Poster #11

Why are some invasive species so successful in nutrient-impoverished habitats in south-western Australia: a perspective from their phosphorus-acquisition strategies
D TANG, L YAN, J. L. FISHER, H.B KANG, P DALLONGEVILLE, J WASAKI, X WANG, H LAMBERS
School of Biological Sciences, University of Western Australia, Perth, WA 6009, Australia

Invasive plants are a major cause of the global biodiversity crisis; it is therefore essential to understand the mechanisms that explain why invasives are successful. South-western Australia is a global biodiversity hotspot with very low soil phosphorus (P) concentrations. Here, a large proportion of native plants release carboxylates that mobilise soil P while also exhibiting high leaf manganese concentrations ([Mn]), a proxy for rhizosphere carboxylates. Most widespread invasive species in south-western Australia are arbuscular mycorrhizal. We hypothesised that some of these species have similar P-acquisition strategies as native carboxylate-releasing P-mobilising species in P-impoverished soils. We selected 23 common invasive species in the field and measured their leaf [Mn], relative to that of native reference species, to proxy their carboxylate release while growing seven of these in hydroponics with different P supply to measure root carboxylate exudation. We also measured leaf P concentration and photosynthetic P-use efficiency. Almost all invasive species had higher leaf [Mn] than the negative reference species (no carboxylate release). All glasshouse-grown species that showed a high leaf [Mn] in the field released carboxylates when grown at low P supply, with slower rates at higher P supply. Invasive AM species released root carboxylates as a P-acquisition strategy, which very likely allows them to successfully invade severely P-impoverished habitats.