Cellana dira

The largest mass extinction in Earth's history marked the end of the Permian period, some 252 million years ago. Over 80 percent of all species around at the time disappeared forever from the fossil record. This changed the nature of life on <a href="https://www.earth.com/news/first-fruit-eating-animal-in-earths-history-identified/">Earth</a> and ushered in a new era in which the reptiles evolved and proliferated. In the past, biologists have understood that this rapid radiation of reptiles was driven by the plethora of ecological niches made available by the extinction of Permian species, but new research has now proposed that climate change was also a significant factor behind the spectacular evolution and expansion of reptiles at this time.&nbsp;



“We found that these periods of rapid evolution of reptiles were intimately connected to increasing temperatures. Some groups changed really fast and some less fast, but nearly all reptiles were evolving much faster than they ever had before,” said lead author Tiago R Simões, postdoctoral fellow at the Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, <a href="https://www.harvard.edu/">Harvard University</a>.



For the investigation, Simões and senior author Professor Stephanie E. Pierce (also from Harvard) worked alongside collaborators Professor Michael Caldwell (University of Alberta, Canada) and Dr. Christian Kammerer (North Carolina Museum of Natural Sciences) to examine early amniotes. These animals represent the forerunners of all modern mammals, reptiles, birds, and their closest extinct relatives, at the initial phase of their evolution. At this point in time, the first groups of reptiles and mammal ancestors were splitting from each other and evolving along their own separate evolutionary paths.



“Reptiles represent an ideal and rare terrestrial system to study this question as they have a relatively good fossil record and survived a series of climatic crises including the ones leading up to the largest extinction in the history of complex life, the Permian-Triassic mass extinction,” said Simões.



During the Permian period, it was the synapsids that dominated the vertebrate fauna. These were not reptiles, but the ancestors of mammals, known as stem mammals or proto-mammals. Most of them perished during the end Permian extinction, their ecological niches being taken over by reptiles, including numerous dinosaur species, that evolved and radiated rapidly during the Triassic Period (252-200 million years ago).



The new study, published in the journal <a href="https://www.science.org/journal/sciadv">Science Advances</a>, makes use of morphological data from more than 1,000 fossil specimens from 125 species of reptiles, synapsids, and their closest relatives during approximately 140 million years before and after the Permian-Triassic extinction. This data set is 40 percent larger than the previous largest data set and most of the measurements were made by direct observations and micro-CT scans.&nbsp;



The researchers analyzed this data to identify when these fossil species first originated and how fast they were evolving, using state-of-the-art analytical techniques such as Bayesian evolutionary analysis, which is also used to understand the evolution of viruses such as SARS-COVID 19. They then combined the morphological data with information on body size and with global temperature data that spanned millions of years in the geological record, to provide a broad overview of the animals’ major adaptive responses towards climatic shifts.



The experts found that the appearance of new species, increases in the rates of morphological change and alterations in geographical distributions corresponded to periods of rapidly changing climatic conditions, including global warming and cooling,



“Our results reveal that periods of fast climatic shifts and global warming are associated with exceptionally high rates of anatomical change in most groups of reptiles as they adapted to new environmental conditions, and this process started long before the Permian-Triassic extinction, since at least 270 million years ago, indicating that the diversification of reptile body plans was not triggered by the P-T extinction event as previously thought, but in fact started tens of million years before that," said Professor Pierce.



“One reptile lineage, the lepidosaurs, which gave rise to the first lizards and tuataras, veered in the opposite direction of most reptile groups and underwent a phase of very slow rates of change to their overall anatomy,” said Simões, “essentially, their body plans were constrained by natural selection, instead of going rogue and radically changing like most other reptiles at the time.” The researchers suggest this is due to pre-adaptations on their body size to cope better with high temperatures.



