Faculty of Science, 2018
One research team with a $925,000 grant to study one of the world’s worst invasive species, and a second team exploring novel pest control solutions may help save New Zealand’s native wildlife and prevent millions of dollars in damage to primary industries. Both teams are led by Dr Phil Lester, an insect ecologist at Victoria University of Wellington.
Conservation in New Zealand has become inextricably linked with the act of eradicating invasive mammalian predators such as possums, rats, and mustelids (ferrets, stoats and weasels). Encouraged by the Predator Free 2050 movement, the act is arguably a vendetta against our mammalian classmates—vengeance for the indiscriminate murder and extinction of countless native bird species. Simultaneously, the act is a last-ditch effort to save what native birds remain—spearheaded by programmes such as the Department of Conservation’s Battle for our Birds.
The narrative is simple and fails to acknowledge the importance of invertebrates—the spineless organisms which make up over 95 percent of all known animal species. Vertebrates include all animals with spines or backbones—the groups of fish and tetrapods (amphibians, reptiles, birds, and mammals). Invertebrates include everything else—the likes of insects, spiders, snails, crabs, even corals. Not only are New Zealand’s native invertebrates faced with a multitude of threats to their continued existence but also introduced invertebrates are of both great benefit and great detriment to New Zealand.
Dr Phil Lester is an insect ecologist at Victoria University of Wellington. His work focuses on the ecology and population dynamics of social insects—invasive ants and wasps in particular.
A team led by Dr Lester has recently been awarded $925,000 in funding from the Royal Society of New Zealand’s Marsden Fund to study how pathogens and their hosts’ immune responses affect population and community dynamics, competitive ability and persistence in a model study system of Argentine ants.
Gene silencing and dsRNA technology will be used to stifle immunity against a number of known viral pathogens and bacteria. The effect of these treatments will first be studied in lab trials. A field experiment will then attempt to instigate a pathogen epidemic after applying treatments that result in maximum impact on immunity.
Dr Lester is also leading a project for New Zealand’s Biological Heritage National Science Challenge which will examine novel pest control technologies using invasive social wasps as a model study system. This project will explore promising ideas such as using pheromones to manipulate behaviour, using “Trojan horse” mites to deliver pathogens or toxins, using gene-drives to promote specific genes through populations, or using “Trojan female” techniques to limit the reproductive potential of populations.
The development of highly effective poison baits (such as Vespex) has greatly improved the ability to control invasive wasp species. However, alterations to the species’ underlying biology and ecology are seen as essential if the species is to be deleted from New Zealand altogether.
Hymenoptera is the taxonomic order of insects that includes ants, wasps and bees. Despite thousands of native species, a relatively small number of introduced species are of greatest significance to New Zealand.
The most beneficial of these introduced species is almost certainly the honey bee. Honey bees were deliberately introduced to New Zealand from 1839 and now form the foundation of a $5 billion apiculture industry. However, this industry is now threatened by other introduced invertebrates such as the disease-spreading parasitic Varroa mite and invasive wasp species. A 2016 colony loss survey found close to 12 percent of beekeepers attributed hive loss to invasive wasps.
Invasive wasp species have been estimated to cost the New Zealand economy more that $130 million a year. The biggest economic impacts are being reported by farmers, beekeepers, horticulturalists, and forestry workers. The abundance of invasive wasps also poses a significant threat to public health and recreation. Five species of social (hive-forming) wasps have been introduced to New Zealand since the 1940s: the German wasp, the common wasp, and three species of paper wasp. As the distribution and densities of these species have increased, so has their devastating impact on native species and ecosystems. Today, the biomass of introduced wasps far exceeds that of all our native bird species combined.
Argentine ants, ranked as one of the world’s worst invasive species by the World Conservation Union, have spread across much of New Zealand since first being discovered in 1990. The species poses a significant threat to New Zealand’s primary industries and to native species and ecosystems. It is for these reasons, along with the biological and ecological similarities with bees and wasps, that Dr Phil Lester and his team made the decision to use Argentine ants as a model study system.