Abstract
Strategies to control ongoing biological invasions are often developed by modelling the invasive species' population and aiming to reduce its abundance. However, if the ultimate objective is to protect and restore native species, focussing solely on the invader may not be optimal because it does not account for (i) species interactions that can cause the invader's impacts to depend nonlinearly on its abundance, (ii) collateral damages to native species incurred due to nonspecific removal methods or (iii) native-invader trait differences. To identify an invader suppression strategy that maximizes average native population size, we applied optimal control theory to a two-species model of a native species threatened by an invasive competitor. We examined trade-offs between iterative physical removals that selectively target invaders and intensifiable chemical control that is nonselective but has higher efficacy. We found that while iterative removals were capable of supporting large native populations when applied continuously, cost could be prohibitively high. In contrast, when favourable native-invader trait differences enabled native species to re-establish more quickly than invaders, intensifiable methods could achieve substantial restoration benefits at lower cost by focussing removal effort into periodic, high-efficacy events. In a metapopulation, removals that rotated among spatial patches were optimal when the native species had higher dispersal, whereas synchronous removals were preferred when native recovery was initiated locally and the invader could disperse. For a case study in Hawaiian streams, we compared how effective two alternative methods of removing invasive live-bearing fishes (poeciliids) might be at restoring the endemic freshwater goby Sicyopterus stimpsoni. We found that rotenone (a piscicidal chemical) offered superior benefits when the control budget was small and efficacy was high, but that electrofishing (use of electricity to manually collect target fish) was better with larger budgets and in many lower-efficacy scenarios. Synthesis and applications. Our findings demonstrate that, by accounting for species interactions and collateral damage, invasive species control strategies can be optimized in light of species traits. Choices about the timing, locations and types of removal events present opportunities to increase the efficiency with which invasive species suppression benefits native species.
| Original language | English |
|---|---|
| Pages (from-to) | 2636-2651 |
| Number of pages | 16 |
| Journal | Journal of Applied Ecology |
| Volume | 60 |
| Issue number | 12 |
| DOIs | |
| State | Published - Dec 2023 |
Funding
This manuscript has been authored in part by UT‐Battelle, LLC, under contract DE‐AC05‐00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid‐up, irrevocable, worldwide licence to publish or reproduce the published form of this manuscript or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe‐public‐access‐plan ). Handling Editor: We sincerely thank Mike Blum, Derek Hogan, Galen Holt, Pete Lisi and members of their Hawaiian stream conservation team for discussion of amphidromous goby restoration efforts that inspired this study and for hosting a field visit by Timothy Lambert. We thank the editors, three anonymous reviewers, and the LimnoLab and Ellner groups at Cornell University including Thomas Detmer, Kimberly Fitzpatrick and Anna Poulton for their help in improving the manuscript. We would like to recognize support made available through the US Department of Defense Strategic Environmental Research Development Program (SERDP) that funded project RC-2447; a Cornell University Presidential Life Science Fellowship; and a National Science Foundation Graduate Research Fellowship under Grant No. DGE-1650441. Computation was performed on Cornell's BioHPC Cloud with support from the Cornell Atkinson Center's Sustainable Biodiversity Fund and a Kieckhefer Adirondack Fellowship. We sincerely thank Mike Blum, Derek Hogan, Galen Holt, Pete Lisi and members of their Hawaiian stream conservation team for discussion of amphidromous goby restoration efforts that inspired this study and for hosting a field visit by Timothy Lambert. We thank the editors, three anonymous reviewers, and the LimnoLab and Ellner groups at Cornell University including Thomas Detmer, Kimberly Fitzpatrick and Anna Poulton for their help in improving the manuscript. We would like to recognize support made available through the US Department of Defense Strategic Environmental Research Development Program (SERDP) that funded project RC‐2447; a Cornell University Presidential Life Science Fellowship; and a National Science Foundation Graduate Research Fellowship under Grant No. DGE‐1650441. Computation was performed on Cornell's BioHPC Cloud with support from the Cornell Atkinson Center's Sustainable Biodiversity Fund and a Kieckhefer Adirondack Fellowship.
Keywords
- dispersal
- invasive species
- optimal control
- removal specificity
- resistant life stage
- species traits
- suppression