Lizards shed light on species diversity

Some people are drawn to majestic racehorses, melodious songbirds, or cuddly puppies. Jonathan Losos has had a lifelong love affair with reptiles.

As a youngster in suburban St. Louis, the Harvard professor was a “little dinosaur freak,” bringing bucketfuls of the molded plastic beasts to nursery school.

Inspired in fifth grade by a “Leave It to Beaver” rerun wherein “the Beav” procures a baby alligator from Captain Jack’s Alligator Farm, Jonathan asked his mother for a pet caiman, a Central and South American relative of the alligator. In a valiant effort to tamp down the idea, Mrs. Losos suggested he seek the advice of a family friend who happened to be deputy director of the local zoo. The tactic failed miserably when the friend, a zoologist with his own soft spot for reptiles, surprised everyone by replying that he thought it was a fine idea.

“My mom was out of luck,” Losos says, and over the next eight years various caimans cohabited with the Losos clan. “The rest is history.”

Today Losos, 45, is a biologist who uses the stunning array of Anolis lizards resident on Caribbean islands to explain the causes and consequences of evolutionary diversification. He joined the Harvard faculty last year as Monique and Philip Lehner Professor for the Study of Latin America, professor of organismic and evolutionary biology, and curator in herpetology at the Harvard Museum of Comparative Zoology.

Frequently a retrospective discipline, “evolutionary biology is more like the study of history than, say, chemistry,” Losos says. “More colloquially, I like to compare being an evolutionary biologist to being a detective: both involve using the clues available to fashion the best case of whodunit.”

Anoles, as the lizards Losos tracks are called, are small insectivores abundant on islands throughout the Caribbean. These lizards are a textbook model of biodiversity: abundant and easy to study, with more than 400 known species, a number that grows each year. Among birds, reptiles, and mammals, Anolis is the most species-rich genus.

One of the most fascinating things about anoles for Losos and other evolutionary biologists is that highly similar species of specialized lizards have arisen, apparently independently, on numerous Caribbean islands.

“If you were to go to any of the islands of the Greater Antilles — Cuba, Hispaniola, Jamaica, or Puerto Rico — you would see a variety of different species,” Losos says. “Go, for example, to the Luquillo Mountains of Puerto Rico and sit quietly in the rain forest. After a few minutes, you will start to see lizards with long legs running and jumping near the ground, others with large toepads high in the trees, and yet others with narrow bodies and short limbs crawling carefully on narrow surfaces.”

Remarkably, Losos says, essentially the same set of habitat specialists exists on each of the islands. On any of the other islands of the Greater Antilles you would find a lizard that closely resembles the Puerto Rican twig-dweller, living in a similar habitat and behaving identically. The same would hold true for lizards that have evolved on each island in tree canopies, on tree trunks, or in low-lying vegetation.

A primary focus of Losos’ anole research has been the mechanistic links between lizard morphology and their habitat. He studies how bodily variations confer different physical abilities that conform to the lizards’ specific niches.

“This is where the fun comes in,” Losos says. “Measuring lizard functional abilities is much like orchestrating a Lizard Olympics because individuals are put through their paces to determine how fast they can run, how far they can jump, and how well they can cling, among other events.”

Losos’ group uses some specialized athletic venues: A lizard racetrack, two meters long with infrared detectors placed every quarter-meter, traces the animals’ speed as they race toward the safety of a dark bag placed at the “finish line.” Lizard stick-to-itiveness is assessed with a plate that measures the force of the creatures’ toepads as a scientist attempts to pull them free. For the lizard long jump, Losos places an anole on a flat board 30 centimeters above the ground and taps its tail, yielding a real-life leaping lizard.

Although Losos’ move last year to Harvard prompted his departure from his hometown, where he had been on the faculty of Washington University since 1992, it was an exciting homecoming of sorts for the 1984 College alumnus. (All three of Losos’ younger sisters also graduated from Harvard.)

Losos entered Harvard in 1980 thinking he might like to study animal behavior, until he crossed paths with evolution luminaries E.O. Wilson and the late Stephen Jay Gould. Enrolled in back-to-back Core courses taught by that dynamic duo, Losos says the first semester of his freshman year “really launched me” into the field of evolutionary ecology.

He became a volunteer at the Museum of Comparative Zoology (MCZ), joining the laboratory of herpetologist Ernest Williams, who had in the 1960s and 1970s established anoles as a key model for studies of evolution and ecology.

“He was a remarkable scientist, really ahead of his time,” Losos says. “Many of today’s leaders in the fields of ecology and evolution were his grad students and have roots in his group. It’s somewhat daunting to return to Harvard and the MCZ to fill his footsteps.”

It was during this time that Losos learned the joys of fieldwork. He spent the summer after his sophomore year in Jamaica collecting anoles with Gregory Mayer, one of Williams’ graduate students, and was dazzled by the diversity of reptiles on the island.

It’s a practice Losos continues today. He spends two weeks to three months a year doing fieldwork, and while his focus in recent years has been the Caribbean, he has also conducted research in Australia, Costa Rica, Madagascar, and South Africa. This off-site research is complemented by genetic analysis when he is back in the lab.

While visiting the tropics might seem an enviable line of work, the brief interludes spent pursuing lizards in the wild are intense, Losos says — not at all what he expected before that first undergraduate visit to Jamaica, when he asked a labmate if he should bring his tennis racket.

When he’s not in warmer climes scouting out lizards, Losos hits the ice for recreational hockey. “It’s a league for people who play badly, for which I am increasingly well qualified,” he says.

Losos was drawn back to Harvard by the resurgent Department of Organismic and Evolutionary Biology and the MCZ, which holds Ernest Williams’ collection of 41,000 anoles. “To be here with this fabulous collection is just wonderful,” he says.

He credits MCZ director James Hanken with moving the museum in exciting new directions, and hopes to play a role in Hanken’s efforts to boost MCZ accessibility and develop its collections into a community resource.

The Monique and Philip Lehner Professorship for the Study of Latin America, now held by Losos, was created in 1999 by the Lehners to support the David Rockefeller Center for Latin American Studies (DRCLAS). It can be allocated by the FAS dean to any department in consultation with DRCLAS. Philip Lehner ’46, A.M.P. ’69 is chairman and CEO of Leigh Fibers Inc.; Monique Lehner is a consultant specializing in historic preservation.