RangeShifter: a platform for modelling spatial eco-evolutionary dynamics and species' responses to environmental changes

Background/Question/Methods

Rapid environmental changes are threatening biodiversity and exposing species to novel ecological and evolutionary pressures. The scientific community increasingly recognises the need for dynamic models integrating sufficient complexity both to improve our understanding of species’ responses to environmental changes and to inform effective management strategies. We introduce a novel modelling platform, RangeShifter, which integrates complex population dynamics and dispersal behaviour, includes plastic and evolutionary processes, and simulates scenarios on spatially-explicit landscapes. To illustrate the software’s potential we address the key question, 'how do populations spread across patchy landscapes?' Dispersal is a central process in range expansion and while there is a considerable theory on how the shape of a dispersal kernel influences the rate of spread, we know much less about the relationships between emigration, movement and settlement rules and invasion rates. Here, we use RangeShifter to establish how density-dependent emigration and settlement rules interact with landscape characteristics to determine spread rates.

Results/Conclusions

We show that depending on the dispersal behaviour and on the risk of mortality in the matrix, increasing the number of patches does not necessarily maximise the spread rate. This is due to two effects: first, individuals dispersing at the expanding front are likely to exhibit lower net-displacement as they typically do not travel far before finding a patch; secondly, with increasing availability of high quality habitat, density-dependence in emigration and settlement can decrease the number of emigrants and their net-displacement. The rate of spread is ultimately determined by the balance between net travelled distance, the dispersal mortality and the number of dispersing individuals, which in turn depend on the interaction between the landscape and the species’ dispersal behaviour. These results highlight that predicting spread rates in heterogeneous landscapes is a complex task and requires better understanding of the rules that individuals use in emigration, transfer and settlement decisions. We conclude by emphasising that the software provides functionality for a wide variety of modelling applications ranging from applied questions, where it can be parameterised for real landscapes and species to compare alternative potential management interventions, to purely theoretical studies of species’ eco-evolutionary dynamics and responses to different environmental pressures.