The Genetic Effects of Ecological Disturbance: Flooding in Jumping Mice

Pacific jumping mice (Zapus trinotatus) live in riparian habitats that are discontinuously distributed and subject to regular flooding. Both of these characteristics have a spatial component. Habitat-restricted dispersal frequently leads to spatial genetic structure among individuals, and flooding often imposes spatially specific mortality. Here I report that following a severe flood, an interaction between these factors resulted in an immediate reduction of genetic diversity and genetic divergence of the postflood population. Survival was spatially biased toward more closely related individuals, and this was propagated throughout the postflood population by changes in reproduction. Not only did the number of closely related breeding pairs increase, but so did the production of offspring by individuals. These changes precipitated strong genetic effects, including a reduction in observed heterozygosity, an increase in relatedness, a doubling of inbreeding levels, and significant genetic divergence from previous years.