Stephan Halloy was conducting surveys on vegetation and wildlife on the excessive plateaus round San Miguel de Tucumán in northwestern Argentina within the 1970s when he first encountered lizard Popsicles.
The mountains across the Argentine metropolis climb quickly to elevations of 13,000 to 16,400 toes, packing a mess of ecological niches into a comparatively small space. The plateaus on the prime might be sizzling within the afternoon, however rapidly drop to beneath freezing at night time — not precisely the kind of place you’d anticipate finding a lizard.
Nonetheless, Dr. Halloy, now a senior adviser with the New Zealand Ministry for Primary Industries, caught a number of and positioned them in a field exterior his tent in a single day. “When I opened the box the next morning they were hard as wood — you couldn’t bend them,” Dr. Halloy recalled just lately. “They looked absolutely dead.”
But as soon as the solar got here up, the lizards started to thaw and have been quickly operating round within the field similar to regular.
“Obviously I found that very surprising,” Dr. Halloy stated.
In the 1990s, Robert Espinoza, a biologist at California State University, Northridge, heard this story from Dr. Halloy, and he has been learning lizard Popsicles ever since. The lizards belong to the genus Liolaemus, and analysis by Dr. Espinoza and his colleagues has revealed that the lizards are indisputably the good on the planet. Whereas tropical lizards like iguanas fall from timber when it will get chilly, Liolaemus can supercool their our bodies, tolerate freezing and reside farther south and at greater elevations than some other recognized lizard species.
“They’re real record holders,” Dr. Espinoza stated.
Liolaemus species have been discovered on the island of Tierra del Fuego, on the southern finish of the Americas, and one researcher has even heard tales of them strolling on Perito Moreno, a glacier in Patagonia. Most Liolaemus are present in Argentina and Chile, though some are discovered as far north as Peru. Containing greater than 272 documented species, Liolaemus is the second-largest genus amongst all mammals, birds and reptiles, after solely anoles, one other sort of lizard.
Dr. Espinoza remains to be investigating how these lizards survive such chilly climates. In one experiment, his staff fitted fashions of lizards, made from hole copper, with temperature loggers and positioned them at one space at 13,369 toes in Salta Province. The fashions recorded temperatures as little as minus 11.2 levels Fahrenheit on the floor and 15.8 Fahrenheit underground. (The lizards normally spend the night time in burrows.)
The staff then examined the chilly diversifications of six species from various elevations. They discovered that some may survive cooling as little as 21.2 levels Fahrenheit, though Dr. Espinoza suspects that wild lizards can stand up to colder temperatures. Liolaemus huasihuasicus, the species that Dr. Halloy initially encountered, lives on a mountain about 1,640 toes greater than the very best species Dr. Espinoza checked out — a presumably colder space.
Dr. Halloy famous in a 1989 publication that Liolaemus huasihuasicus may survive freezing at 14 levels Fahrenheit, however solely when at an elevation of 13,944 toes; the lizards died when cooled to 26.6 levels Fahrenheit at exams carried out at 1,476 toes.
Dr. Espinoza and his co-authors discovered that Liolaemus lizards have tailored skills to cope with the chilly via three mechanisms. Some lizards keep away from excessive chilly by going underground. Others use a strategy of supercooling; by staying fully nonetheless, they will enable their our bodies to drop beneath freezing with out truly freezing strong. Finally, some can even tolerate full-body freezing for brief durations of time. Dr. Espinoza stated that some Liolaemus species probably made use of multiple mechanism, relying on the situations.
The technique of full-body freezing is probably going much like that seen in North American wooden frogs, which keep frozen over winter because of an antifreeze-like glucose answer that protects the cells; Dr. Espinoza nonetheless wants to analyze this speculation to make sure. The world’s southernmost gecko, Darwin’s marked gecko, one other Argentine lizard that Dr. Espinoza has studied, most probably adopts the supercooling technique.
Lizards of many colours
The motive Liolaemus lizards can stand up to such chilly temperatures and excessive elevations may clarify why there are such a lot of of the lizards. Whereas there have been solely about 50 described to science when Dr. Halloy labored on them within the late 1970s, there are actually 272 species.
Dr. Espinoza and others have found quite a few species, and his occasional co-author Fernando Lobo, a zoologist on the National University of Salta in Argentina, has found 30 or extra species of Liolaemus and its shut cousin, the genus Phymaturus. In one case, Dr. Lobo found a species beneath his tent, in cloudy, frozen climate within the Argentine province of Santa Cruz close to the Chilean border.
“They didn’t look like any of the others,” Dr. Lobo stated. “We suspected they were a new one. We’ve had that excitement dozens of times in these 25 years.”
At the present price of discovery, Liolaemus will probably turn into probably the most quite a few genus of dwelling mammals, reptiles and birds in coming years.
‘A species pump’
The massive variety of Liolaemus species could also be associated to the mountainous area the place they reside, Dr. Espinoza stated. The Andes are comparatively younger — about the identical evolutionary age because the lizards. He believes that because the Andes pushed out of Earth’s crust, the genus splintered into myriad ecological niches that ultimately resulted in new species.
“The Andes are just kind of a species pump creating all these new types,” Dr. Espinoza stated.
Most of the lizards are related in dimension, however they differ significantly in shade and even in weight loss plan and beginning methods. Dr. Lobo associated a narrative about an expedition in Argentina’s Jujuy Province. During their work, an area girl appeared from a small sheep- and llama-herding village within the mountains.
“She told us very clearly which one was which species with their Indian names, and said ‘That one lays eggs and that one gives birth,’” Dr. Lobo stated.
Dr. Espinoza stated that half the lizards give beginning to reside younger, maybe as a result of laying eggs in chilly temperatures is probably going not a recipe for achievement for some species. In 2016 he additionally described a brand new species, Liolaemus parthenos, by which the females reproduce via virgin beginning, with out fertilization from a male.
Melisa Olave, a researcher with Argentina’s National Scientific and Technical Research Council, who heard in regards to the lizards on Perito Moreno, carried out a latest examine displaying that the rise of the Andes might not be the one issue driving Liolaemus evolution and variety. Liolaemus species have very low extinction charges relative to different lizards. Their variation in habitat use, generalist method to weight loss plan — some species are herbivorous whereas others are omnivorous or carnivorous — and completely different types of copy could also be crucial to explaining Liolaemus species’ richness and survival. She stated that being a generalist is often thought-about advantageous, as a result of it’s simpler to seek out appropriate habitats within the extremely diverse landscapes of South America’s southern cone.
In different phrases, the excessive variety of Liolaemus could also be extra a product of low extinction price than of habitat splintering.
Dr. Espinoza agreed that species persistence over time could possibly be a contributing consider species richness, however he additionally believes that alone can’t clarify the range.
In any case, Dr. Olave shares the final sense of marvel infecting lots of the researchers who’ve labored with these lizards.
“Liolaemus species have an extraordinary ability to survive through time,” she stated.