Modelling tropical fire ant (Solenopsis geminata) dynamics and detection to inform an eradication project

Abstract

Invasive species threaten endangered species worldwide and substantial effort is focused on their control. Eradication projects require critical resource allocation decisions, as they affect both the likelihood of success and the overall cost. However, these complex decisions must often be made within data-poor environments. Here we develop a mathematical framework to assist in resource allocation for invasive species control projects and we apply it to the proposed eradication of the tropical fire ant (Solenopsis geminata) from the islands of Ashmore Reef in the Timor Sea. Our framework contains two models: a population model and a detection model. Our stochastic population model is used to predict ant abundance through time and allows us to estimate the probability of eradication. Using abundance predictions from the population model, we use the detection model to predict the probability of ant detection through time. These models inform key decisions throughout the project, which include deciding how many baiting events should take place, deciding whether to invest in detector dogs and setting surveillance effort to confirm eradication following control. We find that using a combination of insect growth regulator and toxins are required to achieve a high probability of eradication over 2 years, and we find that using two detector dogs may be more cost-effective than the use of lure deployment, provided that they are used across the life of the project. Our analysis lays a foundation for making decisions about control and detection throughout the project and provides specific advice about resource allocation.

Predicting the Global Distribution of Solenopsis geminata (Hymenoptera: Formicidae) under Climate Change Using the MaxEnt Model

“…ENMs have previously supported the development of strategies for invasive species and ecosystem management [ 47 , 48 ]. In addition, ecological modeling plays an important role in eradication programs of invasive species, particularly when limited resources are available [ 48 , 49 ]. However, there have been limited studies on S. geminata using modeling approaches.…”

Recent advances of quantitative modeling to support invasive species eradication on islands

“…and they are used 8 or more times (Baker et al 2017b). Importantly, this calculation was possible without having to train dogs and test them in-situ.…”

“…However, there are further layers of complexity to this, as species detection can guide removal efforts, making removal more effective (Baxter & Possingham 2011;Spring et al 2017). Similarly, spending more on species removal increases the confidence in eradication, meaning that surveillance effort can be reduced (Baker et al 2017b). Further, allocating resources between different actions goes beyond removal and detection, to include issues around preventing, quarantining, detecting and eradicating (Moore et al 2010;Rout et al 2011), early detection of species (Jarrad et al 2011) and detecting multiple species (Jarrad et al 2010).…”

“…Scientific papers -even when they are explicitly decisionfocussed -typically do not report on the decision itself and what role the modelling played. Speaking from our own experience, papers can be published before any decision was made (Baker et al 2018a), and policymakers do not always follow recommendations (Baker et al 2017b). In the latter case, there are often issues (which can be, but not limited to, political) that go beyond the scope of the modelling and that are challenging to discuss in a scientific publication.…”

The failure of success: cyclic recurrences of a globally invasive pest

“…This is largely due to the fact that alien species must negotiate a number of barriers to become established and invasive in new habitats (Hui and Richardson 2017), while recurrence only reflects population compensation after experiencing low population levels from environmental fluctuations and/or eradication (Manrakhan et al 2015, Lutscher and Musgrave 2017, Hausch et al 2018. Nonetheless, infested populations can serve as the propagule source to the invasion of other empty cells, while the sub-detectable population after successful eradication programs can also serve as propagule reservoirs for recurrent invasions (Bennett et al 2013, Baker et al 2017; both make EEP challenging and arbitrary (Liebhold and Tobin 2008, Ekesi et al 2016.…”