Mechanisms of Acacia longifolia invasive success: The role of an Arbuscular Mycorrhizal Fungi

Exotic invasive species are one of the driving-forces of global change that most affects biodiversity. Significant efforts have been devoted to control or eradicate invasive species and restore invaded areas. However, understanding mechanisms underlying invasive success is a pre-requisite for a successful control and restoration strategy. Some recent works stress the importance of plant-soil (including soil micro organisms) interactions in mediating invasion processes. There is some evidence that arbuscular mycorrhizal fungi (AMF) may play a role in invasion processes, namely by interfering in the outcome of the competitive interaction between native and exotic species, promoting the growth of the later and indirectly inhibiting the former. In this work we tested the influence of an AMF, Glomus intraradices, in the outcome of the competitive interaction between Acacia longifolia – an exotic invasive specie introduced in Portuguese coastal sand dunes – and two native N-fixing species: Cytisus sp . and Stauracanthus sp. In semi-controlled conditions, soil composition was manipulated either to include or exclude AMF. Two types of soil were considered to perform this experiment: soil collected under Acacia stand (exotic) and outside Acacia stand (native). Responses to AMF inoculation were species-specific. Acacia and Stauracanthus grew better when inoculated, but only in native soil. Cytisus didn't respond to inoculation. Stauracanthus showed a significantly reduced growth in the presence of Acacia, but only with AMF. On the contrary, Cytisus didn't seem to be affected by Acacia presence, neither with nor without AMF. This results may be taken into account in a possible restoration strategy