Eco-evolutionary dispersal dynamics under climate change

Background/Question/Methods

A growing body of theory explores the causes and consequences of dispersal evolution at expanding ranges. Selection pressures acting on dispersal are likely to be very different at an expanding range margin than in the core or the margins of a stationary range. Typically, model results lead to the prediction that dispersal will evolve upwards during range expansion, and there is a suggestion that this can drive faster invasion rates and, in the context of climate change, can promote evolutionary rescue at a macroecological scale. To date, most theory has explored either the evolution of a density independent emigration rate or the evolution of a passive dispersal kernel. Here, we argue that a greater understanding of the eco-evolutionary dynamics of dispersal during range expansion requires a more mechanistic treatment of dispersal.

Results/Conclusions

 We show recent results obtained using models that have been developed to incorporate greater realism. Amongst these, some key findings are:

 1. Selection on a context-dependent emigration rule results in strategy where emigration occurs at much lower local population densities at an advancing front than is the case in a stationary range.

2. Riskier movement behaviour may evolve during range expansion, resulting in greater dispersal mortality but in increased achieved dispersal distances and faster rates of spread.

3. When range expansion occurs into an area occupied by a competitor, a major constraint may be placed on the upwards evolution of dispersal due to trade-offs with other life history traits.  

In conclusion, we emphasise a need to focus on the three key stages of dispersal; emigration, transfer and settlement. Additionally, more theory is required exploring eco-evolutionary dispersal dynamics across shifting environmental gradients (rather than the pure invasion scenarios that are typically studied) and these should investigate the patterns and dynamics not only at the front of an expanding range, but also in the core and retreating margin.  Extending this approach to include multiple species and their interactions, thus gaining a metacommunity perspective on dispersal evolution would be a further valuable advance.