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Ants in the Coffee Farm, the Urban Garden, and in the Fight for Justice (Stacy Philpott)
Ant-Plant Interactions in Citrus and Peach Orchards (Kate Mathis)
Restoring Communities with Edible Forests (Naim Edwards)
Ants: Biodiversity and Ecological Services in Colombian Agroecosystems in Times of Environmental Crisis
Inge Ambrecht
Ants in the Coffee Farm, the Urban Garden, and in the Fight for Justice
Stacy Philpott
This is an ant. This is an ant colony. All of the worker ants are female, ants are haplo-diploid, some ants have soldiers, and the queen is in charge. Worker ants use many different foraging strategies – mass recruitment, tandem running, and various forms of chemical communication necessary for finding and collecting resources to feed the larvae back in the nest. Ants nest in a variety of locations from arboreal carton nests, to fungal caverns, to massive underground tunnels, in ant-plants, and of course, in hollow twigs. Among the resources that ants collect are insect prey. Ants are important predators, feeding on a of prey items, including herbivores in agricultural systems.
Those simple (maybe obvious facts to this crowd) are things that I learned in my second semester as a PhD student in an independent study with Ivette (in that famous office where I first met her). She suggested that I read the book “THE ANTS”. I made it through most of the book, and those basic aspects of ant natural history that we discussed have shaped my research and my students’ research for the past 25 years. I learned a lot more about ants and ecology from Ivette during our early years at Finca Irlanda. And while in Michigan got generally inspired to work in both coffee agroforests and urban gardens. And in both systems, I ask questions about how agroecosystem management and landscape changes affect ants (and other insects), insect conservation, insect interactions, and their roles in providing ecosystem services. Today, I want to highlight four areas my work (and my students’ work) that is inspired by Ivette: (1) ant foraging ecology, (2) ant nesting ecology, (3) ant predatory effects, and (4) ants in the pursuit of justice.
Ants use many different foraging strategies, but for arboreal ants, they tend to not want to go on the ground to move around. So, farmers have used bridges between trees for centuries to encourage ant movement from plant to plant. Depicted here are bamboo bridges used by ancient Chinese farmers to move ants between citrus trees to provide biological control services. In discussing this ant management strategy, Ivette said to me, “Why don’t you try putting up strings to see if ants will use them?”. So I did. I put up strings in coffee farms that connected shade trees with ant nests to coffee plants, put some tuna on the coffee plants, and monitored over a week and a month to see if the ants would use them. And they did. Ants used at least 40% and up to 100% of the strings (depending on the species and timeframe), and they picked up tuna to carry across the tightrope back to the nest. And then like ants communicating on a foraging trail – the word spread that strings work. So many years later, Estelí Jimenez-Soto and Jonno Morris set up an experiment to test how adding strings would influence ant abundance on coffee plants and removal of the coffee berry borer. We found that plants connected with string have more ants, and that more borers are removed from plants connected with strings. This paper won the Peter Ashton Prize for the outstanding article published in Biotropica by a student. Hearing about Esteli’s project motivated my PhD student Azucena Lucatero (who got her start in the colony with Theresa Ong) to try this in urban agroecosystems in California – Would an array of strings in vegetatively simple and complex garden plots influence natural enemies or prey removal? Well, the answer is no, not really – the strings didn’t have a big effect. But Azucena did learn that vegetation complexity and connectivity within the plots had a significant positive effect on natural enemy richness and abundance. Sanya Cowal (a colony member hailing from Heidi Liere’s lab) heard about the idea of the strings, and the function of the natural vegetation connections. She compared ant activity and coffee berry borer removal from coffee plants on plants without connections to those connected with string, and plants connected with real vegetation bridges like branches and vines. She found that strings work, but vegetation connections are even better, with more borers removed from coffee plants with vegetation connections to the trees. This data was preliminary data for a successful NSF graduate fellowship award. And that ties up the part on strings.
