Discounting initial population sizes for predicting extinction probabilities in patchy environments


Jianguo "Jack" Liu

Journal or Book Title: Ecological Modelling

Volume/Issue: 70

Page Number(s): 51-61

Year Published: 1993


Extinction is a major concern in conscrvation. A most urgent need is to predict the relationship of a population's initial size to its probability of extinction. Previous work has led to a widely accepted conclusion that the larger an initial population size, the less likely the population will go extinct. I used a spatially-explicit simulation model to investigate extinction probabilities of Bachman's Sparrow (Aimophila aestivalis) in patchy environments. Contrary to the conventional wisdom, I found that the relationship between extinction probabilities and initial population sizes of the sparrows was not correlated when initial individuals were in several patch types. To make good predictions of the sparrows' extinction rates, I have suggested discounting models which incorporated initial population sizes and initial spatial distributions. The models discounted initial population sizes on the basis of patch characteristics (patch suitability, timing of patch suitability, and duration of patch suitability). As a result, the extinction probabilities decreased with the logarithm of discounted population sizes. The discounting models may have implications for quantitative predictions of extinction chances of other species, since most environments are patchy or spatially-subdivided. The discounting approach may be also useful for evaluating impacts of patchy environments on population dynamics and community structure.

Type of Publication: Journal Article