Reid's paradox revisited: The evolution of dispersal kernels during range expansion

Benjamin L. Phillips, Gregory P. Brown, Justin M. J. Travis, Richard Shine

Research output: Contribution to journalArticle

193 Citations (Scopus)


Current approaches to modeling range advance assume that the distribution describing dispersal distances in the population (the "dispersal kernel") is a static entity. We argue here that dispersal kernels are in fact highly dynamic during periods of range advance because density effects and spatial assortment by dispersal ability ("spatial selection") drive the evolution of increased dispersal on the expanding front. Using a spatially explicit individual-based model, we demonstrate this effect under a wide variety of population growth rates and dispersal costs. We then test the possibility of an evolved shift in dispersal kernels by measuring dispersal rates in individual cane toads (Bufo marinus) from invasive populations in Australia (historically, toads advanced their range at 10 km/year, but now they achieve 155 km/year in the northern part of their range). Under a common-garden design, we found a steady increase in dispersal tendency with distance from the invasion origin. Dispersal kernels on the invading front were less kurtotic and less skewed than those from origin populations. Thus, toads have increased their rate of range expansion partly through increased dispersal on the expanding front. For accurate long-range forecasts of range advance, we need to take into account the potential for dispersal kernels to be evolutionarily dynamic.

Original languageEnglish
Pages (from-to)S34-S48
Number of pages15
JournalThe American Naturalist
Issue numberS1
Publication statusPublished - Jul 2008


  • climate change
  • Rhinella
  • exotic species
  • introduced species
  • lag phase
  • nonequilibrium
  • toad bufo-marinus
  • cane toads
  • Tropical Australia
  • population spread
  • spatial spread
  • invasion front
  • migration
  • dynamics
  • model
  • speed


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