Metapopulation dynamics as an explanation to the genetic structure of the desert locust populations: parameter exploration.

Abstract

The desert locust is an economically important pest insect which undergoes stochastic boom and bust cycles in population size. During the non-plague periods the desert locust exists in scattered patchy populations which are prone to extinction because of climatic events. Significant genetic divergence between such populations along the Red Sea coast of Eritrea has been reported. A previous study used computer modelling to demonstrate that metapopulation dynamics could produce such divergence despite the homogenisation effect of swarms. The population dynamics were described by a discrete-time logistic model with stochastic switches in the carrying capacity, K, and in the intrinsic growth rate, r, to describe the phase change. The duration of plagues and recession periods were sampled from a normal distribution. The present work is a parameter exploration for this model. The means and standard deviations of the recession and plague durations were the extreme combinations of parameters from the ranges reported in former studies. It is concluded that the recession duration has to be as long as 8-10±2-3 generations and the plague duration half as long but with a variance almost equal to the duration mean to produce genetic divergence of realistic value among the patches.