Dispersal, Population Regulation, and K-Selection in Field Mice

Abstract

The beach vole Microtus breweri on Muskeget Island, Massachusetts [USA], does not undergo regular density fluctuations, as do most other microtine rodents. The island is 2.6 km2 in size, with both good and poor habitat. In addition, the voles are relatively K-selected, as compared with mainland control populations of the meadow vole M. pennsylvanicus. To explain the lack of cycles in the beach vole, a continuum model whereby the degree of cycling is related to the degree of dispersal was developed. It is postulated that predation is a measure of dispersal. The lack of a cycle on the island suggests that dispersal is selective and supports the argument that cycles are driven by a regularly changing genetic composition of the population. Dispersal is measured by predation and is a selective process. Other continua should fit the dispersal continuum, and data are presented to show that the r-K continuum does fit. Ways to test the model are suggested.