Invasive Species

Contributed Oral

Integrative Taxonomy and Invasive Species in Europe
Maria Vittoria Mazzamuto, Andrea Galimberti, Anna Loy, Adriano Martinoli

Knowledge on invasive species is important because it can help in the identification of major introduction pathways, thus reducing the risk of new releases, and can help in identifying factors responsible for their ability to establish, spread and become invasive, or to highlight evidence of stress that might limit this ability. In this research we used integrative taxonomy, a multi-disciplinary approach adding modern techniques to traditional morphology-based methods, to study 3 populations of invasive Callosciurus squirrels in Europe (Italy, Belgium and France). We combined molecular analysis (mtDNA markers), traditional morphometry (skulls) and geometric morphometrics (mandibles), to identify the introduced taxa, discover pathways of introduction and inform authorities to control and prevent future introductions. Genetic data revealed close similarity between French squirrels and Pallas’s squirrels, Callosciurus erythraeus, from Taiwan. Italian and Belgian squirrels formed an independent taxonomic lineage similar to known specimens assigned to Callosciurus erythraeus. These phylogenetic relationships have been confirmed by the shape and size of the mandible. However, morphometric analyses of the mandible also detected relevant differences in both size and shape between the closely related Belgian and Italian samples. According to the hypothesis of a common origin of the two populations, this finding may suggest a high phenotypic plasticity in C. erythraeus, and rapid phenotypic divergence rates likely related to different selective pressures in the invaded areas. This would also highlight the ability of a fast adaptation of C. erythraeus to a different environment, which is a key feature for the classification of a species as invasive. The identification of the species and the following field-based research have led to the classification of the Pallas’s squirrel as part of the list of Invasive Alien Species of European Union concern.

Consumption of Fire Ants, An Invasive Predator and Prey of Native Lizards, May Enhance Immune Functions Needed to Combat Envenomation
Catherine Tylan, Tracy Langkilde

Native ecosystems have been exposed to invasive species for decades, and the spread of non-native species is likely to continue into the future. Therefore, it is important to understand the effects invasive species have on the animals in ecosystems into which they have been introduced. We address this question using the eastern fence lizard (Sceloporus undulatus), which has been exposed to invasive stinging fire ants (Solenopsis invicta) for over 70 years. The presence of these invasive, predatory ants is associated with differences in native fence lizards, including to their immune functions, as compared to lizards from ecologically similar sites which are not yet invaded by fire ants. We sought to discover if these documented immune differences are directly stimulated by exposure to fire ant venom through stinging or consumption of ants by lizards that are naïve to fire ants. We measured a broad array of immune responses and found that being stung by fire ants increased some lizard immune responses and decreased others. In contrast, fire ant consumption increased lizard immune responses that were decreased when the lizards were stung; no responses were decreased as a result of fire ant consumption. These results may indicate that consumption of fire ants can bolster immune responses needed to combat later envenomation through stinging.

Quantifying the Impacts of Invasive Species on Imperiled U.S. Taxa
Aaron Haines, Matthias Leu, Emily Ritter, Lauren Bleyer, Lauren French, Delaney Costante, Laura Lielbriedis, Gokul Achayaeaj

Invasive species are one of the leading threats causing native species to require federal protection under the Endangered Species Act (ESA). Invasive species have been associated with the extinction of species listed under the ESA, while the control of invasive species has helped lead to species recovery. The goal of this project was to identify the top invasive species that threaten animals protected under the ESA, how invasive species negatively impact protected animals and how these impacts vary by taxa. We reviewed 615 federal register listing documents for all Threatened and Endangered (T&E) animal species from 1975 through 2020. We identified all T&E animal species impacted by invasive species, the taxa of these invasive species, and we summarized how invasive species negatively impact T&E animals through various interaction types (e.g., competition, predation, herbivory, disease, parasitism, adverse habitat modification etc.). We found that nearly half of T&E animals were negatively impacted by invasive species at their time of listing, and we identified 297 invasive species that negatively impacted T&E animals. The most invasive species included multiple species of Rattus, which impacted 104 T&E animal species, followed by pigs, goats, buffelgrass, fire ants and others. Many T&E animal species were influenced by more than one invasive species and had more than one negative interaction per invasive species. Invasive species mainly influenced T&E animals through predation, habitat modification and secondary competition. The proportion of T&E animals impacted by these interactions varied by taxa, with some taxa more susceptible than others.  For example, threats against T&E insects make up more than 50% of all negative interactions from invasive species. We hope our analysis can help raise awareness, provide opportunities to consolidate and improve data collection efforts, and improve coordination of invasive species control to benefit wildlife conservation.

