SG: The ecological and evolutionary consequences of mutualisms for species range expansion

It is a common sight to see bees flitting around flowers during springtime or see several bird species consuming fruits from trees through the year. Although the two events seem unrelated, an underlying phenomenon connects them: namely, that the interacting species benefit each other. In the first case, the bees transport pollen for the flowers thereby dispersing and aiding them in reproduction, and the flowers in turn provide nectar to the bees.

Birds disperse seeds by consuming the fruit (a benefit to them) and defecating the seeds away from the parent plant. This seed dispersal helps trees from competing against their offspring. These bidirectional positive interactions between species are termed mutualisms.

The aim of this project is to develop a mathematical framework to understand how mutualisms impact species dispersal ability in an ecological and evolutionary context. The outcome of this work will help to identify when dispersal should evolve for species participating in a mutualism and how it impacts the spatial spread of the species. The researchers will use their results to foster undergraduate research, implement interdisciplinary teaching modules at the University of Minnesota, and develop management strategies against co-invading mutualistic species.

Although there exists theory on how antagonistic interactions such as predation, competition, or parasitism impact species dispersal, there exists very little on the role of mutualisms. Current theory offers contrasting predictions on whether mutualisms promote or hinder how fast species can disperse into new areas (range expansion). More fundamentally, it is unclear whether and how dispersal ability should evolve for species participating in a mutualism.

This research will therefore set up a mathematical framework that will help determine under what conditions mutualisms (through effects on demography and dispersal) speed up versus slow down range expansion of the participating species. Secondly, the research will test the conditions under which motility is evolutionarily beneficial in a spatially explicit mutualism between two microbial species.

These questions will be addressed through a combination of mathematical models and a tightly controlled microbial experimental system.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.