Results/Conclusions: Almost all Proteaceae produce carboxylate-releasing cluster roots, which are capable of mobilising scarcely available phosphorus and micronutrients, including manganese. They effectively ‘mine’ these nutrients, as opposed to ‘scavenging’ them from the soil solution further away from the root surface, as mycorrhizas do. In addition to efficient acquisition of phosphorus from soil, south-western Australian Proteaceae species also use the acquired phosphorus very efficiently in photosynthesis, show a tremendous capacity to remobilise phosphorus from senescing leaves, and contain a large amount of phosphorus in their seeds. The traits referred to here help explain the ecological success of non-mycorrhizal species on severely phosphorus-impoverished soils in south-western Australia and elsewhere. These same traits may also have allowed non-mycorrhizal families to diversify in these severely nutrient-impoverished environments.
A very exciting question that remains to be explored further is why species with a superior phosphorus-acquisition strategy coexist with ones that are less effective at acquiring soil phosphorus. We have evidence that facilitation plays a role, and that nutrients mobilised by 'mining' species are also used by neighbours that lack this strategy. In addition, there is evidence that a trade-off exists between efficient phosphorus acquisition and pathogen susceptibility, i.e. species with ephemeral carboxylate-releasing roots are poorlt defended against pathogens, especially oomycetes. Future research will explore this in greater detail.