Population variability among three small mammal species in the semiarid Neotropics: The role of density-dependent and density-independent factors
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1998
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Abstract
We addressed the role of density-dependent (direct and delayed) and density-independent (precipitation) factors in shaping the dynamics of fluctuating populations of three small mammal species. Using a stepwise regression procedure, we tested the effects of nonlagged population density (log(10)N(t-1)), lagged population density (log(10)N(t-2)), and annual precipitation on the per capita rate of population change of Phyllotis darwini, Akodon olivaceus, and Thylamys elegans in two habitat types of a semiarid region of Chile. The most irruptive species (P. darwini) showed direct and delayed density-dependent effects in equatorial subpopulation, and only direct density-dependence in polar subpopulation. The per capita rates of population change of A. olivaceus showed direct density-dependent and precipitation effects in both habitats types, while T. elegans showed direct density-dependence and precipitation effects in the equatorial subpopulation but only a marginal effect of direct density-dependence in the polar subpopulation. The presence of delayed density-dependent strongly suggests the importance of biological interactions in shaping the dramatic irruptions exhibited by P. darwini.