Evolutionary dynamics of dispersal during co-invasion of trees and their mycorrhizal symbionts and pathogens

Abstract

Most invasive trees depend closely on mycorrhizal symbionts to provide required resources, and thus their invasive success depends on the dispersal of these symbionts as well as their own dispersal. Invasive trees may also be negatively impacted by pathogenic fungi in their natural range, and thus benefit from ‘enemy release’ if they spread into new areas faster than these pathogenic fungi. Previous empirical and theoretical work has shown that the dispersal characteristics of organisms can undergo selection pressure and evolution during the course of an invasion or colonization of new areas, but the evolutionary dynamics of dispersal during coinvasion has not been considered. In this work, we use spatially-explicit eco-evolutionary simulation modelling to investigate how the dispersal characteristics of trees and their mycorrhizal symbionts and pathogens evolve over the course of a tree invasion. We find that the selection pressures manifesting during the invasion cause the dispersal characteristics of the different organisms to vary across time and space in complex and interdependent ways that are influenced by human management. For example, dispersal ability of the three organisms increases over time and is higher at the fronts of an invasion, but managing trees through removal of outliers decreases the rate at which increased dispersal ability evolves.