Worldwide, the Sternorrhyncha (Hemiptera) are well known for their habit of excreting liquid honeydew. This resource mediates numerous interspecific interactions typically involving only insect participants. In Australia, lerp-forming psyllids convert this liquid excretion into a resource that solidifies on contact with air and can be shaped to make a protective shelter. Bell miner-associated dieback (BMAD) involves a uniquely Australian trophic cascade between eucalypts, psyllid lerp and birds. BMAD is a key threatening process and affects tens of thousands of hectares of forest, however, its incidence and severity is patchy making it difficult to fully understand.

The role of lerp-forming species of psyllid in BMAD is the subject of much uninformed speculation. Psyllid genera differ in host plant preferences, leaf age requirements, damage to host leaves and the attractiveness of their lerps to Bell Miners. Therefore, it is important to understand the composition of psyllid communities and how psyllid biology influences mechanisms behind BMAD trophic cascades. This study focused on the relative abundances of psyllid communities and host associations in BMAD and non-BMAD affected forests of NSW. Preliminary analysis showed no difference in psyllid diversity between BMAD and non-BMAD affected forest types, however, psyllid relative abundances were significantly higher at affected sites. Glycaspis lerps, which are high in sugar content, were the most abundant at BMAD affected forests. At non-BMAD affected sites psyllid genera had similar abundances. These findings are used to test the strength of the relationships between the availability of free carbohydrate and the incidence and severity of BMAD.

DNA metabarcoding is an emerging approach for monitoring biodiversity across a broad range of ecosystems. However, there are still uncertainties on whether DNA metabarcoding can detect community patterns as effectively as morphological approaches to species identification. In this study, we aim to investigate the performance of DNA metabarcoding in monitoring beetle biodiversity in managed forests, and further its usefulness for revealing ecological patterns. We used morphology-based and DNA metabarcoding (two gene markers: COI and 16S) approaches to investigate beetle species composition in 12 logging regrowth (~50 years old) sites and 12 old-growth counterparts in Tasmanian. We tested whether previous logging impacted beetle communities, comparing the utility of these two identification approaches. Our results showed that COI DNA metabarcoding yielded a similar number of operational taxonomic units (OTUs, 172) to the number of morphospecies (173), whereas the number of 16S OTUs (338) was inflated. We recovered distinct patterns of beetle species composition between regrowth and old-growth forests, using both COI DNA metabarcoding and morphology-based approaches. A similar but slightly lower percentage of variance related to logging treatment was explained with DNA metabarcoding compared to morphology-based identification. We conclude that DNA metabarcoding can be used for monitoring biodiversity and probing ecological patterns. Careful considerations are needed for choosing the gene marker as this determines several relevant aspects, such as the ability of curating OTUs and the availability of reference sequence databases. In addition, some loss of information compared to morphology-based identification suggests further improvement could increase the sensitivity of metabarcoding species detection.

Interactions among microbial symbionts have multiple roles in the maintenance of insect–microbe symbiosis. However, signals mediating microbial interactions have been scarcely studied. In the classical model system of bark beetles and fungal associates, fungi increase the fitness of insects. However, not all interactions are mutualistic, some of these fungal symbionts compete for sugars with beetle larvae. How this antagonistic effect is alleviated is unknown, and recent research suggests potential roles of bacterial symbionts. Red turpentine beetle (RTB), Dendroctonus valens LeConte, is an invasive pest in China, and it leads to wide spread, catastrophic mortality to Chinese pines. In the symbiotic system formed by RTB, fungi and bacteria, volatiles from predominant bacteria regulate the consumption sequence of carbon sources D-pinitol and D-glucose in the fungal symbiont Leptographium procerum, and appear to alleviate the antagonistic effect from the fungus against RTB larvae. However, active components of these volatiles are unknown. We detected 67 volatiles by Gas Chromatography-Mass Spectrometer (GC-MS). Seven of them were identified as candidate chemicals mediating bacteria-fungus interactions, among which ammonia made L. procerum consume its secondary carbon source D-pinitol instead of its preferred carbohydrate D-glucose. In conclusion, ammonia regulated the consumption sequence of these two carbon sources in the fungal symbiont.

Threatened freshwater swamps of the Mount Lofty Ranges provide habitat for over 120 plant species threatened at the national, state or regional level, including six EPBC-listed species. Over 90% of these threatened species are small understorey plants. Without disturbance, these species are outcompeted by dense shrubs, sedges and ferns. Ecological burns have been used successfully to regenerate some of the most threatened of these species.

An October burn of a swamp containing the only SA population of the orchid Thelymitra circumsepta increased numbers of flowering plants from 11 to 74, while an April burn of the largest surviving population of the EPBC-listed critically endangered orchid Prasophyllum murfetii flowering plants increased from 4 to 24. Critical to this recovery was fencing against overabundant kangaroos.

An October ecological burn undertaken on a private swamp on Fleurieu Peninsula, aimed at regenerating the EPBC-listed critically endangered Hibbertia tenuis also increased plants in the burnt area from ten to ̴ 400. The decision to burn was based on PhD research at Adelaide University which found the species to be stimulated by smoke and to germinate best in spring and autumn temperatures and day length.

Timing of burn is critical to success. This is illustrated by PhD research at Flinders University which found declines in the EPBC-listed Eriocaulon carsonii where its mound spring habitat was burnt in winter. This increased water competition by reeds which regenerated strongly due to their winter dormancy.