Developing management strategies to combat increased coextinction rates of plant dwelling insects through global climate change
Adaptation Research Grants Program
Executive summary from final report:
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. Their extinction is termed ‘coextinction’ as it occurs either through the loss of the host or some change in the population of the host.
Attempting to foresee the impacts of climate change without considering species interactions, exemplified by dependent-host relationships, results in a failure to generate comprehensive predictions or unambiguous suggestions for amelioration. Whilst innovative frameworks are available to assess the potential threat presented by climate change, these are often applicable only when background information is available for the target taxa. In Australia, the vast majority of plant-dwelling insect species do not even have names as yet. Given the numbers of species involved and the lack of knowledge on the majority of plant-dwelling insects, their management can be overwhelming.
This study was commissioned to investigate the threat posed by climate change to plant-dwelling insects, and provide adaptation management options for their conservation. This was achieved in a multifaceted approach. Firstly, we monitored the climate across a series of altitudinal transects with a series of weather data loggers. Secondly, we analysed the host-breadth of insect species from a large database featuring 104 different host plant species. Thirdly, experimental translocations of three co-threatened insect species with their host plants were trialled for the first time in Western Australia. Finally, end-users from industry, non-government organisations, State and Federal government were surveyed to identify barriers in insect conservation and help develop management outcomes that would be most applicable to organisations.
Insect groups that appear most prone to extinction are sessile feeders and highly host specific groups e.g. whiteflies, scales, mealybugs (Hemiptera: Aleyrodidae, Coccidae, Pseudococcidae). Weevils (Coleoptera: Curculionidae), particularly smaller species from the genera Apion and Cydmaea, were also host specific and at high risk but these could be dominated by dispersal-limited species such as brachypterous species. Surprisingly, mobile plant louse groups (Hemiptera: Psyllidae and Triozidae) were also at high risk. Internal plant-feeding insects (called endophages) such as gallers and leaf miners are also predicted to be at high risk. Regions such as gullies and mountains provide refugia for some species. The fluctuations in temperature (less within refugia), and humidity (higher in refugia) appear particularly important in these habitats.
With the assistance of end-users, an adaptation management framework was developed to assist with the conservation of plant-dwelling insect species, after they are identified as in need of conservation action. Initially developed to manage climate change, this framework is flexible and can be used when the insect requires conservation action to ameliorate the impacts of other threatening processes. Plant-dwelling insect conservation methods are in their infancy as land managers are struggling to determine which insect species currently reside within their lands, let alone which are in need of conservation action. This is due to a lack of expertise and resources. These issues were found to be the most important factors inhibiting end-users from considering plant-dwelling insects in their management plans. To assist land managers with these concerns, we suggest the employment of dedicated conservation entomologists who would be charged with bridging the interface between taxonomists, government conservation bodies, land managers and disturbance ecologists. Their primary job would be to identify those insects most at risk of extinction, nominate them for listing, and develop management plans to ensure their survival.
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