A project undertaken at The Royal Botanic Gardens Victoria, and supervised by Dr Naveed Davoodian.
Mesophelliaceae is a family of mycorrhizal, truffle-like fungi endemic to Australia. They are critical elements of ecosystems wherever Eucalyptus occur, exchanging nutrients with these plants as well as serving as food sources for a number of Australian mammals. Like many fungi, the breadth and depth of the diversity, ecology and evolutionary relationships of Mesophelliaceae has yet to be fully ascertained. Our study has helped make several leaps forward in our understanding of Mesophelliaceae. As with previous studies, we found multiple well-supported evolutionary groupings based on morphology, and inferred the Mesophelliaceae to have emerged fairly recently (less than 25 million years ago) based on molecular clock analysis. We found the “aggregatum group” (species which form numerous small sporocarps in close proximity) to be the most ancestral lineage within Mesophelliaceae, a novel result not inferred in previous studies.
A recently collected specimen of Mesophelliaceae from New South Wales.
Many lineages of Mesophelliaceae are morphologically, and apparently chemically, unique and as such posed challenges when conducting laboratory work. For instance, the “gummy group” (species with sporocarp texture like chewed bubble gum) yielded viscous DNA extracts that interfered with DNA sequencing flow cells, despite numerous attempts to clean the DNA extracts. Some portions of the genomes sequenced occurred as multiple distinct copies, complicating phylogenetic inference in a few cases. This poses challenges for the generation of DNA barcodes, as the ITS region can also occur as multiple intragenomic variants. Long-read sequencing assisted us in visualising the variation within species in order to adequately characterise the ITS region.
Future studies will focus on the “powdery-spored group” (species with powdery spores) to clarify relationships therein and provide insights into the ecology and evolution of mycophagy in Australia, as many of these species are consumed by mycophagous (i.e. fungus-eating) mammals. The role of mycophagous mammals in the diversification of Mesophelliaceae is generally assumed but requires further investigation. Additional sequencing of loci and exemplars is needed to elucidate the evolutionary history of Mesophelliaceae, as well as its fungal relatives and ecological partners.