Response of Forest Birds to the Invasive Fruit Pest Spotted Wing Drosophila
Daniel Roche, Scott Stoleson, Christopher Rota, William Oldland, Christopher Lituma

Spotted wing Drosophila (Drosophila suzukii) is a recently introduced invasive fruit fly that parasitizes fruits of many plant species in the United States. While its impacts in invaded forests are unknown, parasitism could reduce soft mast food for wildlife, including migratory songbirds. This may reduce food availability for birds in valuable early successional forest habitat before and during fall migration, when energetic demands are greatest. Our objective was to identify factors influencing frugivore and non-frugivore bird counts in regenerating timber harvests invaded by D. suzukii during the postbreeding season and migration. From July through September of 2019 and 2020 we mist-netted birds across 21 timber harvests at Allegheny National Forest in northwestern Pennsylvania. At each net we conducted fruit surveys, trapping for D. suzukii, and vegetation surveys to quantify factors influencing bird captures. We also collected a small sample of fruits at each mist net and observed for emergence of D. suzukii, for a measure of infestation rates of fruit. Total frugivore and eastern towhee (Pipilo erythrophthalmus) captures both decreased with increased numbers of D. suzukii trapped. Ovenbird (Seiurus aurocapilla) and hooded warbler (Setophaga citrina) captures increased and decreased with rates of Allegheny blackberry (Rubus allegheniensis) parasitism by D. suzukii, respectively. Non-frugivores and most focal species showed no strong responses to either D. suzukii variable. Large numbers of D. suzukii may be a nuisance to some frugivores, and parasitism may positively or negatively alter desirability of fruits for some, but not most bird species. D. suzukii may also influence arthropod communities, producing a trophic cascading effect on some bird species. Because D. suzukii is a recently introduced species, continued monitoring of its activity in forests and responses of wildlife communities will be critical to understanding whether patterns observed in this study continue or change long-term.

Food Resources and Territoriality of Wild Pig Sounders: Implications for Success of Control
John Kilgo, James Garabedian, Mark Vukovich, James Beasley, Peter Schlichting, Michael Byrne

Interest in control methods for invasive wild pigs (Sus scrofa) has increased with their rapidly expanding populations. Trapping is considered the most effective means of control in many situations. Traditional traps typically remove only a portion of each sounder but advances in remotely operated traps now facilitate capture of entire sounders (matrilineal social groups). If sounders are territorial, “whole-sounder trapping” renders whole territories free of pigs, but little research has explored the degree of territoriality among sounders. Our objectives were to assess the degree of territoriality in a wild pig population and whether the availability of a super-abundant resource, a municipal waste landfill, affected territoriality on the Savannah River Site, SC. We GPS-collared 1 mature sow from each of 18 neighboring sounders to monitor their space use in relation to each other. We estimated utilization distributions and quantified sounder territoriality using spatial overlap, volume of intersection (VI), and dynamic interaction metrics. Next, we modeled relationships between spatial overlap and VI and several covariates including distance to the landfill. Although neighboring sounders overlapped in space, average VI was uniformly low, never exceeding 0.10 for home ranges or 0.05 for core areas, indicating sounders rarely used areas that overlapped with neighbors. Additionally, sounders were rarely located together, with only 1% of pairs’ simultaneous locations being <50 m apart. Although VI was uniformly low, it increased for sounders closer to the landfill waste cells, indicating availability of landfill resources weakened the degree of territoriality among neighboring sounders. We conclude that although sounders behaved in a generally territorial manner, because home ranges overlapped in space, control operators working near rich, concentrated resources (e.g., landfills, crops) should not conclude they have removed all pigs from an area after the removal of a single sounder until additional monitoring reveals no others present.

Saving the World Two Evil Plant Species at a Time
Tiffany Sprague, Helen Rowe, Paul Staker, Barb Pringle

Non-native plant species alter wildlife habitat, displace native species, and contribute to catastrophic wildfires. Control of non-native plants can be difficult due to their prolific nature and is further complicated by limited resources, including time, money, and workforce. Previous studies investigating control techniques have been short term, included only a partial suite of removal techniques, or did not consider effects on the native plant community. Our objective was to determine cost-effective control measures for fountain grass (Pennisetum setaceum) and buffelgrass (Pennisetum ciliare) that best protect the native plant community over the long term. We established 25m2 plots in McDowell Sonoran Preserve in Scottsdale, Arizona, and tested combinations of cutting, herbicide, and hand pulling for both species. Over four years, we documented cost and effort for each treatment application and sampled the plant community in each plot. Fountain grass responded favorably to all treatments, whereas multiple herbicide applications per year were most effective for buffelgrass control. Pulling was the least expensive in small areas (<350m2 for fountain grass and <825 m2 for buffelgrass) and herbicide more cost-effective in large areas (depending on application frequency, cost per acre was $575–850 for fountain grass and $1425–1725 for buffelgrass). The native plant community responded favorably to removal of the non-natives and was not adversely affected by any of the treatments. Precipitation played an important role in native and non-native plant growth and limited the ability to apply herbicide in drought years. Regardless of treatment, a multiple-year effort was required to effectively control the non-native species. Results of this project will help land managers in arid regions choose appropriate treatments, based on the severity and distribution of infestations and available resources, to achieve long-term control of these non-native species.

Contributed Oral
Location: Virtual Date: November 3, 2021 Time: 4:00 pm - 5:00 pm