PT  - JOURNAL ARTICLE
AU  - Emanuel A. Fronhofer
AU  - Sereina Gut
AU  - Florian Altermatt
TI  - Evolution of density-dependent movement during replicated experimental range expansions
AID  - 10.1101/114330
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 114330
4099  - http://biorxiv.org/content/early/2017/03/06/114330.short
4100  - http://biorxiv.org/content/early/2017/03/06/114330.full
AB  - Range expansions and biological invasions are prime examples of non-equilibrium systems that are likely impacted by rapid evolutionary changes. As a spatial process, range expansions are driven by dispersal and movement behaviour. While it is widely accepted that dispersal and movement may be context-dependent, for instance density-dependent, and best represented by reaction norms, the evolution of density-dependent movement during range expansions has received very little experimental attention. We therefore tested current theory predicting the evolution of density-independent movement at range margins using highly replicated and controlled range expansion experiments with 14 genotypes of the protist model system Tetrahymena thermophila. Although rare, we found evolutionary changes during range expansions even in the absence of initial standing genetic variation. Range expansions led to the de novo evolution for completely density-independent movement at range margins and a positive density-dependent movement reaction norm in range cores. In addition, we report the evolution of increased reproductive rates at range margins and slightly increased competitive ability in range cores. Our findings highlight the importance of understanding dispersal as an evolving reaction norm and a plastic life-history trait of central relevance for range expansions, biological invasions and the dynamics of spatially structured systems in general.