Patterns and processes of population dynamics with fluctuating habitat size: a case study of a marine copepod inhabiting tide pools

Abstract

The logistic model is a fundamental population model often used as the basis for analyzing wildlife population dynamics. In the classic logistic model, however, population dynamics may be difficult to characterize if habitat size is temporally variable because population density can vary at a constant abundance, which results in variable strength of density-dependent feedback for a given population size. To incorporate habitat size variability, we developed a general population model in which changes in population abundance, density, and habitat size are taken into account. From this model, we deduced several predictions for patterns and processes of population dynamics: (1) patterns of fluctuation in population abundance and density can diverge, with respect of their correlation and relative variability; and (2) along with density dependence, habitat size fluctuation can affect population growth with a time lag because changes in habitat size result in changes in population density. In order to test these predictions, we applied our model to population dynamics data of 36 populations of Tigriopus japonicus, a marine copepod inhabiting tide pools of variable sizes caused by weather processes. As expected, we found a significant difference in the fluctuation patterns of population abundance and density of T. japonicus populations with respect to the correlation between abundance and density and their relative variability, which correlates positively with the variability of habitat 3 size. In addition, we found direct and lagged-indirect effects of weather processes on population growth, which were associated with density dependence and impose regulatory forces on local and regional population dynamics. These results illustrate how changes in habitat size can have an impact on patterns and processes of wildlife population dynamics. We suggest that without knowledge of habitat size fluctuation, measures of population size and its variability as well as inferences about the processes of population dynamics may be misleading.4

Spatial optimization of invasive species control informed by management practices

“…We considered the five environmental variables (i.e., paddy field area, dry crop fields, slope, road extension density, and flow accumulation, described above) and the capture effort in each section as linear predictors that potentially influence the population growth rate. The logarithm of the relative density of turtles is described as follows (Colchero et al 2009, Fukaya et al 2013, Fukasawa et al 2013 b ):where is an intercept and λ is the density dependence on the logarithmic relative density in the next year. Density dependence is absent when = 1.…”

“…We considered the five environmental variables (i.e., paddy field area, dry crop fields, slope, road extension density, and flow accumulation, described above) and the capture effort in each section as linear predictors that potentially influence the population growth rate. The logarithm of the relative density of turtles μ i,t is described as follows (Colchero et al 2009, Fukaya et al 2013, Fukasawa et al 2013b:…”