Animals

There’s nothing like a big mass extinction to open up ecological niches and clear out the competition, accelerating evolution for some lucky survivors. Or is there? A new study suggests that the rate of climate change may play just as large a role in speeding up evolution.

The study focuses on reptile evolution across 57 million years — before, during and after the mass extinction at the end of the Permian Period (SN: 12/6/18). That extinction event, triggered by carbon dioxide pumped into the atmosphere and oceans through increased volcanic activity about 252 million years ago, knocked out a whopping 86 percent of Earth’s species. Yet reptiles recovered from the chaos relatively well. Their exploding diversity of species around that time has been widely regarded as a result of their slithering into newly available niches.

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But rapid climate fluctuations were already taking place much earlier in the Permian, and so were surges of reptile diversification, researchers say. Analyzing fossils from 125 reptile species shows that bursts of evolutionary diversity in reptiles were tightly correlated with relatively rapid fluctuations in climate throughout the Permian and millions of years into the next geologic period, the Triassic, researchers report August 19 in Science Advances.

Scientists’ understanding of evolution is expanding as they become more tuned into the connection between it and environmental change, says Jessica Whiteside, a geologist at the University of Southampton in England who works on mass extinctions but was not involved in the new work. “This study is bound to become an important part of that conversation.”

To investigate reptile evolution, evolutionary paleobiologist Tiago Simões of Harvard University and colleagues precisely measured and scanned reptile fossils ranging from 294 million to 237 million years old. In all, the researchers examined 1,000 specimens at 50 research institutions in 20 countries.  For climate data, the team used an existing large database of sea surface temperatures based on oxygen isotope data, extending back 450 million years, published in 2021.

By closely tracking changes in body and head size and shape in so many species, paired with that climate data, the researchers found that the faster the rate of climate change, the faster reptiles evolved. The fastest rate of reptile diversification did not occur at the end-Permian extinction, the team found, but several million years later in the Triassic, when climate change was at its most rapid and global temperatures witheringly hot. Ocean surface temperatures during this time soared to 40° Celsius, or 104⁰ Fahrenheit — about the temperature of a hot tub, says Simões.

A few species did evolve less rapidly than their kin, Simões says. The difference? Size. For instance, reptiles with smaller body sizes are already preadapted to live in rapidly warming climates, he says. Due to their greater surface area to body ratio, “small-bodied reptiles can better exchange heat with their surrounding environment,” so stay relatively cooler than larger animals.

“The smaller reptiles were basically being forced by natural selection to stay the same, while during that same period of time, the large reptiles were being told by natural selection ‘You need to change right away or you’re going to go extinct,’” Simões says.

This phenomenon, called the Lilliput effect, is not a new proposal, Simões says, adding that it’s been well established in marine organisms. “But it’s the first time it’s been quantified in limbed vertebrates across this critical period in Earth’s history.”

Simões and colleagues’ detailed work has refined the complex evolutionary tree for reptiles and their ancestors. But, for now, it’s unclear which played a bigger role in reptile evolution long ago — all those open ecological niches after the end-Permian mass extinction, or the dramatic climate fluctuations outside of the extinction event.

“We cannot say which one was more important,” Simões says. “Without either one, the course of evolution in the Triassic and the rise of reptiles to global dominance in terrestrial ecosystems would have been quite different.”  More

In the upper reaches of the Skykomish River in Washington state, a pioneering team of civil engineers is keeping things cool. Relocated beavers boosted water storage and lowered stream temperatures, indicating such schemes could be an effective tool to mitigate some of the effects of climate change.

In just one year after their arrival, the new recruits brought average water temperatures down by about 2 degrees Celsius and raised water tables as much as about 30 centimeters, researchers report in the July Ecosphere. While researchers have discussed beaver dams as a means to restore streams and bulk up groundwater, the effects following a large, targeted relocation had been relatively unknown (SN: 3/26/21).

