Evol Ecol Res 7: 943-971 (2005)     Full PDF if your library subscribes.

Agent-based models of competitive speciation I: effects of mate search tactics and ecological conditions

Rainer Hilscher

Informatics Department, Evolutionary and Adaptive Systems Group, University of Sussex, Falmer, Brighton BN1 9RH, UK

e-mail: rainerh@sussex.ac.uk


Aims: To understand competitive speciation dynamics of an initially monomorphic and randomly mating population under different ecological conditions (different food resource distributions) and different competition scenarios (competition between specialist, intermediate and generalist individuals). To compare the speciation potential of two female mate-search tactics (best-of-n and threshold).

Model: Generational agent- (or individual-) based simulation model with male and female individuals; polygynous mating system with explicit leks and two different female mate-search tactics; explicit modelling of food resource; explicit implementation of an ecological range variable (αeco) determining the range of food objects individuals of a given phenotype can eat (and thus the competition between individuals).

Key variables: Individuals in one-trait experiments are characterized by a phenotype consisting of two traits, Teco (defines preferred mates for females and preferred food objects for all individuals) and Tmate-range (defines the degree of assortative mating of females). In two-trait experiments, females select mates according to Tmate (a mating trait independent of Teco).

Conclusions: Given a one-trait system, a population can undergo competitive speciation to completion. New species occupy niches located anywhere in the environment and not just in the extreme regions; species constellations are determined by (αeco). Given a spatially explicit ecological gradient model, populations do not speciate in geographical space; thus neighbouring individuals constantly compete. Best-of-n mating usually promotes speciation better than threshold mating. Speciation may also occur in a two-trait system, although in such a case assortative mating has to evolve also. Such speciation depends on a more restricted set of parameter values than does the one-trait case.

Keywords: agent-based model, assortative mating, competition, individual-based model, mating strategy, niche width, sympatric speciation.

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