Plants and animals adapted to colonize disturbed sites might also be better invaders, but this phenomenon has not been widely
considered in fungi. We investigated genetic diversity and structure amongst isolates of Neofusicoccum parvum, N. cordaticola, N.
kwam-bonambiense and N. umdonicola that coexist sympatrically on a native tree, Syzygium cor-datum, across its distribution in
South Africa. Species composition varied among stands, with dominance of N. parvum in disturbed stands, and absence in
undisturbed stands, where the other species dominated. N. parvum populations from trees planted in urban environments were
more genetically diverse than populations from human disturbed stands of S. cordatum. Bayesian analysis clustered N.
parvum isolates in three sub-populations, suggesting three sources of origin. These results support the hypothesis that as a
generalist N. parvum will dominate human disturbed sites and trees in urban areas, indicating strong potential for invasion, and
its spreading from non-native hosts to native S. cordatum, rather than vice versa.