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“That water storage is so critical during the drier periods, because that’s what can keep the ecosystem resilient to droughts and fires,” says Emily Fairfax, an ecohydrologist at California State University Channel Islands in Camarillo who was not involved with the study.

The Skykomish River flows down the west side of Washington’s Cascade Mountains. Climate change is already transforming the region’s hydrology: The snowpack is shrinking, and snowfall is turning to rain, which drains quickly. Waters are also warming, which is bad news for salmon populations that struggle to survive in hot water.

Beavers are known to tinker with hydrology too (SN: 7/27/18). They build dams, ponds and wetlands, deepening streams for their burrows and lodges (complete with underwater entrances). The dams slow the water, storing it upstream for longer, and cool it as it flows through the ground underneath.

From 2014 to 2016, aquatic ecologist Benjamin Dittbrenner and colleagues relocated 69 beavers (Castor canadensis) from lowland areas of the state to 13 upstream sites in the Skykomish River basin, some with relic beaver ponds and others untouched. As beavers are family-oriented, the team moved whole clans to increase the chances that they would stay put.

The researchers also matched singletons up with potential mates, which seemed to work well: “They were not picky at all,” says Dittbrenner, of Northeastern University in Boston. Fresh logs and wood cuttings got the beavers started in their new neighborhoods.

At the five sites that saw long-term construction, beavers built 14 dams. Thanks to those dams, the volume of surface water — streams, ponds, wetlands — increased to about 20 times that of streams with no new beaver activity. Meanwhile below ground, wells at three sites showed that after dam construction the amount of groundwater grew to more than twice that was stored on the surface in ponds. Stream temperatures downstream of the dams fell by 2.3 degrees C on average, while streams not subject to the beavers’ tinkering warmed by 0.8 degrees C. These changes all came within the first year after relocation.

“We’re achieving restoration objectives almost instantly, which is really cool,” Dittbrenner says.

Crucially, the dams lowered temperatures enough to almost completely take the streams out of the harmful range for salmon during a particularly hot summer. “These fish are also experiencing heat waves within the water system, and the beavers are protecting them from it,” Fairfax says. “That to me was huge.”

The study also found that small, shallow abandoned beaver ponds were actually warming streams, perhaps because the cooling system had broken down over time. Targeting these ponds as potential relocation sites could be the most effective way to bring temperatures down, the researchers say.  When relocated populations establish and breed, young beavers leaving their homes could seek those abandoned spots out first, Dittbrenner says, as it uses less energy than starting from scratch. “If they find a relic pond, it’s game on.”      More

In the cold, dark depths of the Arctic Ocean, a feast of the dead is under way.

A vast community of sponges, the densest group of these animals found in the Arctic, is consuming the remains of an ancient ecosystem to survive, researchers report February 8 in Nature Communications.

The study highlights just how opportunistic sponges are, says Jasper de Goeij, a deep-sea ecologist at the University of Amsterdam not involved with this work. Evolutionarily speaking, sponges “are more than 600 million years old, and they inhabit all parts of our globe,” he says. Scientists might not know about all of them because many places that sponges inhabit are really difficult to get to, he adds.

Sponges are predominantly filter feeders, and are crucial to nutrient recycling throughout the oceans. The existence of this colony, discovered by a research ship in 2016, however, has been an enigma.

The sponges, which include the species Geodia parva, G. hentscheli and Stelletta rhaphidiophora, live between 700 and 1,000 meters down in the central Arctic Ocean, where there are virtually no currents to provide food, and sea ice covers the water year-round. What’s more, sponges are largely immobile, yet in 2021 researchers, including Teresa Morganti, a marine biologist at the Max Planck Institute for Marine Microbiology in Bremen, Germany, reported that these ones slowly move, using their spicules — microscopic skeletal structures — and leaving them as thick brown trails in their wake.

