Evolutionary Ecology

The effects of ecological and genetic neighborhood size on the evolution of two competing specie

Summary

Individual-based simulations were conducted to examine the effect of a small ecological neighborhood (an area in which ecological processes such as density-dependent factors operate) and the genetic neighborhood size (the size of an area from which the parents may be assumed to be drawn at random) on the coevolution of two competing species. For the simulations, individuals of two consumer species compete for two types of food organisms. Different genotypes (one locus, two alleles) have different efficiencies of food acquisition for different food types. Individual consumer organisms search for foods within their home ranges and reproduce depending on the number of foods eaten. The dispersal distance of the offspring follows a normal distribution with zero mean and sd standard deviation. Simulations were conducted by varying home range size, mating area (area from where individuals choose their mates), standard deviation of dispersal distance, food generation time, the reproductive rates of food populations, and sizes and the number of independent food populations. Food organisms reproduce either within one population or independently within 16 spatially-divided populations.

For all the simulations, competitive exclusion was the most frequent outcome and character displacement was the least frequent outcome. Through a 200-generation simulation, the two consumer species could longer coexist and longer maintain a polymorphic resource use when the home range and mating size were small in 16 spatially-divided populations than when random mating and homogeneous interaction occurred within a community (perfect mixing population). For perfect mixing populations, the frequency of character displacement increased as the food generation time became short and the reproductive rates of food decreased. It follows from the results that the sizes of the genetic and ecological neighborhoods and the mode of resource dynamics can affect the evolution of two competing species.

Keyword: individual-based model, character displacement, local interaction, limited dispersal, coevolution.