“The physiology of organisms is really dependent on their body size. Small-bodied reptiles can better exchange heat with their surrounding environment. The first lizards and tuataras were much smaller than other groups of reptiles, not that different from their modern relatives, and so they were better adapted to cope with drastic temperature changes. The much larger ancestors of crocodiles, turtles, and dinosaurs could not lose heat as easily and had to quickly change their bodies in order to adapt to the new environmental conditions.”



According to Professor Pierce, large-sized reptiles basically took two routes to deal with these climate shifts - they either migrated closer to temperate regions or invaded the aquatic world where they didn’t need to worry about overheating because water can absorb heat and maintain its temperature much better than air.



“This strong association between rising temperatures in the geological past and a biological response by dramatically different groups of reptiles suggests climate change was a key factor in explaining the origin and the explosion of new reptile body plans during the latest Permian and Triassic,” said Simões.



“We show that the origin and phenotypic radiation of reptiles was not solely driven by ecological opportunity following the end-Permian extinction, as previously thought, but was also the result of multiple adaptive responses to climatic shifts spanning 57 million years," concluded the study authors.&nbsp;



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By <a href="mailto:bosman@truewan.co.za">Alison Bosman</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer

Past climate change drove the rapid evolution of reptiles

The largest mass extinction in Earth's history marked the end...

Small mammals will have a hard time surviving the stressors associated with climate change, according to a new study from the <a href="https://www.sdu.dk/en">University of Southern Denmark</a>. The experts found that large, long-lived animals are better able to cope with extreme weather such as prolonged <a href="https://www.earth.com/news/europe-is-experiencing-its-worst-drought-in-500-years/">drought</a> and heavy rainfall.



The researchers analyzed historical population fluctuations among 157 mammal species from around the world. These fluctuations were compared with weather and climate data from the same time period.&nbsp;



The results are providing new insight into how animals respond to extreme weather. In particular, the experts have identified which animal populations will be the hardest hit by climate change.



"We can see a clear pattern: Animals that live a long time and have few offspring are less vulnerable when extreme weather hits than animals that live for a short time and have many offspring," said study co-author Professor Owen Jones.



Large animals that live longer can cope better with an extreme event such as a persistent drought because these animals have the option to wait until conditions improve to reproduce. The same weather event would affect small mammals differently, as food sources like insects, flowers, and fruits would disappear quickly.&nbsp;



On the other hand, populations of small mammals may also take advantage when weather conditions improve by producing many offspring.



"These small mammals react quickly to extreme weather, and it goes both ways. Their vulnerability to extreme weather should therefore not be equated with a risk of extinction," said study co-author John Jackson.&nbsp;



Some of the animals that will be the most affected by climate change include: Azara's grass mouse, olive grass mouse, elegant fat-tailed mouse opossum, Canadian lemming, Tundra vole, Arctic fox, and the common shrew.



Meanwhile, larger-bodied animals such as African elephants, Siberian tigers, chimpanzees, greater horseshoe bats, llamas, and grizzly bears will be less impacted by extreme weather conditions.&nbsp;



According to the researchers, the results of the study may help experts make predictions about animals they do not know much about.&nbsp;



"We expect climate change to bring more extreme weather in the future. Animals will need to cope with this extreme weather as they always have. So, our analysis helps predict how different animal species might respond to future climate change based on their general characteristics – even if we have limited data on their populations," said Professor Jones.



Jackson emphasized that the ability of an animal species to withstand climate change is not the only factor to consider when assessing the species’ vulnerability to extinction:



"Habitat destruction, poaching, pollution and invasive species are factors that threaten many animal species - in many cases even more than climate change," said Jackson.&nbsp;



The study is published in the journal <a href="https://elifesciences.org/">eLife</a>.



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By <a href="http://csexton@earth.com">Chrissy Sexton</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer

Which animals are most affected by extreme weather?

Small mammals will have a hard time surviving the stressors...

