The importance of the community context for understanding eco-evolutionary dynamics: Insights from experimental and theoretical range expansions

Background/Question/Methods

Understanding and predicting the ecological and evolutionary dynamics of range expansions and biological invasions is of great ecological and economical interest. While theoretical work has advanced significantly over the last years, some of the most basic predictions concerning evolutionary changes during range expansions and their feedbacks on ecological dynamics and patterns remain to be tested experimentally.

Central predictions that remain to be tested include that range expansions select for increased dispersiveness at range margins, that population density decreases from range core to range margin due to trade-offs between dispersal and competitive ability and that invasions into fitness-relevant gradients will lead to stable range borders, to name a few examples.

In order to provide causal evidence in favour or against these predictions we studied range expansions experimentally using microcosm landscapes and protists as model organisms.

Results/Conclusions

While we find that range expansions indeed select for increased dispersal at range margins we do not find that population densities decrease from range cores to ranges margins. We also find that invasion dynamics are disturbingly insensitive to gradients in local mortality.

Our results show that a number of theoretical predictions concerning rapid evolutionary changes during range expansions do not hold true, even in simple microcosm landscapes. We link these erroneous predictions to the fact that the community context is typically ignored in current range theory. We show that including the community context, specifically the resource dynamics, allows us to explain our findings.