“Dirt-poor soils, pesky parasites and friendly fungi shape plant diversity in south-western Australia” Hans Lambers

Southwest Australia is a biodiversity hotspot, with greatest plant diversity on severely phosphorus-impoverished soils. Non-mycorrhizal plant families (e.g., Proteaceae) feature prominently on the poorest soils, and are uncommon on richer soils.

Almost all Proteaceae produce cluster roots, which mobilise scarcely available phosphorus. Australian Proteaceae also use phosphorus very efficiently in photosynthesis, and show a tremendous capacity to remobilise it from senescing leaves. These traits explain their ecological success on impoverished soils.

Why do species with a superior phosphorus-acquisition strategy coexist with ones that are less effective? Facilitation by neighbours definitely plays a role, and nutrients mobilised by Proteaceae are also used by neighbours without this strategy. It is only part of the story, however, and native parasites (oomycetes or water-moulds) also contribute to the megadiversity in the southwest.