A humble shrimp is raising an alarm about climate change. A study published in the journal <a href="https://www.frontiersin.org/articles/10.3389/fmars.2022.960881/full?&amp;utm_source=Email_to_authors_&amp;utm_medium=Email&amp;utm_content=T1_11.5e1_author&amp;utm_campaign=Email_publication&amp;field=&amp;journalName=Frontiers_in_Marine_Science&amp;id=960881">Frontiers in Marine Science</a> has verified <a href="https://www.whoi.edu/press-room/news-release/warming-oceans-are-getting-louder/">previous observations</a> that two species of snapping shrimp snap louder and more frequently in warmer water.&nbsp;



Scientists from <a href="https://www.whoi.edu/">Woods Hole Oceanographic Institution</a> (WHOI), Ashlee Lillis and T. Aran Mooney, were able to draw a clear connection between warming and snapping by analyzing shrimp off the coast of North Carolina.&nbsp;



The researchers observed that for every one degree (C) increase in water temperature, the shrimp snapped one to two decibels higher and increased in frequency by 15 to 60 percent. The researchers also discovered that the frequency of snaps more than doubled when the water was between 68 and 86 degrees Fahrenheit.



This behavior change is important because these tiny shrimp have a tremendous influence on the environment. Whales and dolphins use their sounds to navigate coastal areas, and the snapping attracts fish, shellfish, and coral larvae to good settling areas.



"These shrimp are the most ubiquitous sound producer in the ocean, and now we have evidence that temperature has a huge impact on their behavior and the overall soundscape," said Lillis, principal scientist at Sound Ocean Science. "That's relevant to everything from migrating whales to larvae trying to use the soundscape, or humans who use the sea for extractive or military purposes."



Mooney points out that although it's crucial for functioning ocean systems, crustacean behavior - as it affects the larger ecosystem - is often ignored when considering the consequences of climate change.&nbsp;



The research was conducted during a short-term heatwave, and the study authors stress that there are still many unanswered questions.&nbsp;



"Climate change is impacting the marine soundscape in fundamental ways," Mooney said. "Warming waters can influence how animals are physically able to communicate and use sound to reproduce and attract mates. We don't yet know what happens to the ecosystem when background noise levels are higher, but there are far-reaching implications."



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By <a href="mailto:nire518@gmail.com">Erin Moody </a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer

Snapping shrimp are getting louder as the ocean warms

A humble shrimp is raising an alarm about climate change....

The mountains of the Philippines are a biodiversity hotspot - home to more unique species of mammals than anywhere else on Earth. Filipino biologist Danilo Balete has spent most of his adult life doing fieldwork and recording the fascinating diversity of living creatures in these mountains. One of the mice he discovered has recently been revealed to belong not only to a new species, but to a whole new genus of rodents.&nbsp;



Larry Heaney, curator of mammals at Chicago’s <a href="https://www.fieldmuseum.org/">Field Museum</a> is the senior author of a paper describing the new mouse.in the&nbsp;<a href="https://academic.oup.com/jmammal">Journal of Mammalogy</a>. “In the past several decades, we’ve learned just how incredibly important the Philippines are in terms of being home to mammals that are found nowhere else," said Heaney, "and a lot of that knowledge can be traced back to fieldwork led by Danny Balete."



Before his untimely death in 2017, Danny Balete’s research overturned previously held notions that biodiversity decreases in mountainous regions because of their harsh environmental conditions. Instead, he proposed that mountainous environments could generate, rather than suppress, species diversity. The mountains of the Philippines are cooler and much wetter than surrounding lowlands, so they become like islands, isolated within the lowland environment below.&nbsp;



Fauna and flora on these “sky islands” tend to evolve separately from each other, meaning that each mountain or mountain range may end up with new and unique species. “The taller and the bigger the mountain range, the more species of mammals will be living there that don't live anywhere else in the world,” said Heaney, who has been studying the mammals of the Philippines for 40 years. He first met Danny Balete in the late 1980s, shortly after Danny completed his Bachelor’s degree at the University of the Philippines.



