Evol Ecol Res 7: 973-992 (2005) Full PDF if your library subscribes.
Dispersal evolution in fragmented habitats: the interplay between the tendency and the ability to disperse
Roman Yukilevich
Department of Ecology and Evolution, State University of New York at Stony Brook, Stony Brook, NY 11794-5245, USA
e-mail: yukilevi@life.bio.sunysb.eduABSTRACT
Questions: How will two dispersal traits, one determining dispersal ability and the other determining dispersal tendency, affect each other’s evolutionary dynamics in a fragmented landscape? Which properties of fragmented habitats lead to evolutionary interactions between these two traits and which allow the traits to evolve independently?
Mathematical method: A population genetic model with explicit ecological costs. The mean fitness of the population is maximized on S. Wright’s adaptive topography.
Key assumptions: Two haploid (or diploid) loci, each with two alleles. The first locus describes dispersal ‘tendency’, where the strength of environmental fluctuations and the distance separating suitable habitats determines the cost of sedentary behaviour relative to the cost of dispersal. The second locus determines dispersal ‘ability’, where there is a trade-off between survival in the local habitat (favouring low dispersal ability type) and survival during a dispersal event (favouring high dispersal ability type).
Conclusions: The evolutionary relationships between these dispersal traits range from simple monotonic trajectories, where the traits evolve independently, to non-linear dynamics, where the evolution of one trait strongly depends on the other’s evolution. One example of non-linearity: the same ecological conditions may either allow the fixation or the loss of dispersal traits simply depending on the initial allelic frequencies of dispersal traits. This result leads to a novel colonization bias hypothesis. Non-linear dynamics are found when habitats have intermediate levels of environmental fluctuation and/or when the distance between habitats is large and when dispersal tendency has high genetic penetrance (sensu Falconer, 1981). When dispersal tendency and ability traits exhibit non-linear dynamics, our view of their evolution will be seriously distorted if both are not studied simultaneously.
Keywords: adaptive landscape, co-evolution, colonization, evolutionary dynamics, islands, penetrance.
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