Since the hallmark papers of Ken Cullings et al. (1996) and Martin Bidartondo et al. (2002) – both in Nature – many studies have reported on the high mycorrhizal specificity of mycoheterotrophic plants. But specificity is a relative thing, and may differ over the geographic distribution of a species. Therefore Sofia Gomes compared the mycorrhizal specificity of several Thismia species in Australia and New Zealand with that of surrounding plants. She found that mycoheterotrophs always chose for a very specific lineage of fungi, unlike green plants for which mycorrhizal interactions are much less specific. The results were recently published in the journal New Phytologist.
http://onlinelibrary.wiley.com/doi/10.1111/nph.14249/full