Wednesday, 16 August 2017

Learning from lizards: St. Louis native studies evolution in real time - via Herp Digest

by Jane Henderson, St. Louis Post Dispatch, 8/11/17
For additional photos and video go to http://bit.ly/2uDVWxE

Thank a cranky reptile for helping set a St. Louis boy on the road to Harvard.

Jonathan B. Losos went from carrying plastic dinosaurs to school to begging his parents for a pet caiman, those cousins of alligators that in the early 1970s could be bought in a neighborhood pet store.

“I had to wear ski gloves so I wouldn’t get bit,” he says

Undeterred, Losos kept two caimans in a horse trough in the backyard of his family’s Ladue home. During the winter, the scaly chompers were moved to the basement, outfitted with a plastic swimming pool and sun lamp.

In his new book, Losos writes that he got the idea from an episode of “Leave It to Beaver,” when Wally and the Beave hid a baby alligator in the bathroom.

At least the pre-adolescent Losos asked his parents. And because they were friends with Charles Hoessle, then deputy director of the St. Louis Zoo, they queried the professional herpetologist about what he thought. He thought it a superb idea.

“My mother was stuck, and soon our basement was full of all manner of reptile,” Losos writes. “I was on my way to my own career in the field.”

In fact his mother, Carolyn Losos, felt sorry for the single caiman and got a second one so it had company. But she drew the line at snakes.

Now a professor, researcher and curator of herpetology at Harvard’s Museum of Comparative Zoology, Losos, 55, tells a few stories about himself in “Improbable Destinies: Fate, Chance, and the Future of Evolution.” He’ll talk more about his book Thursday at St. Louis County Library.

An expert in evolutionary biology, he writes accessibly about the field today.
In short, Darwin notwithstanding, scientists can observe evolution as it happens. And it can happen quickly. It doesn’t take millennia as the great Victorian believed.

“You can see evolution with bacteria in a matter of days,” Losos says.

With guppies, a couple of years are enough to see them evolve: Research has shown that male guppies not threatened by predators soon develop more color, such as blue and iridescent spots.

Fish exposed to polluted rivers have evolved so they can live there. And wild elephants may even be changing to favor smaller tusks — a possible result of hunters’ poaching the magnificent beasts for ivory.

Most of these cases and more are described in “Improbable Destinies,” an interesting title because some of the examples seem quite probable. Others, however, are curious and perhaps unknowable — for instance, would humans have evolved if an asteroid hadn’t wiped out dinosaurs millions of years ago?

Evolutionary biology is like a detective story, with researchers looking at historic clues, Losos writes.

But today’s scientists also use lab experiments, DNA sequencing and fieldwork to learn about evolution: “Indeed, with the flood of genetic data now available for so many different species, our understanding of evolutionary relationships is advancing by leaps and bounds, producing a much firmer grasp on the evolutionary tree of life.”

It was only 1980 when a study of guppies was published that helped show scientists that evolutionary biology could be an experimental science in natural settings.

Guppies in Trinidad have inspired several scientists, and Losos writes about the studies in detail. Most of his book is about a variety of researchers, but the chapter about lizards, particularly brown anoles, is much his own and is a great example of speedy evolution and what biologists call “convergence.” That means that similar species in different places (without interbreeding) evolve some of the same traits.

For the lay reader, one of the most amusing parts of his story is how Losos catches lizards to measure their legs and look at other attributes — such as the large, sticky toe pads that allow some to run up slick, vertical slopes like green or brown Spider-Men.

The scientist uses a fishing rod with a loop at the end made out of dental floss (preferably waxed). He approaches the anoles in the wild slowly, then with a quick flick snares the subject around the neck with the dental floss noose. It tightens but doesn’t hurt the lizards, which have strong necks, he says.

What Losos found was that on various Caribbean islands, separate communities of lizards evolved in similar ways without any contact. Some that lived closer to the ground had longer legs to run quickly over wide surfaces. Others, which lived up higher on narrow twigs, had shorter legs to grasp small branches more easily.