"I was establishing a research program, and asked around, ‘Who would be a really good, enthusiastic young person to take into the field?’ And several people immediately said, ‘Danny Balete.’ So I invited him to do some field work with me, and he did fantastically well,” recalls Heaney. “He was just a superb field biologist. Danny could identify every plant, every frog, every bug, everything that you encountered, it was just astounding.”



“Danny contributed hugely to scientific knowledge about biological diversity in the Philippines. His enjoyment of biodiversity was really infectious, making him a mentor and inspiration to a generation of researchers and conservationists,” said study co-author Professor Mariano Roy Duya.."By the time of his death, at far too young an age, he was already one of the most prominent biodiversity scientists working in the Philippines.”



In 2007 and 2010, Balete went on expeditions to Mount Kampalili on the island of Mindanao as part of a Field Museum collaboration with the Philippine Eagle Foundation. They wanted to know what mammals lived alongside one of the largest and most critically endangered birds, the Philippine Eagle, and Danny was the perfect person to take along. While on Mount Kampalili, he and the team made a startling discovery: a dark brown mouse with small eyes and a long, tapering nose like a shrew. The creature was different from anything he’d ever seen on that island and looked more like mice he’d seen before, hundreds of miles away, on the island of Luzon.



“High up in the mountains, Danny was able to get cell phone service, so he sent me a text message right away, saying, ‘We just caught this animal that looks a lot like the ones from Luzon and it shouldn’t be here,’” recalls Heaney. “So he immediately recognized that this was something really cool.”



DNA analysis was conducted on three specimens of the new mouse by Dakota Rowsey, the study’s first author, vertebrate collections manager at Arizona State University, and research associate at the Field Museum. The results confirmed that the rodent was different from any known to science, to the extent that it represents a brand new genus of mice. The researchers decided to name the new species Baletemys kampalili, in honor of their departed colleague.&nbsp;



“That DNA study demonstrated that the new mouse was not related to the species up in the northern Philippines, but instead was related to species from Mindanao.&nbsp; It appears to be a remarkable case of what biologists call convergence – distantly related species that have independently evolved to resemble each other in ways that allow them to use habitats and resources in similar ways,” said Rowsey.



“Naming a new species after anyone is a big deal, a major honor given to people who make long-term, high-impact contributions to biodiversity science. Naming a new genus after someone is one of the highest honors biologists can bestow.”



It is not uncommon to discover new species, but a whole new genus is something special. “New species of mammals are being discovered globally at a considerable clip, maybe 50 to 100 new species per year,” said Heaney. “Finding a brand-new genus, previously unknown to science like this one, that only happens at most a couple of times per year. In our 40 years of intensive study of Philippine mammals, this is one of nearly 50 new species, but just the fourth new genus we discovered.”



The new genus’s scientific name means “Balete’s mouse,” in honor of Balete’s work in discovering it and so many other creatures. “As we began picking up the pieces after his death, it became obvious to us that we had to name this new mouse after him; he deserves this,” said Professor Duya.



In addition to honoring Balete, the researchers say the new genus is important because it’s another puzzle piece in understanding the diversity of life in the Philippines. Demonstrating that Mount Kampalili is home to a mouse found nowhere else on Earth may bolster conservation efforts by Indigenous communities which would help the mouse’s neighbors, including the critically endangered Philippine Eagles.



“It’s really important to show that when we protect one species, like the magnificent Philippine Eagle, we protect not only our unique biological wealth but our cultural heritage as well,” said study co-author Jayson Ibanez of the Philippine Eagle Foundation.



The Philippine eagle and the new “Balete’s mouse” are neighbors to the Indigenous Mandaya group&nbsp;of Mount Kampalili. “Indigenous peoples get very excited whenever they learn that they share their homeland with a totally unique lifeform. And in this case, when we help protect Mount Kampalili, we also protect the primary watershed, airsheds, and biocultural sanctuaries for much of southeastern Mindanao, giving huge benefits to all the people who live here,” said Ibanez. “With all of the threats from watershed destruction and climate change, we need all the help we can get.”



