Response or Comment
Recently, Schaffer and Tamarin (1973) proposed a model relating changes in reproductive effort (RE) to fluctuating densities in microtine rodents (lemmings and voles). They assumed (and presented data supporting this assumption) that the major effect of increased crowding would be a reduction in survival among prereproductives, thereby lowering the effective fecundity (Schaffer and Rosenzweig 1977) of their parents. As a consequence, Schaffer and Tamarin argued that the optimal reproductive expenditure, E(N), should decline with increasing population size, N. They also deduced the shape of the zero-growth isocline, N*(E), for differing levels of RE and plotted both E(N) and N*(E) on a graph whose axes are reproductive expenditure and population density (Fig1 a).
Original Publication Citation
Gaines, M. S., Schaffer, W. M., & Rose, R. K. (1979). Additional comments on reproductive strategies and population fluctuations in microtine rodents. Ecology, 60(6), 1284-1286. doi:10.2307/1936973
Gaines, Michael S.; Schaffer, William M.; and Rose, Robert K., "Additional Comments on Reproductive Strategies and Population Fluctuations in Microtine Rodents" (1979). Biological Sciences Faculty Publications. 164.