Myrtaceae: VAM occur in more genera than ectomycorrhizas.

ALLAWAY, WILLIAM¹, SKYE STEVENS² & ANNE ASHFORD².

¹School of Biological Sciences, The University of Sydney, NSW 2006, AUSTRALIA. ²School of Biological Science, UNSW, Sydney 2052, AUSTRALIA.

Myrtaceae are important in Australian vegetation, and members of the family occur in a wide range of environments from rainforest to semi-arid. The family is often considered to be predominantly ectomycorrhizal - a view, however, which is largely based on the eucalypts. Although there is increasing evidence that VAM occur widely in the family, this has not been systematically evaluated. We investigated the incidence of VAM and ectomycorrhizas in myrtaceous species representing as wide a range of genera as possible. We collected 48 species, from 9 localities in New South Wales (eastern Australia) and 7 localities in Western Australia. Only roots that could be traced back to the bole of an identified plant were collected. We combine our data with a survey of the literature to provide a more comprehensive picture. In the Myrtaceae overall, only 2 genera had ectomycorrhizas but no VAM detected on them, while in 16 genera VAM only were detected. Both ectomycorrhizas and VAM were found in 17 genera, and in one genus no mycorrhizal structures were found. Organized by genera, results of our survey (S) and from the literature (L) were strikingly similar, viz. ectomycorrhizas only found 2S, 2L; VAM only found 14S, 10L; both types 9S, 9L; no mycorrhizas found 1S. Thus, when the numerical superiority of eucalypt species in surveys is eliminated the family no longer seems mainly ectomycorrhizal, but rather slightly biased towards VAM. We discuss these results in the contexts of the taxonomy and biogeography of the family.