Abstract
The speed at which biological range expansions occur has important consequences for the conservation management of species experiencing climate change and for invasion by exotic organisms. Rates of dispersal and population growth are known to affect the speed of invasion, but little is known about the effect of having a community of dispersal phenotypes on the rate of range expansion. We use reaction-diffusion equations to model the invasion of a species with two dispersal phenotypes into a previously unoccupied landscape. These phenotypes differ in both their dispersal rate and population growth rate. We find that the presence of both phenotypes can result in faster range expansions than if only a single phenotype were present in the landscape. For biologically realistic parameters, the invasion can occur up to twice as fast as a result of this polymorphism. This has implications for predicting the speed of biological invasions, suggesting that speeds cannot just be predicted from looking at a single phenotype and that the full community of phenotypes needs to be taken into consideration.
Highlights
There is evidence that species are expanding their range as a result of climate change and due to accidental or deliberate introductions of exotic organisms [1,2,3,4]
We have investigated the effect of the presence of two dispersal phenotypes on a species’ invasion speed
If the morphs differ in both their dispersal ability and growth rate, the invasion speed can be faster than the speed of either morph on its own
Summary
There is evidence that species are expanding their range as a result of climate change and due to accidental or deliberate introductions of exotic organisms [1,2,3,4]. The rate of spread of exotic species as a result of introductions can be important especially if these species become pests [7]. Developments since Fisher have found that many factors including Allee effects, timing of reproduction and dispersal in the life cycle and environmental heterogeneity can influence the speed of invasion (reviewed in [9]). Adaptation to local conditions has been found to influence the rate of spread. Garcıa-Ramos and Rodrıguez found that in a spatially heterogeneous environment the rate of local adaptation can be the key limiting factor to spread, with faster range expansions occurring when the environmental gradient is shallower [10]
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