Bruce S. Grant - Observing Evolution: Peppered Moths and the Discovery of Parallel Melanism

OBSERVING EVOLUTION

Peppered Moths and the Discovery of Parallel Melanism

Bruce S. Grant

Johns Hopkins University Press

Baltimore

2021 Johns Hopkins University Press

All rights reserved. Published 2021

Printed in the United States of America on acid-free paper

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Library of Congress Cataloging-in-Publication Data

Names: Grant, Bruce S., 1942 author.

Title: Observing evolution : Peppered moths and the discovery of parallel melanism / Bruce S. Grant

Description: Baltimore, Maryland : Johns Hopkins University Press, [2021] | Includes bibliographical references and index.

Identifiers: LCCN 2020046103 | ISBN 9781421441658 (hardcover) | ISBN 9781421441665 (ebook)

Subjects: LCSH: Peppered moth. | Melanism.

Classification: LCC QL561.G6 G73 2021 | DDC 595.78dc23

LC record available at https://lccn.loc.gov/2020046103

A catalog record for this book is available from the British Library.

Photographs: Unless otherwise credited, all photos are from the author.

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To the memory of my mentor, Professor Donald D. Rabb

When I retired in 2001 after teaching in the Biology Department at the College of William & Mary for 33 years, one of my colleagues cheerfully said, And now you wont have to do any more research, to which I expressed horror. What? Why on earth would I want to quit doing research? I should have left it there, but I went on scolding, insisting that (1) the people we hire do research, whether or not they are paid to; (2) they are motivated by curiosity; and (3) they do it because its fun. Its the best game in town.

Of course, unlike my colleague, I didnt require a cyclotron to carry on. All I needed was a bright light bulb to attract moths.

For the first third of my career, I was a lab-bound geneticist who worked on fruit flies. Then I switched to tiny parasitoid wasps to explore other questions. I didnt fall in love with my research critters until I became a moth trapper in 1983. That conversion didnt happen because I was attracted to moths, in the same way some people find enjoyment in butterflies or birds. I was driven to more deeply explore the phenomenon known as industrial melanism (dark coloration evolving in animals living in places affected by industrial pollution), a topic quite familiar to biology students worldwide. Nonetheless, there were still questions to be answered, and new ones to be asked. I became immersed in this research and remain so to this day.

The work took me around the world. In this book I describe my experiences and the remarkable people I met along the way. I tell their stories, including my own daily exploits. But not as a tourist. While travel far from home for extended periods is part of my Methods & Materials, the book itself is about the scientific discovery of parallel evolutionthe rise and fall of melanic (black) peppered moths on separate continents. My route to this discovery was a circuitous one, often barking up the wrong tree. Thus this is an adventure story, offering a firsthand account of the history of this research.

While I have intentionally aimed this book at a broad audience, professional evolutionary biologists will, I hope, find it sound and intellectually satisfying. For those especially interested in going beyond my narrative, I have included a substantial bibliography that contains sources for further information. General readers can safely skip the bibliography, in the knowledge that all claims made in the book are supported by extensive, peer-reviewed literature.

Most of all, I hope readers will enjoy learning about how evolution is studied as an observable, ongoing process. Its all around us.

Acknowledgments are typically filled with lists of names, along with the various contributions people have made to published projects. My whole book is a means of giving credit to and thanking the individuals who have made the work possible. These are the same people I met along the way while pursuing research with peppered moths. They are the cast of charactersmy colleagues, collaborators, and friends. This volume tells their stories. Their names appear in the following pages.

But yes, some people deserve special mention. Jim Murray, in particular, started me on this quest. My wife, Cathy, and our two daughters, Megan and Elspeth, were my field hands, critics, companions, and sources of great joy. They remain in those starring roles.

My long-time colleague and fellow moth trapper, Larry Wiseman, read the complete book manuscript in two days. I took that as a compliment. He has unstintingly provided me with encouragement and advice. Steven Orzack, another dear friend, volunteered to serve as an unofficial literary agent. He recruited fellow evolutionary biologist Richard Gawne as a voluntary reviewer. I was touched by their support and benefited from their constructive criticisms. I also owe thanks for reference assistance to Mary A. B. Sears of the Ernst Mayr Library at Harvard Universitys Museum of Comparative Zoology.

Most certainly I have failed to mention individuals in this book who have helped me in numerous ways. These include people who permitted me to operate moth traps on their property. Jewel Thomas maintained livestock during my extended absences from Williamsburg and provided photographic services. The esteemed neurologist Lloyd Guth, MD, collaborated on a pilot study assessing altered pH of food plants on larval survival. I apologize to those students who worked in my moth lab but whose names didnt make it into this narrative. They include Leslie Crabtree, Annie Harvilicz, Kathleen Huffman, Wenda Smith Ribeiro, Heather Scott, and Dan Stimson. Their efforts advanced my understanding of peppered moths.

Anonymous reviewers provided detailed suggestions and spotted my blunders. I am very grateful for the time they have generously invested to help me succeed. I am especially indebted to Tiffany Gasbarrini, senior acquisitions editor at Johns Hopkins University Press, for her welcoming reception of this project and thoughtful guidance throughout. Kathleen Capels taught me what expert copyediting is all about. For her careful scrutiny of the entire production, sincere thanks are owed to production editor Hilary Jacqmin. I am very fortunate to have such talented people in my corner. Whatever errors remain in this book are mine.

Charles Darwins On the Origin of Species (published in 1859) is, in essence, a book on the origin of adaptations. The process by which adaptations are fashionedaccording to Darwins long argumentis natural selection. During Darwins own time, natural selection was regarded as a process that was too slow to observe directly, step by step, as it occurred. Evolution was studied as a history, rather than an ongoing process. Times have changed. Natural selection is now witnessed routinely. In some instances, significant changes occur with astonishing speed, such as the evolution of antibiotic resistance in bacteria, or pesticide resistance in insects, or changes in bill dimensions in Galpagos finches. The first and best-known example of observable natural selection traces its beginnings to the decade before Charles Darwin published his most profound book, and this example was explained in full Darwinian terms just 14 years after Darwins death. The evolution of melanism in