Coextinction of Pseudococcus markharveyi (Hemiptera: Pseudococcidae): a case study in the modern insect extinction crisis

Abstract

The majority of modern insect extinctions are likely unrecorded, despite increasing concern for this hyperdiverse group. This is because they are either yet to be discovered and described, their distributions and host associations are poorly known, or data are too sparse to detect declines in populations. Here, I outline the likely extinction of an Australian mealybug, Pseudococcus markharveyi Gullan 2013, which was discovered and described less than 15 years ago but was highlighted recently as one of five most threatened invertebrates in Australia from recent bushfires. The synergistic threats of dieback disease (Phytophthora cinnamomi Rands, 1922) and inappropriate fire regime as a consequence of climate change, have decimated host plant populations of the critically endangered Banksia montana (George, 1996) (Mast & Thiele 2007) and the montane habitat of both organisms, thereby leading to the coextinction of the mealybug. Its loss occurred despite attempts at conservation management and illustrates the general insect extinction crisis that Australia, and the world, is facing. The majority of Australian mealybugs are not receiving the same attention as P. markharveyi. Many poorly known species either remain undetected, without formal names, or data on their distribution, abundance and critical habitat are too scant to assess their conservation status. I also discuss the diversity of Australian mealybugs more generally and their need for conservation.

Population declines and the conservation of insects and other terrestrial invertebrates in Australia

“…2021; Hogendoorn et al . 2021; Moir 2021) report severe declines at the site and landscape scale within the last decade.…”

“…2021; Hogendoorn et al . 2021; Moir 2021), together with a very recently published 8 year study of the diet of the Australian hobby Falco longipennis during the Millennium Drought (Debus et al . 2020), have identified rapid declines in insect abundance in the immediate past at small spatial scales (site and landscape) (Fig.…”

“…2021; Hogendoorn et al . 2021; Moir 2021) deal with case studies of individual species that provide evidence of recent decline and extinction. The Bogong Moth Agrotis infusa is perhaps one of Australia's most iconic insects and famous for its remarkable long‐distance migration and aestivation in the Australian Alps, as well for its cultural significance among Indigenous Australians.…”

“…The likely extinction of the Banksia Montane Mealybug Pseudococcus markharveyi (Fig. 2) in the Stirling Ranges, WA (Moir 2021), may well be the very first documented casualty from these mega‐fire events. Pseudococcus markharveyi is a short‐range endemic and host specialist of the critically endangered tree Banksia montana (Gullan et al .…”

Design considerations for rapid biodiversity reconnaissance surveys and long‐term monitoring to assess the impact of wildfire

“…Surveys detected individuals at the only accessible location in the river catchment, confirming species persistence. In contrast, a post‐fire reconnaissance survey found that the only known population of the Banksia montana mealybug Pseudococcus markharveyi was extinguished in the 2019–2020 fires, and consequently, the species is now considered likely to be extinct (Moir, 2021).…”