Posted by Delayn Fritz @WildOptic

My previous blog post focused on global trade and the invasion process as a whole, but what happens to an exotic species after it becomes established? Post-establishment spread and dispersal is the next step for an exotic species transforming into an invasive species. Of particular interest are the causes of that spread, both natural and non-natural.

The simplest way that a species spreads is through its competitive edge. A study of the competitive nature of the Argentine ant (Linepithema humile) showed that they completely overcame native ants in North America in terms of resource gathering. Being able to displace native species allows the exotic invading species to take over their turf and spread locally. In fact displacing or removing native species may even lead to an ecological meltdown which can cause other invasive species to establish and cause a positive feedback loop.

An Argentine ant (Linepithema humile) specimen. Photo Credit: April Nobile / © AntWeb.org / CC BY-SA 3.0

Another way for an exotic species to spread is environmental shift. This can be through habitat fragmentation and disturbance wherein a gap in the normal functioning of an environment displaces the native competitors to a point where the exotic species become dominant. One form of this that has been documented repeatedly is the increased proportion of exotic plants along roadsides, which act as a corridor for exotic species. Climate change may play another role in spread, as one study showed that increased rainfall had a positive effect on range expansion while drier years actually decreased the range of both Argentine ants and native ants in North America.

Long range jump dispersal patterns are also a key factor in spread, but this is often achieved by non-natural means. This jump dispersal usually occurs by the exotic species hitching a ride on internal trade routes or just regular vehicles. This leads to species achieving spread rates a whole order of magnitude  higher than the distance travelled by normal dispersal. It has also been shown that when this jump dispersal occurs it can actually increase the spread rate by up to three orders of magnitude.

For my MSc, I will be trying to analyse some of the data on currently established exotic ant species in New Zealand, and using taxonomic collections and their historic data to try and figure out the spread rates of different species and see if this is related to any of the aforementioned spread processes.

 

Delayn Fritz is an MSc student in the Centre of Biodiversity  and Biosecurity, School of Biological Sciences, University of Auckland. He is interested in the invasion process of ants (Hymenoptera: Formicidae) in New Zealand. He is supervised by Darren Ward and Eckehard Brockerhoff (Scion, B3).

Post by Anna Frances Probert @AFProbert

Human movement and global trade are ever-increasing. Last year 5.6 million people arrived into New Zealand and more than 1.7 million containers moved through New Zealand ports. This increases the risk of unwanted organisms (disease and pest species) arriving and establishing. The management of these risks (both pre border and post border) is what biosecurity encompasses.

Unwanted organisms can have dramatic impacts on our livelihoods – impacting economic, social and environmental values. In most circumstances, introduced species (that is, species that are not native to New Zealand) are benign. Many of them won’t survive to establish, having evolved to thrive in different environments. However, a small subset do survive, establish and then spread across the landscape, becoming ‘invasive species’. If we perceive these to have a negative impact, then they are considered ‘pest species’.

Preventing new organisms from entering New Zealand is much easier and more cost-effective than trying to eradicate or control them once they slip past the border. Although there have been several successful eradication programmes conducted in New Zealand – for instance the Argentine ant on Tiritiri Matangi and the Queensland fruit fly in Auckland.

Recently, government funding for the Predator Free New Zealand project was announced, which aims to support the large-scale eradication of rats, possums and mustelids from New Zealand. This ambitious project will have massive benefits for native flora and fauna as well as remove the costs associated with the long term management of these pests.

The announcement of this project coincided with the launch of the government’s Biosecurity 2025 strategy, which aims to review and future-proof New Zealand’s biosecurity system. The current Biosecurity 2025 document outlines proposals for what might be in the direction statement, which will guide New Zealand’s biosecurity system into the future. As a nominated ‘Biosecurity Champion’, myself along with Rudd Kleinpaste, Bruce Wills and Graeme Marshall are involved in promoting the importance of biosecurity and public involvement in the consultation process.

Public submissions are now open, and as part of the consultation process public meetings and hui are to be held around the country.

Biosecurity is an issue that affects every New Zealander. I encourage everyone to make a submission, so that we can work together to protect our country from unwanted organisms, now and into the future.

Anna Probert is a PhD student in the Centre for Biodiversity & Biosecurity, School of Biological Sciences, University of Auckland. She is using ants as a model to assess the risk posed by exotic invertebrates to native ecosystems. She is supervised by Margaret Stanley, Jacqueline Beggs, and Darren Ward.

Posted by Cate Macinnis-Ng @LoraxCate

Ever wondered how much water a kauri tree uses? Find out in my video for the 180 Seconds of Science competition. A vote for my entry will help me win funds towards my research.

#180science is a joint competition run by the Australian Academy of Science EMCR Forum and the Royal Society of New Zealand Early Career Researcher Forum. These organisations represent emerging researchers in their respective countries. Voting closes on 22nd August at the conclusion of National Science Week in Australia so get in quick!

 

Dr Cate Macinnis-Ng is a Senior Lecturer and Rutherford Discovery Fellow, School of Biological Sciences, University of Auckland.  She is a plant ecophysiologist and ecohydrologist working on plant-climate interactions.