Evolution at the edge of expanding populations

Maxime Deforet, Carlos Carmona Fontaine, Kirill S. Korolev, Joao B. Xavier

Research output: Contribution to journalArticle

Abstract

Predicting the evolution of expanding populations is critical to controlling biological threats such as invasive species and cancer metastasis. Expansion is primarily driven by reproduction and dispersal, but nature abounds with examples of evolution where organisms pay a reproductive cost to disperse faster. When does selection favor this “survival of the fastest”? We searched for a simple rule, motivated by evolution experiments where swarming bacteria evolved into a hyperswarmer mutant that disperses 100% faster but pays a growth cost of 10% to make many copies of its flagellum. We analyzed a two-species model based on the Fisher equation to explain this observation: the population expansion rate (v) results from an interplay of growth (r) and dispersal (D) and is independent of the carrying capacity: v p 2(rD)1=2. A mutant can take over the edge only if its expansion rate (v2) exceeds the expansion rate of the established species (v1); this simple condition (v2 1 v1 ) determines the maximum cost in slower growth that a faster mutant can pay and still be able to take over. Numerical simulations and time-course experiments where we tracked evolution by imaging bacteria suggest that our findings are general: less favorable conditions delay but do not entirely prevent the success of the fastest. Thus, the expansion rate defines a traveling wave fitness, which could be combined with trade-offs to predict evolution of expanding populations.

Original languageEnglish (US)
JournalAmerican Naturalist
DOIs
StatePublished - Jan 1 2019

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mutants
reproductive cost
swarming
bacterium
bacteria
carrying capacity
flagellum
invasive species
cost
metastasis
cancer
fitness
experiment
image analysis
neoplasms
rate
organisms
simulation
mutant
organism

Keywords

  • Dispersal
  • Evolution
  • Pseudomonas aeruginosa
  • Range expansion
  • Reaction-diffusion model
  • Trade-off

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

Cite this

Evolution at the edge of expanding populations. / Deforet, Maxime; Carmona Fontaine, Carlos; Korolev, Kirill S.; Xavier, Joao B.

In: American Naturalist, 01.01.2019.

Research output: Contribution to journalArticle

Deforet, Maxime ; Carmona Fontaine, Carlos ; Korolev, Kirill S. ; Xavier, Joao B. / Evolution at the edge of expanding populations. In: American Naturalist. 2019.
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