Résumé
Fungal invasions are increasingly recognized as a significant component of
global changes, threatening ecosystem health and damaging food production.
Invasive fungi also provide excellent models to evaluate the generality of
results based on other eukaryotes. We first consider here the reasons why
fungal invasions have long been overlooked: they tend to be inconspicuous,
and inappropriate methods have been used for species recognition. We then
review the information available on the patterns and mechanisms of fungal
invasions. We examine the biological features underlying invasion success
of certain fungal species. We review population structure analyses,
revealing native source populations and strengths of bottlenecks. We
highlight the documented ecological and evolutionary changes in invaded
regions, including adaptation to temperature, increased virulence,
hybridization, shifts to clonality and association with novel hosts. We
discuss how the huge census size of most fungi allows adaptation even in
bottlenecked, clonal invaders. We also present new analyses of the
invasion of the anther-smut pathogen on white campion in North America, as
a case study illustrating how an accurate knowledge of species limits and
phylogeography of fungal populations can be used to decipher the origin of
invasions. This case study shows that successful invasions can occur even
when life history traits are particularly unfavourable to long-distance
dispersal and even with a strong bottleneck. We conclude that fungal
invasions are valuable models to contribute to our view of biological
invasions, in particular by providing insights into the traits as well as
ecological and evolutionary processes allowing successful introductions.