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In the new study, Morganti and colleagues turned their attention to the matted layer underneath the sponge colony, a smorgasbord of discarded spicules and blackened fossilized life, including empty worm tubes and mollusk shells. To see if this thick mat was a food source, the team analyzed samples of the sponges, the mat material and the surrounding water. The researchers also investigated the genetic makeup of the microbes that live within the sponge tissues, and those in the sediment.

Carbon and nitrogen isotopes — atoms with different numbers of neutrons — in the sponge tissues closely matched those of the dead matter below, suggesting the animals were consuming it. The genetic signature of the microbes showed they had enzymes capable of breaking down the material and were likely dissolving the dead organic matter into food for the sponges (SN: 12/27/13).

The matted layer is up to 15 centimeters thick in places, the researchers found. Assuming that the layer is, on average, greater than 4 centimeters thick, it could provide almost five times the carbon that the sponges would need to survive, the team calculates.

The discovery that the sponges are feeding from below means they are likely moving to access more food, Morganti and colleagues suggest. The scientists also found many sponges to be budding, or breaking off parts to form new individuals, showing active reproduction.

Radiocarbon dating showed the adult sponges — spread across more than 15 square kilometers on the peaks of an underwater volcanic mountain range — to be over 300 years old on average, a “truly outstanding” finding, says Paco Cardenas, a sponge expert at Uppsala University in Sweden who was not involved with the new study. “We expected sponges to grow very slowly, but this had never been measured in the deep sea,” he says.          

The dead ecosystem below the sponges is around 2,000 to 3,000 years older, a once-thriving community of animals that lived in the nutrient-rich conditions created when the volcanoes were last active, the researchers suggest.

Sponges often appear to take advantage of the most abundant carbon sources, which may change as global warming alters the composition of the oceans, says ecologist Stephanie Archer of the ​​Louisiana Universities Marine Consortium in Chauvin, who was not involved in the work. “One big question will be how flexible sponge-microbe associations are, and how quickly they change to take advantage of shifting carbon sources,” she says. More

Hurricane Lizards and Plastic SquidThor HansonBasic Books, $28

As a conservation biologist, Thor Hanson has seen firsthand the effects of climate change on plants and animals in the wild: the green macaws of Central America migrating along with their food sources, the brown bears of Alaska fattening up on early-ripening berry crops, the conifers of New England seeking refuge from vanishing habitats. And as an engaging author who has celebrated the wonders of nature in books about feathers, seeds, forests and bees (SN: 7/21/18, p. 28), he’s an ideal guide to a topic that might otherwise send readers down a well of despair.

Hanson does not despair in his latest book, Hurricane Lizards and Plastic Squid. Though he outlines the many ways that global warming is changing life on our planet, his tone is not one of hand-wringing. Instead, Hanson invites the reader into the stories of particular people, places and creatures of all sorts. He draws these tales from his own experiences and those of other scientists, combining reporting with narrative tales of species that serve as examples of broader trends in the natural world.

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A trip to La Selva Biological Station in Costa Rica, for example, has Hanson reliving the experience of tropical ecologist and climatologist Leslie Holdridge, who founded the research station in the 1950s and described, among other things, how climate creates different habitats, or life zones, as elevation increases. As Hanson sweats his way up a tropical mountainside so he can witness a shift in life zones, he notes, “I had to earn every foot of elevation gain the hard way.” I could almost feel the heat that he describes as “a steaming towel draped over my head.” His vivid descriptions bring home the reason why so many species have now been documented moving upslope to cooler climes.

Hanson doesn’t waste much breath trying to convince doubters of the reality of climate change, instead showing by example after example how it is already playing out. The book moves quickly from the basic science of climate change to the challenges and opportunities that species face — from shifts in seasonal timing to ocean acidification — and the ways that species are responding.

