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Panel discussion

Janzen-Connell 50th Anniversary:

Where Are We?

Fri, July 23, 14:30 hrs (UTC±00:00)

The exuberant physiognomy of tropical forests is largely imparted by the astonishing diversity of their predominant life form—trees. What maintains such tree diversity? Numerous ideas and hypotheses have been proposed to examine and explain that question, but none of them has been as influential, stimulating and productive as the now commonly known Janzen-Connell Hypothesis (JCH). Fifty years after the publication of the landmark papers by Dan Janzen and Joe Connell, this idea is still very much relevant, and important for us to reflect on where we are in our understanding of this fundamental question, and the role JCH has played in it. In this panel, three prominent ecologists, Lissy Coley, John Terborgh, and Dan Janzen himself will present their perspectives on the significance, remaining knowledge lacunae, and future avenues in the study of the maintenance of tropical forests in the context of JCH. Hopefully, the legacy of JCH will not only continue to fuel our collective aspiration to understand tropical biodiversity but will also help us reflect and act on the urgency of its conservation given the challenges of the Anthropocene.


Rodolfo Dirzo's scientific work examines species interactions in tropical ecosystems from  Latin America, Africa, the Central Pacific, and other tropical areas of the world. Some of his research highlights the decline of animal life (“defaunation”), and how this affects ecosystem processes/services (e.g. disease regulation). He teaches ecology, natural history, conservation biology, and bio-cultural diversity at undergraduate and graduate levels at Stanford, and conduct science education programs with underserved children in the Bay Area and his other research sites, and he co-authored the new Framework for K-12 Science Education in the USA. He is member of the Mexican Academy of Sciences, the USA National Academy of Sciences, and the American Academy of Arts and Sciences.


Liza Comita is a Professor of Tropical Forest Ecology in the School of the Environment at Yale University. She is also a Research Associate at the Smithsonian Tropical Research Institute and co-director of the Yale Center for Natural Carbon Capture. Her research examines ecological mechanisms that shape patterns of plant diversity, dynamics, and species distributions in tropical forests. In particular, her work focuses on how biotic interactions (e.g., natural enemies) and abiotic factors (e.g., drought) shape tropical tree communities by influencing spatial and temporal patterns of seedling and sapling growth and survival in the forest understory.


John Terborgh is James B. Duke Professor Emeritus of Environmental Science in Duke University and has current affiliations with the University of Florida – Gainesville and James Cook University, Cairns, Australia. His work focuses on tropical ecology, particularly plant-animal interactions and trophic cascades. He has conducted research in the West Indies, South America, Africa, Malaysia, and New Guinea and has published more than 300 articles and 8 books. He is a member of the American Academy of Arts and Sciences and the National Academy of Sciences. He was awarded a Pew Fellowship In 1992 and became a MacArthur Fellow in the same year. He was awarded the Daniel Geraud Elliot Medal by the National Academy of Sciences in 1996. He has served on the boards of numerous conservation organizations and in 1999 he founded ParksWatch, an organization dedicated to monitoring and publicizing the status of parks in developing countries. He has remained active in research and conservation to the present.


Phyllis (Lissy) Coley is a Distinguished Professor at the University of Utah, a Research Associate of the Smithsonian Tropical Research Institute and a Fellow of the Ecological Society and the American Academy of Arts and Sciences. Her career has focused on plant anti-herbivore defenses in rainforests throughout the tropics, because biotic interactions have played a particularly strong role in shaping tropical communities. Her early research quantified patterns of plant defenses and tried to understand how selection may have favored different defense investments in species of different life histories and habitats (e.g. 'resource availability theory'). She has also used physiological approaches to examine the costs and benefits of defense as well as the adaptations of plants to life in the understory. A major current focus in her lab is to characterize chemical defenses (metabolomics) and link these to other plant traits and to herbivore host choice. This work focuses on the speciose and widespread tropical tree genus Inga (Fabaceae) as a model to understand how herbivores may be driving rapid evolution of defenses and how this might contribute to community assembly and speciation in the genus. She also established a multimillion dollar bioprospecting program in Panama which has made a major impact on both science and conservation.


Daniel Janzen is DiMaura Professor of Conservation Biology, University of Pennsylvania, Philadelphia, USA, and Technical Advisor to Área de Conservación Guanacaste (ACG). ACG is a 169,000-hectare government/private hybrid Conservation Area in northwestern Costa Rica. He is a tropical ecologist and biodiversity conservationist with 66 years of field experience and 466 scientific papers and books, all focused on the interactions of tropical animals and plants, and for the past 25 years, on their permanent in-situ conservation as well ( He is a world level authority on the taxonomy and biology of tropical caterpillars, and is a member of the US and the Costa Rican National Academy of Sciences, and recipient of the Crafoord Prize (1984), the Kyoto Prize (1997), and BBVA Prize (2012). He and his biologist wife Dr. Winnie Hallwachs ( are co-architects and co-constructors, along with hundreds of others, of ACG and of Costa Rica's INBio (Instituto Nacional de Biodiversidad), and of Costa Rica's Iniciativa Paz con la Naturaleza (IPN) (2006-2010), which morphed into Costa Rica Forever. He is President of the Guanacaste Dry Forest Conservation Fund (GDFCF;, the US-based NGO for ACG. He and Hallwachs are currently focused on facilitating the International Barcode of Life (iBOL) efforts to DNA barcode all species of the world for their identification and species discovery by anyone anywhere at any time, and simultaneously, on facilitating Costa Rica's willingness to permanently conserve the 4% of the world's biodiversity that lives on 25% of Costa Rican national terrain and sea, and do it as a global example of sustainable non-damaging use of tropical wildland biodiversity.

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