PSW 2484 The Convergent Evolution of Agriculture in Ants | Ted Schultz

Lecture Starts at 12:02
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PSW #2484
November 3, 2023
The Convergent Evolution of Agriculture in Ants
Ted Schultz
National Museum of Natural History
Smithsonian Institution

Agriculture is a particular form of mutualistic symbiosis. During the past 12,000 years, it has arisen in humans as many as 23 times. During the past 66 million years, it has also arisen in non-human animals at least 20 times and in insects at least 15 times, most notably in ants, termites, and ambrosia beetles. It is much more likely that these independent origins represent similar solutions to the challenge of growing food than that they are purely due to chance.

The lecture will focus on the most well-studied of the non-human systems, fungus-farming ants, a group of 251 species that occur only in North, Central, and South America and the Caribbean, with the highest concentration in tropical South America. The most familiar fungus-farming ants, leaf-cutting ants, have colony sizes of 5 million or more individuals and are the major herbivores of the Neotropics, and they are the most highly eusocial of all social insects.

Aside from a few species of leaf-cutting ants, which are major pests of human agriculture, the biology of the majority of fungus-farming ants is poorly known, as are the identities of the fungi that they cultivate. Thanks to intensive field work by a number of researchers during the past 35 years, and to recent advances in genome sequencing, this situation has begun to change.

The lecture will summarize the general biology of fungus-farming ants and their fungal cultivars, as well as of other microbial symbionts that are part of the system. The evolutionary histories of ants and fungi will be compared, with implications for reconstructing sequential ant-fungus coevolution. The many similarities between the origins and evolution of human and ant agriculture will be compared and discussed. For example, many of the fungi cultivated by ants appear to be capable of living freely apart from ants at no cost to their fitness, whereas other fungi appear to be unable to do so, suggesting a parallel with the domesticated cultivars of humans. In a parallel with modern industrial human agriculture, the agriculture practiced by leaf-cutting ants creates entire agro-ecosystems, strongly impacting local environments and supporting communities of thousands of species of animals, plants, fungi, and bacteria.

A better understanding of the evolutionary and ecological mechanisms that drive both human and non-human agriculture could lead to the improvement of human agricultural methods. Over vast time spans leaf-cutting ants have, after all, sustainably propagated a single, possibly asexual fungal species; managed an ever-present, evolving microfungal crop disease; and sustainably managed the trees and grasses on which they forage in their local environments.

Ted R. Schultz is a research entomologist and former chair of the Department of Entomology in the Smithsonian Institution National Museum of Natural History, and he also is Adjunct Professor of Entomology at the University of Maryland in College Park. Before joining the Smithsonian he had a peripatetic working life, as a freelance writer, editor, copy editor, proofreader, graphic designer, illustrator, printer, newspaper and magazine production artist, artist, copy camera operator, jewelry maker, cab driver, bartender, dental technician, and dishwasher, among a variety of other jobs.

Ted’s research focuses on the evolutionary history of ants using phylogenomic and fossil data. His interests include all 15,000 extant ant species but he is particularly focused on a group of around 250 species that began farming fungi for food around 66 million years ago. His research has taken him on 32 field expeditions, excavating the nests of fungus-farming ants in 11 South and Central American countries, including 15 trips to diverse locations in Brazil.

He is author on over 120 publications and is an author or editor of four books, including (with Gawne and Peregrine) The Convergent Evolution of Agriculture in Insects and Humans (MIT Press). He also is the author of The Fringes of Reason: A Whole Earth Catalog of New Age Frontiers, Unusual Beliefs, and Eccentric Sciences (Crown/Harmony Books). Ted has appeared in a number of nature documentaries including Evolution: A Journey to Where We’re From and Where We’re Going (WGBH/NOVA and Blue Sky Productions). While at the Smithsonian Ted served on the core design teams of the exhibits, “Partners in Evolution: Butterflies and Plants” and “Farmers, Warriors, Builders: The Hidden Life of Ants”.

Among other honors and awards, Ted has been elected as a Fellow of the American Association for the Advancement of Science.

Ted earned a BS in Biology at UC Berkeley, and a PhD Entomology at Cornell University.

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