Contrasting mycorrhizal growth responses in native and invasive woody species are associated with distinct root trait syndromes

1. Invasive plant species often express resource-acquisitive leaf traits that support rapid growth, but associated fine root traits and the role of microbial mutualists in invader whole-plant functioning remain poorly understood. 2. We performed an experiment of 12 phylogenetically grouped native and non-anative, invasive woody species, grown with or without a common inoculum of arbuscular mycorrhizal fungi (AMF) across two nutrient levels. We measured 10 fine root traits associated with nutrient uptake and suitability of AMF colonization. 3. The presence of AMF increased the growth rate of all species, but native species were significantly more dependent on AMF than invaders. Furthermore, invaders expressed a distinct syndrome of first-order root traits, including longer, thinner roots of high specific root length, greater branching intensity and lower tissue density, which are traits associated with rapid nutrient uptake and low AMF association. This syndrome was independent of phylogeny, AMF inoculation and soil fertility. 4. An acquisitive fine root trait syndrome for invaders supports high photosynthetic and growth rates, linking above-and below-ground functioning. The occurrence of this syndrome across phylogenetic groups indicates that lineages of woody invaders typically associated with arbuscular mycorrhizas may be generally less dependent on AMF than native species.