Shortlisted for the 2024 Southwood Prize
Agostina Torres introduces us to her latest research which evaluated the dependence of community reassembly on inverse priority effects by experimentally removing the target invasives in field and mesocosm communities.
About the research
Overview
The study emerged as part of my PhD doctorate. Along with my supervisors, Drs. Martin Nuñez and Mariano Rodriguez-Cabal, we were trying to understand why secondary invasions occur after the removal of primary invasive species and whether there was anything we could do to improve the management of these communities.
In northern Patagonia, Argentina, the problem is alarming: invasive species are rapidly replacing native species, altering community structure, disturbance regimes, and the ecosystem services these forests provide. Even worse, any effort to remove these species seemed to lead to an even more problematic outcome—rather than a single dominant invasive species, the result was often communities invaded by multiple species, each with its characteristics, requirements, and limitations, making management and restoration even more challenging.
Strongly influenced by Prof. Tadashi Fukami’s work on historical contingencies in community assembly and Prof. Erika Zavaleta’s research on the impact of species losses from communties, we started considering how these stochastic processes might play a significant but largely overlooked role in invasive species removal aimed at ecological restoration. So, we set out to evaluate the effect of the order and timing of species removal during management.
With the invaluable help of our coauthor, Teresa Morán López, we decided to study this in communities invaded by multiple nonnative species following the removal of pine plantations on Isla Victoria (Parque Nacional Nahuel Huapi, Argentina), with two highly invasive shrubs being the dominant species: Rosa rubiginosa (Sweetbriar rose) and Cytisus scoparius (Scotch broom).
Since the climate in this region is highly seasonal, with dry summers and wet autumns and winters, we designed a contrast in removal timing: early removal took place in summer, during the peak growing season, while late removal occurred in autumn. For our experiment, we selected plots dominated by the two target species and removed their biomass in different removal orders (R. rubiginosa before C. scoparius vs. C. scoparius before R. rubiginosa) and removal timings (simultaneous early vs. late).
We found that simultaneous removals—the most common management practice—favored nonnatives, especially when done early. In contrast, sequential removals led to divergent outcomes: the removal of Rosa first promoted nonnative grasses at the expense of natives, while the reverse sequence had minimal impact. Overall, species with a more acquisitive strategy (i.e., high specific leaf area) tended to thrive.
Challenges
What surprised us the most was discovering that sequential removal of invasive species can actually reduce secondary invasions. Until then, simultaneous removal—getting rid of all nonnative species as quickly as possible—seemed like the most logical and efficient strategy. This finding challenged our initial assumptions and suggested that there might be an optimal sequence of removal that could make management efforts more effective in achieving restoration goals.
In developing countries, conducting science is full of financial and logistical challenges, and my research was no exception. Despite our efforts in seeking funding, our project was carried out without dedicated support and instead relied largely on our salaries. Most of the supplies and materials needed for our experiments came out of our own pockets. With only two field technicians at the institute supporting a staff of over 200, much of the fieldwork depended on the generosity of family, friends, and volunteers. These technicians work tirelessly, juggling multiple projects with minimal resources and constantly finding creative solutions to keep research moving forward despite the many constraints.
The lack of infrastructure also meant that we sometimes had to set up makeshift labs in our homes to process samples. I am deeply proud of Argentine science and of the valuable work we manage to accomplish with very limited resources. Our context has fostered a culture of resilience, creativity, and collaboration. However, far from romanticizing this reality, it’s important to recognize that chronic underfunding limits our ability to generate the knowledge needed to address urgent local and global challenges. Early-career scientists in Argentina must devote substantial time to navigating financial and logistical hurdles, limiting the time and headspace they can dedicate to research itself. Ensuring more funding opportunities would allow scientific progress to be driven by curiosity and impact, rather than constant resource constraints.
Next steps and broader implications
Our goal is to monitor community changes over the long term. We would like to maintain these plots permanently to assess whether the effects observed in the early stages persist, intensify, or diminish over time. Additionally, we are interested in exploring how these treatments interact with the introduction of native propagules and further investigating the underlying mechanisms driving the patterns we observed—particularly plant-soil feedback and indirect interactions involving non-native species, which can lead to widespread and unexpected effects.
Regarding the broader implications of inverse priority effects, we would like to expand our work to assess how widespread and significant historical contingencies are in shaping community responses to species loss driven by local extinctions caused by other anthropogenic global change drivers.
A key implication of our research is that small adjustments in management practices can lead to significant changes in community reassembly. Our study highlights the role of historical contingencies, showing that the order and timing of species removal can influence community recovery. Simply modifying when and in what sequence invasive species are removed—without relying on costly or technologically complex interventions—can affect community composition, the extent of secondary invasions, and the dominance of different functional groups.
We can leverage inverse priority effects to create more favorable conditions for native species recovery. In our study system, given that removing C. scoparius before R. rubiginosa mitigated negative effects on native species, we suggest that an optimal removal order could enhance restoration success—even more so than simultaneous removal.
About the author
Current position
I am currently a postdoctoral researcher in the Plant Ecology Group at IBZ, ETH Zurich. Here, I collaborate with Janneke Hille Ris Lambers’s group to study how forest communities reassemble in response to ongoing climate change. Our research focuses on whether these changes depend on the environmental context in which they occur and the traits of the species involved, and on how biotic interactions and historical contingencies shape the trajectories of community reassembly.
Getting involved in ecology
I was born in a city in the Argentine Pampas, a region almost entirely transformed into croplands and with very limited access to natural areas. This context sparked my interest in conservation and motivated me to pursue a degree in Environmental Sciences at Universidad de Buenos Aires. During my studies, I took courses in Ecology and met inspiring people doing fascinating research. I became captivated by the world of biotic interactions—how the presence (or absence) of a single species can influence an entire community, both in obvious ways and through more subtle, indirect effects.
My first research experiences explored this complexity through endophytic fungi that shape their grass hosts’ traits, affecting their interactions with herbivores and competitors. Ecology amazed me not only for its complexity but also for how deeply it intersects with our daily lives. Just as importantly, I developed a deep appreciation for the world behind the scenes—the community of passionate people working with dedication, joy, and mutual support to understand and protect our nature.
Current research focus
We have been exploring the theoretical aspects of inverse priority effects, aiming to frame them conceptually within community assembly theory. Based on a literature review and simulation models, we found that inverse priority effects are not limited to communities invaded by nonnative species, and we describe the mechanisms through which inverse priority effects can operate and the contexts in which they are expected to be most influential.
Beyond this, I am applying my expertise to understand the role of historical contingencies in other types of community reassemblies, such as those driven by climate change.
Advice for fellow ecologists
Choose to work with people who uplift you! For me, being surrounded by kind and supportive people has been invaluable for my professional growth. I believe that the best research emerges from environments that prioritize collaboration, generosity, and mutual care over sheer productivity. But honestly, I believe everyone has to find their path. What works best depends on individual circumstances and personal interests. I guess I just see context-dependency and historical contingencies everywhere!
Read the full article “Inverse priority effects: The order and timing of removal of invasive species influence community reassembly” in Journal of Applied Ecology.
Find the other early career researchers and their articles that have been shortlisted for the 2024 Southwood Prize here!