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By <a href="mailto:bosman@truewan.co.za">Alison Bosman</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer

Shrew-like mouse will help protect Phillipine eagles

The mountains of the Philippines are a biodiversity hotspot -...

Frogs have evolved a wide variety of strategies to evade <a href="https://www.earth.com/news/some-bats-buzz-like-hornets-to-deter-predators/">predators</a>. Some of the defense mechanisms used by frogs are quite bizarre, such as playing dead, screaming, urinating, or puffing up their bodies.&nbsp;



In a new study led by evolutionary biologist Stefan Lüpold at the <a href="https://www.uzh.ch/en.html">University of Zurich</a>, researchers set out to investigate how frogs choose between two specific antipredator strategies: fleeing the scene versus avoiding detection through camouflage. The results suggest that frogs evolved to have either small or large brains depending on which of these defense strategies they use.&nbsp;



Despite their effectiveness, both fleeing and camouflaging come with potential costs. For example, it takes a lot of energy to physically escape a predator. But while camouflage may save energy, it can be detrimental to mating success and greatly limits where animals can safely live.&nbsp;



The study was focused on antipredator adaptations in 102 Chinese frog species. The analysis revealed that frogs with fewer predators had adapted bodies for escaping, including large brains and muscular hind legs.&nbsp;



On the other hand, when frogs are faced with many predators, fleeing is no longer the best option. “Under these unfavorable conditions, the cognitive costs needed for this strategy outweigh its benefits,” explained Lüpold. “Here, evolution has led to a gradual shift from cognitive predator evasion to camouflage – and thus smaller brains.”



According to the researchers, the study is the first to establish a direct link between brain evolution and different strategies for evading predators.



“Our study highlights that research on brain evolution has to consider metabolic costs as much as it focuses on cognitive benefits,” said Lüpold.&nbsp;



"Specifically, our phylogenetic path analysis reveals an indirect relationship between predation risk and crypsis that is mediated by brain size," wrote the study authors. "This result suggests that at a low predation risk, frogs can afford to be conspicuous and use their large brain for cognitive predator evasion. This strategy may become less efficient or energetically costlier under higher predation pressure, favoring smaller brains and instead increasing crypsis."



The study is published in the journal <a href="https://www.science.org/journal/sciadv">Science Advances</a>.



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By <a href="http://csexton@earth.com">Chrissy Sexton</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer

Conspicuous frogs have big brains to evade predators

Frogs have evolved a wide variety of strategies to evade...

According to the World Health Organization, mosquitos are the deadliest animals on Earth. The <a href="https://www.earth.com/news/climate-change-heightens-risk-of-most-infectious-diseases/">diseases</a> they pass on to humans, including malaria, Zika, West Nile, Chikungunya and dengue, are responsible for around 725,000 deaths each year. The insects use olfactory cues to locate humans with an unerring accuracy, preferring to bloodfeed on humans over other animals, and so the means by which they detect human presence has become the object of scientific investigation.&nbsp;&nbsp;



More than a decade ago, Leslie Vosshall, a <a href="https://www.hhmi.org/">Howard Hughes Medical Institute</a> (HHMI) Investigator, turned her attention to understanding the mosquito olfactory system in a quest to find ways to blunt the insect’s uncanny ability to locate human prey. “I wanted to do something the public could be excited about,” she says. And her new work would indeed prove to have a major impact – just not what she’d anticipated. Vosshall describes the results as “a huge, staggering surprise."



Mosquitos detect chemical signals using odor receptors that are located on nerve cells (neurons) found on the antennae and some of the mouth parts. The accepted understanding, based on the Nobel Prize-winning research on mice by Linda Buck (now at Fred Hutchinson Cancer Center) and Richard Axel at Columbia, was that the smell sensing systems in animals are exquisitely specialized and organized. Each olfactory neuron has just one type of receptor, which detects a specific odor and then connects to just one structure (called a glomerulus) in the olfactory bulb of the brain.&nbsp;



According to this paradigm, a mosquito would be expected to have separate neurons that detect the smell of human body odor, and the presence of exhaled carbon dioxide (CO2), and it might be a straightforward process to disable these particular neurons and render mosquitos insensitive to human cues. Or that’s what the researchers thought. “We as a field were so influenced by Buck and Axel,” says Vosshall (who was a postdoc student in Axel’s lab). “Those were the rules.”