As Hanson notes, the acronym MAD, for “move, adapt or die,” is often used to describe species’ options for responding. But that pithy phrase doesn’t capture the complexity of the situation. For instance, one of his titular characters, a lizard slammed by back-to-back Caribbean hurricanes in 2017, illustrates a different response. Instead of individual lizards adjusting, or adapting, to increasingly stormy conditions, the species evolved through natural selection. Biologists monitoring the lizards on two islands noticed that after the hurricanes, the lizard populations had longer front legs, shorter back legs and grippier toe pads on average than they had before. An experiment with a leaf blower showed that these traits help the lizards cling to branches better — survival of the fittest in action.

In the end, the outcomes for species will probably be as varied as their circumstances. Some organisms have already moved, adapted or died as a result of the warming, and many more will face challenges from changes that are yet to come. But Hanson hasn’t given up hope. When it comes to preventing the worst-case scenarios, he quotes ecologist Gordon Orians, who is in the seventh decade of a career witnessing environmental change. When asked what a concerned citizen should do to combat climate change, he responded succinctly: “Everything you can.” And as Hanson points out, this is exactly how plants and animals are responding to climate change: by doing everything they can. The challenge feels overwhelming, and as a single concerned citizen, much feels out of my hands. Yet Hanson’s words did inspire me to take a cue from the rest of the species on this warming world to do what I can.

Buy Hurricane Lizards and Plastic Squid from Bookshop.org. Science News is a Bookshop.org affiliate and will earn a commission on purchases made from links in this article. More

In a remote corner of Brazil’s Amazon rainforest, researchers have spent decades catching and measuring birds in a large swath of forest unmarred by roads or deforestation. An exemplar of the Amazon’s dazzling diversity, the experimental plot was to act as a baseline that would reveal how habitat fragmentation, from logging or roads, can hollow out rainforests’ wild menagerie.

But in this pristine pocket of wilderness, a more subtle shift is happening: The birds are shrinking.

Over 40 years, dozens of Amazonian bird species have declined in mass. Many species have lost nearly 2 percent of their average body weight each decade, researchers report November 12 in Science Advances. What’s more, some species have grown longer wings. The changes coincide with a hotter, more variable climate, which could put a premium on leaner, more efficient bodies that help birds stay cool, the researchers say.

“Climate change isn’t something of the future. It’s happening now and has been happening and has effects we haven’t thought of,” says Ben Winger, an ornithologist at the University of Michigan in Ann Arbor who wasn’t involved in the research but has documented similar shrinkage in migratory birds. Seeing the same patterns in so many bird species across widely different contexts “speaks to a more universal phenomenon,” he says.

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Biologists have long linked body size and temperature. In colder climates, it pays to be big because having a smaller surface area relative to one’s volume reduces heat loss through the skin and keeps the body warmer. As the climate warms, “you’d expect shrinking body sizes to help organisms off-load heat better,” says Vitek Jirinec, an ecologist at the Integral Ecology Research Center in Blue Lake, Calif. 

Many species of North American migratory birds are getting smaller, Winger and colleagues reported in 2020 in Ecology Letters. Climate change is the likely culprit, Winger says, but since migrators experience a wide range of conditions while globe-trotting, other factors such as degraded habitats that birds may encounter can’t be ruled out.

To see if birds that stay put have also been shrinking, Jirinec and colleagues analyzed data on nonmigratory birds collected from 1979 to 2019 in an intact region of the Amazon that spans 43 kilometers. The dataset includes measurements such as mass and wing length taken from 1979 to 2019 for over 11,000 individual birds of 77 species. The researchers also examined climate data for the region.

By taking careful measurements of tropical birds, such as this white-crowned manakin (Pseudopipra pipra), researchers tracked shifts in body size over 40 years.Cameron Rutt

All species declined in mass over this period, the researchers found, including birds as different as the Rufous-capped antthrush (Formicarius colma), which snatches insects off the forest floor, and the Amazonian motmot (Momotus momota), which scarfs down fruit up in trees. Species lost from about 0.1 percent to nearly 2 percent of their average body weight each decade. The motmot, for example, shrunk from 133 grams to about 127 grams over the study period.

