When I started my PhD, I had no idea where it would take me. I was interested in sustainable agriculture and agro‐ecology, so the idea of working on biological control of weeds by weed seed predators was very exciting but also completely new to me. My advisor Paula Westerman and I thought about exploring how field edge vegetation influenced weed seed predator's populations and seed predation rates, but it turned out that our most important seed predators were actually not using the field edge at all. Instead, they were right in the middle of fields, visible and active all spring and summer long. In semi‐arid cereal systems in northeastern Spain, harvester ants from the species Messor barbarus were everywhere, at least whenever field management allowed them to be (flood‐irrigated fields had no ant nests, understandably enough).
I started measuring weed seed predation by ants in tilled and no‐till fields, and in rain‐fed and irrigated systems, and at the same time, I was trying to understand more about how these social insects behaved and why. It was fascinating to me, and I remember spending hours looking at all these ants going in and out of a nest, as if they knew exactly what to do and where to go (and they actually did!). Besides measuring predation rates, timing and seed preferences, I spent a lot of time counting ant nests in many cereal fields. We had to be in the field by sunrise, because as temperatures rose above 30°C (which usually happened at 10:00), ants would retrieve to their nest and close the door, making it very hard to determine whether the nest was actually alive. While counting nests, I observed how colonies would interact with each other and how these encounters sometimes resulted in fierce wars and the death of some nests.
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