Initially, the researchers analyzed the DNA in the complete genome of a blood-sucking mosquito, something that had not yet been undertaken. “No one had done genome editing before in part because the genome was so fragmented,” Vosshall explains. Then, Meg Younger a former postdoc in the lab set out to try to answer a puzzling question. Mosquitoes are attracted to both the CO2 that people breathe out and to human body odor.&nbsp;



“But there’s something magical about adding those two ingredients together, where one plus one equals twenty,” she says. When both olfactory cues are present together, the insects become very excited and focused, and they start to hunt for humans ferociously. It is as though the two stimuli become amplified somehow in the olfactory system.&nbsp;



In order to understand what was happening, Younger tried to identify which olfactory neurons responded to CO2 and which to body odor, and then to trace the pathways of the signals to the brain. She used the gene editing tool CRISPR to slip a fluorescent marker protein into the neurons that had receptors for CO2 and another marker into those that could sense chemicals from body odor. That’s when the research took an unexpected turn. “It was like Alice in Wonderland – where nothing makes sense,” Vosshall says.



The results, published in the journal <a href="https://linkinghub.elsevier.com/retrieve/pii/S0092867422009278">Cell</a>, show something altogether new in the world of olfactory systems. The fluorescent receptor genes indicated that individual neurons did not only carry receptors for one chemical cue, as was previously thought. Instead, the neurons were chock full of multiple different types of receptors. We found that “all the Buck and Axel rules were thrown in the garbage can by mosquitos,” says Vosshall.&nbsp;



The results were so startling that Vosshall’s lab has spent years painstakingly proving that they were actually real, using several additional lines of evidence. For instance, Olivia Goldman, a PhD student in the lab, harnessed a relatively new and revolutionary technique called single nucleus RNA sequencing (snRNA-seq) to probe which genes are turned on in individual neurons. The approach confirmed that each neuronal cell does indeed use many different kinds of receptors.&nbsp;



In addition, the researchers teamed up with scientists at the Swedish University of Agricultural Sciences, who had done ground-breaking research using electrodes inserted into individual olfactory neurons in mosquitos. That method also confirmed that a single mosquito neuron can detect different smells – even two different ‘flavors’ of body odor, a perfumy smell and a stinky foot odor, which require two entirely different classes of receptors.&nbsp;



Those results “were a huge relief,” Vosshall says. She anticipated widespread skepticism to her conclusions, “so the number of levels of evidence that we used to prove it was intense,” she says. In fact, many scientists did challenge these new findings at first. But not only was the supporting evidence overwhelming, similar findings were also emerging from neuroscientist Christopher Potter’s lab at Johns Hopkins University School of Medicine.&nbsp;



Working with both the fruit fly and a mosquito species, Potter’s team published a paper in eLife in April suggesting that “co-expression of chemosensory receptors is common in insect olfactory neurons.” In the past, the conventional wisdom of one receptor per smell and one receptor per neuron was so strong that there was no reason to probe for multiple receptors, says Potter. “Now we know to look for it.”



The findings of Vosshall and her team have overturned the conventional model of the neural circuity animals use to detect, and distinguish between, thousands of distinct smells. “This is a big deal,” says Potter. “It really changes the way we think the insect olfactory system is working.”&nbsp;



The added complexity of the insect olfactory system makes perfect sense in evolutionary terms, as mosquitos must find food in order to survive. The presence of different types of odor receptors on each neuron enhances the insects’ ability to detect exhaled CO2 along with a whole array of body smells. If some receptors were to be blocked, a mosquito would simply use others that remained intact.&nbsp;



“It is a really good trick,” explains Vosshall. “Mosquitoes have Plan B after Plan B after Plan B. To me the system is unbreakable.” That’s obviously not good news for the effort to reduce the toll from mosquito-borne diseases, such as malaria, yellow fever, and dengue, by trying to block receptors. But perhaps an alternative strategy might be to overwhelm the whole system with alternative smells, adds Potter. At least now “we have a more realistic view of what we are up against,” he says.



