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El Nin˜o, Host Plant Growth, and Migratory Butterfly Abundance in a Changing Climate

Robert B. Srygley, Robert Dudley, Evandro G. Oliveira, Andre J. Riveros
Biotropica 2014 v.46 no.1 pp. 90-97
Artocarpus altilis, Brosimum alicastrum, El Nino, Ficus, La Nina, butterflies, climate change, dry season, food plants, leaf development, leaves, lianas, migratory behavior, oceans, photosynthetically active radiation, plant growth, population density, rain, surface temperature, trees, tropical forests, tropics, Pacific Ocean, Panama
In the wet forests of Panama, El Ni~no typically brings a more prolonged and severe dry season. Interestingly, many trees and lianas that comprise the wet forests increase their productivity as a response to El Ni~no. Here, we quantify the abundance of migrating Marpesia chiron butterflies over 17 yr and the production of new leaves of their hostplants over 9 yr to test the generality of the El Ni~no migration syndrome, i.e., whether increased abundance of migrating insects and productivity of their food plants are associated with El Ni~no and La Ni~na events. We find that the quantity of M. chiron migrating across the Panama Canal was directly proportional to the sea surface temperature (SST) anomaly of the Pacific Ocean, which characterizes El Ni~no and La Ni~na events. We also find that production of new leaves by its larval host trees, namely Brosimum alicastrum, Artocarpus altilis, and Ficus citrifolia, was directly proportional to the SST anomaly, with greater leaf flushing occurring during the period of the annual butterfly migration that followed an El Ni~no event. Combining these and our previously published results for the migratory butterfly Aphrissa statira and its host lianas, we conclude that dry season rainfall and photosynthetically active radiation can serve as primary drivers of larval food production and insect population outbreaks in Neotropical wet forests, with drier years resulting in enhanced plant productivity and herbivore abundance. Insect populations should closely track changes in both frequency and amplitude of the El Ni~no Southern Oscillation with climate change.