€-logistic Model
Slide 44 of 47
The distinction between the 2 models can be very important. In the first, the rate of change of the birth and death rates with population size is linear, i.e., the classic logistic population growth model. In the second, the change can be very nonlinear. As a result, the €-logistic model can cause populations to be very persistent, or very extinction prone, depending on the shape of the function. In Fig. 7, the curve for per capita recruitment with €€=€10 will result in a population with much greater persistence than the curve with €€=€0.1 because as the population size becomes small, the € = 10 population will be at peak reproduction for populations <60, whereas peak reproduction is only reached at a population size of zero for the €="0.1" population. Fowler (1981, 1994) argues that both theory and empirical information support the conclusion that most density-dependent change occurs at high population levels (close to the carrying capacity) for species with life history strategies typical of large mammals, such as deer (€€> 1). The reverse is true for species with life history strategies typical of insects and some fishes, with € <1).
