Ms Josephine Potter-Craven1, Professor Jamie Kirkpatrick1, Dr Phillip Bell1
1University Of Tasmania, Sandy Bay, Australia
Introduced vespid wasps (Vespula germanica and V. vulgaris) are highly efficient predators of native invertebrates. They have the potential to reduce populations of threatened species and change ecosystem dynamics, yet their impact is largely
unknown in Australia. The introduction of vespid wasps has coincided with a decline in numbers of threatened Ptunarra brown butterflies (Oreixenica ptunarra) in Tasmania. The butterfly’s habitat has been fragmented by clearance for agriculture and forestry, and local extinctions of the species were previously thought to be due to its inability to fly long distances between habitat patches. We investigate the importance of the new threat of wasp predation in the decline of O. ptunarra in the highland grasslands of northwest Tasmania. Wasp control was trialled to determine whether it affected butterfly numbers. Current control methods decreased wasp numbers considerably, resulting in a small increase in butterfly numbers, indicating that wasp predation is keeping O. ptunarra at low densities. Without ongoing conservation measures, it is likely that butterfly numbers will stay low, potentially leading to genetic bottlenecks and more local extinctions. An increase in the intensity of wasp control, in combination with other conservation management methods, is required for the protection and recovery of O. ptunarra.
Josephine Potter-Craven is a PhD Candidate with the Discipline of Geography and Spatial Sciences at the University of Tasmania. She is studying conservation measures for the threatened Ptunarra brown butterfly in the highland grasslands of Tasmania and has recently published a paper regarding the impacts of predatory wasps on the butterflies, which she will speak about today.