Data from: Evolution transforms pushed waves into pulled waves

Understanding the dynamics of biological invasions is crucial for managing
numerous phenomena, from invasive species to tumours. While the Allee
effect (where individuals in low-density populations suffer lowered
fitness) is known to influence both the ecological and evolutionary
dynamics of an invasion, the possibility that an invader's
susceptibility to the Allee effect might itself evolve has received little
attention. Since invasion fronts are regions of perpetually low population
density, selection should be expected to favour vanguard invaders that are
resistant to Allee effects. This may not only cause invasions to
accelerate over time, but, by mitigating the Allee effects experienced by
the vanguard, also make the invasion transition from a pushed wave,
propelled by dispersal from behind the invasion front, to a pulled wave,
driven instead by the invasion vanguard. To examine this possibility, we
construct an individual-based model in which a trait that governs
resistance to the Allee effect is allowed to evolve during an invasion. We
find that vanguard invaders evolve resistance to the Allee effect, causing
invasions to accelerate. This results in invasions transforming from
pushed waves to pulled waves, an outcome with consequences for invasion
speed, population genetic structure, and other emergent behaviours. These
findings underscore the importance of accounting for evolution in invasion
forecasts, and suggest that evolution has the capacity to fundamentally
alter invasion dynamics.