Next, we turn to the ant nesting ecology. Ivette suggested, “why don’t you put up some bamboo twigs to study things about ant nests?” Well, I certainly took her up on that one – and have basically made a career out of studying ants colonizing nests. This has allowed me and my students to answer questions related to resource availability, and how nesting resources can alter ant diversity, composition and community assembly processes. In a first study, I learned (with Paul Foster) that twig-nesting ants occupy similar percentages of hollow coffee twigs in different habitat types, but many more artificial nests in low-shade coffee, indicating that arboreal ants are nest-site limited in more intensively managed coffee farms. I then explored the effects of Azteca on colonization by twig-nesting ants finding that both on coffee plants, and on shade trees that competitive, aggressive interactions with Azteca can limit colonization by twig-nesting ants and also alter community composition. And these projects about nests also spread through the colony – Kate Ennis explored how presence of Pheidole synantropica (a ground nesting ant) would alter nest colonization on coffee plants. We found that when Pheidole abundance was high, they prevented nest colonization on coffee plants; but when abundance was low, they didn’t have an effect on colonization. Again, ant aggression influences arrival and survival of other ants. And with Estelí, we documented that a diversity of nests – specifically nests with an array of door sizes — can promote a higher number of ant species in both coffee plants and on shade trees. This nest work also inspired some students (like George Livingston) to delve deeply into metacommunity theory and community assembly processes – In these papers, we used data from artificial nests, coffee twig nests, and shade tree nests. The upshot? Twig-nesting ants can be classified into different groups based on their local and regional abundance, and only one species – the super abundant Pseudomyremx simplex seems to drive co-occurrence patterns for other ants, while the others follow random assembly processes. And I can’t possibly leave out the one artificial nest experiment done in urban gardens by my master’s student Russ Friedrich. Russ introduced a diversity of artificial nests – everything from ping pong balls to bamboo garden stakes. He found that ants occupied both wood and man-made materials, but large tube-shaped nests were the most popular with ants, across three urban habitats examined, especially when put in bags with other nest materials. So, in the end, I did really find a comfortable home studying these ant nests.
The third item that Ivette gave me a lot of advice on was doing predation experiments. She suggested putting tuna all over the place to see what would happen, and I complied, and then quickly graduated to more realistic ant prey. The first of my predation studies showed simple behavioral differences in the ways that ant species recruit to baits (how fast and how many), and the ways that they respond to prey items (either taking them away or throwing them onto the ground) but overall, prey were removed much more often from plants with ants. Other colony members, led by Dave Gonthier, documented that several different ant species are all effective in lowering damage by a real coffee pest – the coffee berry borer. Regardless of the number of ant species (or ant diversity), some experiments, lead by Ashley Larsen, showed that plant protection by ants from the borer is only significant in the shadiest coffee farms, and not in more intensively-managed systems- meaning that ant impacts likely diminish with coffee intensification. Moreover, Aldo de la Mora found that that ant abundance and ant richness are strong positive predictors of prey removal from coffee farms on multiple vegetation strata – and more consistent predictors than other local and landscape management factors. We also did some fun lab experiments where we looked at how many fruits were infected with borers under different diversity treatments. All species and combinations were good, and about the same compared to the controls – so it seemed like diversity wasn’t super important, until we added parasitic phorid flies to the cages. These phorids attack Azteca ants, and reduced the ability of this species to protect the plants, giving the second and third species treatments the ability to shine… and again showing that ant diversity does matter for function, in sometimes surprising and cryptic ways. I’ve also continued ant predation studies in the urban gardens – just last summer testing prey removal by ants in different garden microhabitats. I found that ants are the most abundant and effective predators of small insect prey like pest eggs, and that even the invasive Argentine Ant provides important ecosystem services.
So let’s move on to the fourth area: ants in the pursuit of justice. I don’t know if it is the colony, the cooperation, or the camaraderie – but working with ants (and with Ivette) also inspires and great deal of collaboration and desire to work towards social justice. And anyone who has ever seen a Finca Irlanda Azteca ant map knows that all of the ants are revolutionaries. Ivette always encourages us to think about not just think about the science, but also to ask questions about how coffee or garden management may affect grower livelihoods. She inspires us to think about educational justice – be it in the Atlantic coast of Nicaragua, or in our own international research exchange programs – like this collaboration between ECOSUR and UC Santa Cruz. Members of our extended ant supercolony will always show up to defend justice for science and to march at the protest. And of course, we are always gathering and reuniting time and again to plan the next revolution together. I have always appreciated Ivette’s insight and for treating me from the start like a valued colleague and equal like the worker ants do. As this Tierras Milperas gardener from California said, “vamos caminando como hormiguitas – ni uno mas alto que el otro”. With that point of view, we can achieve a lot!
Gracias, Ivette!!!
Ant-Plant Interactions in Citrus and Peach Orchards
Kate Mathis
The Derivation of Functional Responses from Individual Feeding Processes: Implicit Assumptions, Prospects and Limitations
David Alonso
Restoring Communities with Edible Forests
Naim Edwards
Edible forests are landscapes that incorporate perennial, woody fruit and nut plants. These plants can compliment and add to the fabric of urban agriculture and small scale polyculture by increasing plant diversity and crops that require less soil disturbance. Additionally, there are a myriad benefits that can arise from more perennial, edible plants in areas where people live. The plants: 1) increase food security/sovereignty, 2) improve soil quality and capacity to absorb water, 3) sequester carbon dioxide, 4) provided habitat for other organisms, 5) create social opportunities for learning, income, physical activity, and community engagement.
The Michigan State University – Detroit Partnership for Food, Learning, and Innovation is an urban agriculture center in Detroit that has over 45 different varieties of fruits and nuts. The site serves as a model and learning space for integrating fruit crops into community spaces and studying best practices for production.
The Impact of Ivette Perfecto: Changing Realities in Different Social and Environmental
Contexts
Iracenir Dos Santos