M. Doebeli et Gd. Ruxton, EVOLUTION OF DISPERSAL RATES IN METAPOPULATION MODELS - BRANCHING ANDCYCLIC DYNAMICS IN PHENOTYPE SPACE, Evolution, 51(6), 1997, pp. 1730-1741
We study the evolution of dispersal rates In a two parch metapopulatio
n model. The local dynamics in each patch are given by difference equa
tions, which, together with the rate of dispersal between the patches,
determine the ecological dynamics of the metapopulation. We assume th
at phenotypes are given by their dispersal rate. The evolutionary dyna
mics in phenotype space are determined by invasion exponents, which de
scribe whether a mutant can invade a given resident population. If the
resident metapopulation is at a stable equilibrium, then selection on
dispersal rates is neutral if the population sizes in the two patches
are the same, while selection drives dispersal rates to zero if the l
ocal abundances are different. With non-equilibrium metapopulation dyn
amics, non-zero dispersal rates can be maintained by selection. In thi
s case, and if the patches are: ecologically identical, dispersal rate
s always evolve to values which induce synchronized metapopulation dyn
amics. If the patches are ecologically different, evolutionary branchi
ng into two coexisting dispersal phenotypes can be observed. Such bran
ching can happen repeatedly, leading to polymorphisms with more than t
wo phenotypes. If there is a cost to dispersal, evolutionary cycling i
n phenotype space can occur due to the dependence of selection pressur
es on the ecological attractor of the resident population, or because
phenotypic branching alternates with the extinction of one of the bran
ches. Our results extend those of Holt and McPeek (1996), and suggest
that phenotypic branching is an important evolutionary process. This p
rocess may be relevant for sympatric speciation.