These changes coincided with an overall increase in the average temperature of 1 degree Celsius in the wet season and 1.65 degrees C in the dry season. Temperature and precipitation also became more variable over the time period, and these short-term fluctuations, such as an especially hot or dry season, better explained the size trends than the steady increase in temperature.

“The dry season is really stressful for birds,” Jirinec says. Birds’ mass decreased the most in the year or two after especially hot and dry spells, which tracks with the idea that birds are getting smaller to deal with heat stress.

Other factors, like decreased food availability, could also lead to smaller sizes. But since birds with widely different diets all declined in mass, a more pervasive force like climate change is the likely cause, Jirinec says.

Wing length also grew for 61 species, with a maximum increase of about 1 percent per decade. Jirinec thinks that longer wings make for more efficient, and thus cooler, fliers. For instance, a fighter jet, with its heavy body and compact wings, takes enormous power to maneuver. A light and long-winged glider, by contrast, can cruise along much more efficiently.

“Longer wings may be helping [birds] fly more efficiently and produce less metabolic heat,” which can be beneficial in hotter conditions, he says. “But that’s just a hypothesis.” This body change was most pronounced in birds that spend their time higher up in the canopy, where conditions are hotter and drier than the forest floor.

Whether these changes in shape and size represent an evolutionary adaptation to climate change, or simply a physiological response to warmer temperatures, remains unclear (SN: 5/8/20). Whichever is the case, Jirinec suggests that the change shows the pernicious power of human activity (SN: 10/26/21).

“The Amazon rainforest is mysterious, remote and teeming with biodiversity,” he says. “This study suggests that even in places like this, far removed from civilization, you can see signatures of climate change.” More

A Venus’s-flower-basket isn’t all show. This stunning deep-sea sponge can also alter the flow of seawater in surprising ways.

A lacy, barrel-shaped chamber forms the sponge’s glassy skeleton. Flow simulations reveal how this intricate structure alters the way water moves around and through the sponge, helping it endure unforgiving ocean currents and perhaps feed and reproduce, researchers report online July 21 in Nature.

Previous studies have found that the gridlike construction of a Venus’s-flower-basket (Euplectella aspergillum) is strong and flexible. “But no one has ever tried to see if these beautiful structures have fluid-dynamic properties,” says mechanical engineer Giacomo Falcucci of Tor Vergata University of Rome.

Harnessing supercomputers, Falcucci and colleagues simulated how water flows around and through the sponge’s body, with and without different skeletal components such as the sponge’s myriad pores. If the sponge were a solid cylinder, water flowing past would form a turbulent wake immediately downstream that could jostle the creature, Falcucci says. Instead water flows through and around the highly porous Venus’s-flower-basket and forms a gentle zone of water that flanks the sponge and displaces turbulence downstream, the team found. That way, the sponge’s body endures less stress.

Ridges that spiral around the outside of the sponge’s skeleton also somehow cause water to slow and swirl inside the structure, the simulations showed. As a result, food and reproductive cells that drift into the sponge would become trapped for up to twice as long as in the same sponge without ridges. That lingering could help the filter feeders catch more plankton. And because Venus’s-flower-baskets can reproduce sexually, it could also enhance the chances that free-floating sperm encounter eggs, the researchers say.

It’s amazing that such beauty could be so functional, Falcucci says. The sponge’s flow-altering abilities, he says, might help inspire taller, more wind-resistant skyscrapers.

This simulation shows how water flows around and through a Venus’s-flower-basket (gray). Ridges that spiral across the outside of the sponge cause water inside to somehow slow and swirl, forming particle-trapping vortices. And the sponge’s shape creates a gentle zone of slower water that forms immediately downstream, buffering the creature against turbulence. Vertical cross sections contrast the flow activity of the calm zone (nearer the sponge) and the turbulent zone (downstream).G. Falcucci et al/Nature 2021 More