In the meantime, Vosshall aims to compare the olfactory neurons of blood-dining mosquitoes with those from purely vegetarian mosquito relatives to see if the more extreme receptor complexity is a unique adaptation for those species that only hunt humans. And as for the puzzle Vosshall first started to probe – how the combined sensing of both CO2 and body odor greatly amplifies the message to the brain? One of her former postdocs, Meg Younger, is now tackling the question in her new lab at Boston University.



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By <a href="mailto:bosman@truewan.co.za">Alison Bosman</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer

Mosquitos use unbreakable system to track human blood

According to the World Health Organization, mosquitos are the deadliest...

Australian snubfin (Orcaella heinsohni) and humpback (Sousa sahulensis) <a href="https://www.earth.com/news/dolphins-have-accents-that-vary-by-region/">dolphins</a> co-exist peacefully throughout most of their range, primarily in shallow tropical and subtropical coastal waters from southern New Guinea to northern Australia. A team of researchers led by <a href="https://www.flinders.edu.au/">Flinders University</a> has now set out to investigate why these two species are able to co-exist within this range.&nbsp;



“A major challenge in ecology and conservation is to understand the means by which species coexist as this is the basis of biodiversity,”&nbsp;explained study lead author Guido Parra Vergara, an associate professor of Behavioral Ecology at Flinders. “If we are to understand the effects of global change on marine mammal biodiversity, and how we can maintain assemblages of coexisting species, we need to understand their patterns of co-occurrence; the biological significance of their interactions, and the mechanisms underlying their coexistence.”



According to the “<a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ecological-niche">ecological niche theory</a>,” the coexistence of closely related species is promoted by resource partitioning in space and time. However, understanding how these two specific dolphin species co-exist is rather challenging, due to their size, high mobility, longevity, and the fact that they spent most of their time underwater.



Each of the species is characterized by small populations (usually fewer than 150 individuals) which overlap spatially, have similar patterns of habitat use and behavioral activities, and are often found in mixed species groups. Thus, segregation into exclusive spatial and temporal ranges, and differences in habitat use and behavioral patterns are insufficient to explain their co-existence.



By comparing stable isotope ratios of carbon and nitrogen in their skin – the former providing a quantifiable estimate of habitat and resource use, while the latter offering cues regarding their position in the trophic chain – the scientists found that, although both species feed at similar trophic levels, rely on similar basal food resources, and have substantial dietary overlaps, they are nevertheless characterized by subtle differences in habitat use and prey selection, which may promote their co-existence. More specifically, snubfin dolphins forage on a wider diversity of prey, while humpback dolphins forage in a larger variety of habitats.



“Food diversity and abundance and habitat heterogeneity are key factors promoting the coexistence of these two dolphin species, and pressure from overfishing and pollution that could reduce prey abundance and diversity or deteriorate their habitat quality could affect the future of such dolphin co-existence,”&nbsp;said Professor Parra Vergara.



“Because dolphins play important roles in maintaining the structure and function of marine communities and ecosystems, any pressures on their food and habitat resources need to be considered when planning future multi-species conservation,” he concluded.



The study is published in the journal <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.8937">Ecology and Evolution</a>.&nbsp; &nbsp;



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By <a href="mailto:andrei.ionescu5891@gmail.com">Andrei Ionescu</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer&nbsp;&nbsp;

How two species of dolphins coexist in Australia

Australian snubfin (Orcaella heinsohni) and humpback (Sousa sahulensis) dolphins co-exist...

Cellana dira

Taxonomic tree: