Causes of range limits – an evolutionary perspective

Yvonne Willi

University of Basel, Switzerland

yvonne.willi@unibas.ch

Species range limits, when not caused by dispersal limitation, are a reflection of limits to the ecological niche. Therefore, while the main challenge of understanding distribution limits for ecologists is to define the parameter space that encompasses the niche, evolutionary ecologists face a much larger problem. They need to explain why niche evolution is constrained in general, and at range margins in particular. Both aspects are unresolved, and count among the major gaps of knowledge in evolutionary ecology.

Ecological studies document that most range limits are associated with a change in climatic conditions. In contrast, several evolutionary factors may be involved in constraining the expansion of the climate niche, and their importance depends on the steepness of the gradient relative to the geographic scale. Our research shows that on a geographic scale, past range expansion associated with genetic drift and mutation accumulation seem to dominate as the causative factor for range limits. In contrast, for elevational range limits, genetic trade-offs seem more relevant. I will present results on the causes of range limits on these two scales.

Recent publications:

1 Willi, Y., Fracassetti, M., Bachmann, O. & Van Buskirk, J. 2020 Demographic processes linked to genetic diversity and positive selection across a species range. Plant Communications, in press.

2 Perrier, A., Sanchez-Castro, D. & Willi, Y. 2020 Expressed mutational load increases towards the edge of a species’ geographic range. Evolution 74, 1711–1723.

3 Walden, N., Lucek, K. & Willi, Y. 2020 Lineage-specific adaptation to climate involves flowering time in North American Arabidopsis lyrata. Molecular Ecology 29, 1436–1451.