations subject to repeated episodes of population decline. Our 13-y study reveals that stable population dynamics and boom-bust population dynamics maintain genetic variation under extreme environmental fluctuations: One of our study species conserved genetic diversity by maintaining a relatively stable population size, while for a second species, gene flow during periodic booms was sufficient to maintain genetic diversity despite repeated and prolonged population crashes.