Approximately a quarter of global terrestrial biodiversity is represented by plant dwelling insects and the potential for thousands of species to be extinguished through widespread disturbances such as a changing climate is high. From a large database of 1,019 insect species on 104 plant species, we identified that 70 species were of immediate conservation concern due to their reliance on threatened plant species. A further 15 insect species were of lesser conservation concern because they rely on several threatened plant species for survival. Of those insects that feed from non-threatened plant species, 178 host-specific species are likely to be at risk in the event that climate change or synergistic factors reduces their host plant’s range size. Insect groups that appear most prone to extinction are sessile feeders and highly host specific groups such as whiteflies, scales, mealybugs. Many weevils are also host specific and at higher risk, possibly as they are dispersal inhibited, such as through brachyptery. More surprisingly, mobile plant louse groups (Psylloidea) were also at high risk. Endophagous insects are predicted to be at high risk, but were under-studied here.
Regions such as gullies and mountains provide refugia for some species. The fluctuations in temperature (less within refugia), and average humidity (higher in refugia) appear particularly important in these habitats. Particular vegetation types are associated with refugial regions, with a recognised Threatened Ecological Community (TEC) of flora species associated with the highest peaks of the Eastern Mastif, and there is evidence of insect species restricted to these peaks. For the majority of plant species that are not restricted to certain areas, their insect assemblages differ significantly between plant populations, particularly across different mountains.
With the assistance of end-users, we have developed an adaptation management framework. The framework assists with conserving plant-dwelling insect species, after they are identified as in need of conservation action. Whilst the primary reason for the development of the framework was to provide adaptation actions in the face of climate change, the framework can be used when insects require conservation action to ameliorate impacts of other threatening processes. Previously published frameworks can be utilized to determine whether an insect is threatened with extinction. Despite the availability of such tools, a survey of end-users still indicted that lack of expertise is the most important factor inhibiting considering plant-dwelling insects.
Land managers currently struggle to determine which insect species inhabit their lands, let alone knowing which are in need of conservation. To assist land managers with these problems, we suggest the employment of dedicated conservation entomologists by the Federal and State governments. Their role would be to bridge the interface between taxonomists, government conservation bodies, land managers and disturbance ecologists. The conservation entomologist’s principle tasks would be to identify insects most at risk of extinction, nominate them for listing, and develop management plans to ensure their survival.