Lincoln Brower - US grants

Every autumn, up to a billion monarch butterflies across most of eastern North America migrate south to the mountains of Mexico. By the tens of millions they cluster in forests on a handful of acres. These high altitude sites have few flowers on which butterflies can feed, so the butterflies must stay cold to slow their expenditure of the energy reserves (lipids) they accumulated during their migration. The sites are subject to severe winter storms, and the forest canopy serves as a protective blanket and umbrella. In this project, cold tolerance experiments and lipid analyses will develop a stronger picture of how climate affects both butterfly survival and the rate at which individuals deplete their energy reserves. Detailed studies of microclimate within colonies and in nearby sites not selected by the butterflies will help explain why the butterflies are so selective in their habitat use. Using aerial reconnaissance and satellite imagery, exploration will search for additional overwintering areas in forests identified as having suitable microclimate. Geographic information system (GIS) analysis will integrate all of these components to determine the current extent of suitable habitat, and will quantify how suitable habitat has changed over the past forty years.
Humans are altering the forests where the monarchs overwinter, through logging, fires and ecotourism. The longterm persistence of the monarchs' unique migration depends upon the persistence of appropriate wintering sites. This research has conservation implications, therefore, for scientists, policymakers and citizens concerned about this extraordinary wildlife spectacle.

In the last half century the monarch butterfly, Danaus plexippus, has become an important model organism for research on mimicry, plant-herbivore interactions, chemical ecology, physiological ecology, and migration. In addition, the charismatic insect has proven to be an appealing entry point into the world of science for both children and adults. Much of the research that has made this a model organism has been conducted by Lincoln Brower, who will be supported to write a book targeted to scientists, graduate and undergraduate students, and science-curious general readers. The book will address the monarch butterflies' chemical defense against predators, the ecological chemistry of the butterflies' interactions with their milkweed hostplants, the physiology, ecology and behavior of the butterflies as they cope with the microclimate in their Mexican wintering sites, and the butterflies' unique migration and wintering biology that illustrate timely conservation issues. The intellectual merit of the book for scientists will be in its presentation of data, critical review of evidence, and extensive bibliography.

An important broader impact of the project will be the archiving of original datasets in a digital data registry. Explanations of the significance of these data and including unanswered questions in each chapter will help to spark new research. The book will enhance non-specialists' and students' understanding of diverse methodologies that can be used to address ecological questions, and their appreciation of the value of long-term studies and the collaborative nature of many discoveries. Copious illustrations will engage the reader and tell the story, so that the non-expert is prepared to understand data and how experiments in both the field and laboratory were actually conducted.