2025 HARPER PRIZE SHORTLIST: For the next two weeks, we are featuring the articles shortlisted for the 2025 Harper Prize. The Harper Prize is an annual award for the best early career research paper published in Journal of Ecology. Amanda Vieria da Silva’s ‘Ants on flowers: Protective ants impose a low but variable cost to pollination, moderated by location of extrafloral nectaries and type of flower visitor‘ is one of those shortlisted for the award.
About the paper:
What is your shortlisted paper about, and what are you seeking to answer with your research?
Despite the benefits of being involved in mutualisms, organisms also pay costs. When organisms engage in multiple mutualisms simultaneously, additional costs may arise that would not occur when engaging in a single mutualism alone. For example, the presence of one mutualistic partner can have a negative effect on another mutualistic partner. Consequently, the focal organism may have its fitness reduced when both partners are present. This is known as the ecological cost of mutualisms. My research aims to explore how the ecological costs of mutualisms affect the focal organism and whether this effect is modulated by traits of the focal organism. For that, I conducted a meta-analysis evaluating the effect of protective ants on pollination.
Were you surprised by anything when working on it? Did you have any challenges to overcome?
Conducting a meta-analysis is never an easy task! I came across more than 500 papers to read. Surprisingly (or perhaps not), most of them were not actually about mutualisms. Among those that were, some of them I had no idea how to extract the data. I’m so grateful to be part of a team that supported me during the entire process. Another important aspect of meta-analyses is that we depend on the data reported in primary studies. Consequently, we could not answer all the questions we had because we did not have data for that. Regarding the results, we were really surprised to find that protective ants have a negative effect only on flower visitation, especially by bees, and that this negative effect did not translate into a reduction of plant fitness.
What is the next step in this field going to be?
Our research shows that the outcome of mutualistic interactions is complex and depends on the joint effect of mutualistic partners. Although we explored only plant traits, we expect that traits of ants and pollinators also affect the outcome of mutualisms. We could also add another layer of complexity by incorporating environmental variables. For instance, if plants invest more in biotic defence in environments where leaves are more costly to produce, are the ecological costs of mutualisms stronger in these environments? Finally, if ecological costs are an important selective force, what are the evolutionary consequences of the ecological costs of mutualisms?
What are the broader impacts or implications of your research for policy or practice?
Our research highlights that plant pollinated exclusively by bees are more prone to be negatively impacted by ants. This may have consequences for crops that rely on bee pollination, such as blueberries, cranberries, tomatoes, potatoes and others.
Amanda dissecting a Chamaecrista (Fabaceae) flower to measure some traits that could possibly prevent ant access to flowers at Kew Royal Botanical Garden (left). A small flower of Chamaecrista dissected by Amanda (right).
About the author:
How did you get involved in ecology?
I have always loved nature and growing up in a small city with many green areas certainly helped! I always knew I wanted to become a biologist; however, I initially thought I would study animal genetics. Somehow, I came across ecology when I was an undergrad student. There was an opportunity to study ecology of snakes. Although I discovered I’m not brave enough to work with snakes, that opportunity made me realise that I’m passionate about ecology. I have always enjoyed understanding how organisms interact and what modulates these interactions. Since then, I study ecological interactions, especially the cost of these interactions.
What is your current position?
I’m currently a research assistant at the Plant-Animal Interactions Laboratory at the Federal University of ABC, in Brazil, coordinated by Dr. Anselmo Nogueira. As a research assistant, I help graduate students to develop their research, especially by providing statistical and writing support. At the same time, I have the freedom to pursue my own research interests.
Have you continued the research your paper is about?
Yes, during my PhD I also investigated the evolutionary consequences of ecological costs of protective ants on plant trait evolution. We found that the emergence of extrafloral nectaries, which attract protective ants, shows a negative evolutionary correlation with poricidal anther, a floral trait associated with exclusive bee-pollination. However, a few plant genera still interact with protective ants and are exclusively pollinated by bees. How is this possible? We hypothesised that these plants might have traits preventing ant access to flowers. Then, I measured a lot of floral traits in Chamaecrista (Fabaceae) to evaluate this hypothesis. Regarding the future, I’m working with Dr. Anselmo Nogueira on a grant proposal for a follow-up project as a postdoc.
What one piece of advice would you give to someone in your field?
I could never have accomplished all the things I did without the support of people around me. At some moments, I felt completely incapable of dealing with the stress of being a scientist and I even told my advisor that I wanted to quit my PhD. She said “keep things at your own pace and enjoy your PhD. The only difference between you and me is time. You will get there, you just need to be patient with yourself”. Whenever I feel that I cannot handle a situation, I remember her advice. So, if I had to give a piece of advice, I would say: choose your research team carefully! Choose people who cares not only about research but also about each other. This makes the difference!