Losos and colleagues X-rayed lizard legs to get precise measurements, then returned them to the exact place where they were caught. Much work was done on the islands, but some lizard Olympics were also held in labs to study how quickly the mini-athletes moved on various surfaces.

When talking to scientists about the work, he writes, sometimes pesky botanists ask whether the leg changes actually showed genetic change, or could lizards born on islands with slim vegetation simply have grown shorter legs? (The question refers to “phenotypic plasticity,” such as plant growth that responds strongly to different conditions.)

Losos and his colleagues studied the research. He writes about how human weightlifters have thicker arm bones, “a plastic trait” affected by behavior. Those musclebound subjects don’t, however, have children who inherit thicker arm bones. And some of the lizards’ bones were longer, a trait that studies on exercise usually didn’t explain.

Still, Losos did more work in the lab with lizard leg growth and found that, indeed, a small amount of the growth could be attributed to phenotypic plasticity. But he concluded that evolved genetic change was “likely responsible” for most of it, and he believes that in the next few years researchers will identify the relevant genes involved.

In 1997, Losos’ studies were reported in The New York Times, which wrote that “a remarkable experiment with lizards in the Bahamas has now shown that evolution moves in predictable ways and can occur so rapidly that changes emerge in as little as a decade or so.”

Dr. Douglas J. Futuyma, an evolutionary biologist at the State University of New York at Stony Brook, was quoted saying the study was “distinctive and exciting and one that will be cited for many years to come.”

Losos says work in the Bahamas isn’t quite as paradisiacal as it sounds. For one thing, hurricanes occasionally wiped out his lizard subjects (some communities amazingly recovered, though, when their eggs survived hours underwater). When not traveling, during the school year, he lives in the Boston area near Harvard University. His wife, Melissa, and two cats remain in their Ladue home, where he spends summers.

One of his favorite places to visit is actually Australia, which has great biodiversity and his favorite animal, the duckbill platypus. At age 7, Losos was angry when his parents, Joseph and Carolyn Losos, went to Australia without him (they did bring him back a stuffed toy platypus).

In fact, here it might be pertinent to note that although Losos seemed to be born interested in reptiles, his environment nurtured his hobby: He grew up in a family that traveled extensively, and his science teachers at Ladue’s high school gave him a great education, he says.

Joseph Losos, a graduate of Harvard University, is a retired investment adviser and a commissioner for the St. Louis Zoo; he has also written book reviews for the Post-Dispatch. Carolyn Losos, a longtime activist in many St. Louis organizations, such as Focus St. Louis, is on the executive committee of the Missouri Botanical Garden and is chairwoman of Arts & Faith St. Louis.

As much as environment plays a role in development, biologists can’t always explain, though, whether it is the deciding factor in evolution.

That platypus, for example is a one-off animal — an “evolutionary singleton” despite living in streams and environmental conditions that can be found in other countries. (It does, though, have attributes that other animals have, so Losos writes that it is both “a paragon and a repudiation of convergence, evolutionarily unique, but a composite of convergent traits.”)

“Who would have predicted the duckbill platypus?” Losos says, alluding to the book’s title, “Improbable Destinies.”

Other evolutionary singletons include chameleons, kiwis and humans, all of which are unlikely to have evolved elsewhere (including other planets). Losos thinks, in fact, that if an asteroid had not eliminated dinosaurs, there would not be today’s homo sapiens. Variations on a “dinosauroid” have been proposed, a creature that evolved with a big brain, feathers, a tail and hands.

Speculations may not make the case for today’s study of evolution. But there are other examples of practical applications. In particular, the study of how microbes can so easily evolve to evade antibiotics and pesticides.

If scientists pinpoint important ways bacteria and viruses evolve, they may find techniques to keep microbes from foiling public health efforts. As Losos says: “It turns out evolution is important in the world today.”

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