A new study published in the journal Communications Biology has shed light on the earliest stages in the evolution of male-female differentiation and sex chromosomes--and found the genetic origins of the two sexes to be unexpectedly modest.

This is a female Eudorina colony with 32 large egg cells, some of which are pairing with small male sperm cells. On the upper right is a male sperm packet which has found the female colony and is about to release its sperm inside [Credit: Hiroko Kawai-Toyooka, University of Tokyo]

James Umen, Ph.D., member, Enterprise Rent-a-Car Institute for Renewable Fuels and Joseph Varner Distinguished Investigator at the Donald Danforth Plant Science Center was part of a research team led by Dr. Hisayoshi Nozaki at the University of Tokyo who have been investigating the evolution of male and female sexes in a group of freshwater photosynthetic protists called volvocine green algae, a group that is well-known to scientists for capturing early stages in the evolution of sexes and multicellularity. Previous studies in animals and plants identified a general trend of expansion and differentiation between male and female sex chromosomes, often leading to large genetic differences between them; but these studies could not capture the earliest stages of evolution where distinct sperm and egg cell types first evolved from a simpler ancestral mating system with equal-sized gametes, known as isogamy.

The research team focused on two especially informative and closely-related multicellular volvocine species from the genera Yamagishiella and Eudorina which bracket the transition from isogamy to male/female sexes. While 32-celled Yamagishiella and Eudorina colonies look very similar to each other, the former is isogamous while the latter produces small male gametes and large female gametes. The team used high-throughput genome sequencing of the chromosomal regions that specify mating type in Yamagishiella and male-female differentiation in Eudorina, and then compared these regions.

While evolutionary theory predicted an expansion and/or increased genetic complexity of the sex determining region associated with the evolution of sexes in Eudorina, the results of the study showed the opposite, with Eudorina having the most diminutive and genetically least complex sex-determining region found to date found among all volvocine species. In essence, the major difference between males and females in Eudorina could be reduced to the presence or absence of a single gene called MID that resides in a tiny chromosomal region.

"This new study punches a hole in the idea that increased genetic complexity of sex chromosomes accompanied the origin of sexes," said Umen. "Moreover, the work also has practical implications since it expands our understanding of how to identify mating types and sexes in new species of algae that we might want to breed as crops for improved traits relating to biofuel or biotechnology applications."

Source: Donald Danforth Plant Science Center [March 08, 2018]

About 2 to 3 million years ago, a group of spiders let out long silk threads into the wind and set sail, so to speak, across the Pacific Ocean to Hawaii. These spiders were parasites of other spiders, invading their webs, snipping threads to steal insects that had been caught. But there weren't many webs to rob on Hawaii when they arrived. So they expanded their repertoire, looking for other ways to survive by trapping and eating other spiders. A new species evolved from those first spiders, after finding a way to live on rocks. And then another species evolved to live under leaves. And then another. And then 11 more species.

Gold Molokai spider [Credit: George Roderick]

Charles Darwin first noted this phenomenon, called adaptive radiation, in the beaks of finches of the Galapagos Islands. His study of the finches' diversity led to his theory of evolution by natural selection. Yet today, much remains unknown about how adaptive radiation, and thus evolution, actually work. Hawaii is even more of a hotbed for biological diversification than the Galapagos due to its isolation.

In Hawaiian Ariamnes stick spiders, adaptive radiation has resulted in 14 species now living across Hawaii. They share a generally similar body type, but each is a separate species with distinct physical traits. Remarkably, stick spiders with similar traits - yellow and red coloring, for example - live on different Hawaiian islands but aren't each other's closest relatives; they are a rare instance where a physical form has evolved separately on each island, according to a new study by scientists at the University of California, Berkeley. The study shows that evolution has led to a predictable and independently evolved set of similar forms in spiders on each island.

"This very predictable repeated evolution of the same forms is fascinating because it sheds light on how evolution actually happens," said Rosemary Gillespie, professor and Schlinger Chair in Systematic Entomology at UC Berkeley and lead author of the paper. "Such outstanding predictability is rare and is only found in a few other organisms that similarly move around the vegetation."

Ariamnes corniger, a stick spider from East Maui, Hawaiian Archipelago. This white matte ecomorph is cryptic against lichen [Credit: George Roderick]

The study of Ariamnes stick spiders will be published in the journal Current Biology. It was funded by the National Science Foundation and the William M. and Esther G. Schlinger Foundation.

"This study provides insights into a fundamental question about the origins of biodiversity, but also presents a remarkable story that can call attention to the need for conserving nature in all of its forms," said study co-author George Roderick, professor and chair of the Department of Environmental Science Policy and Management at Berkeley.

Hawaii is a chain of islands that formed chronologically, so the scientists were able to study the spiders' adaptive radiations over time as they moved from old to new islands. The oldest island, Kauai, was formed 5 million years ago, followed by Oahu, Molokai, Lanai, Maui and finally the big island of Hawaii, the youngest at less than 1 million years old.

The study found that stick spiders have evolved and differentiated from a single species on the same island. So, spider types on any one island were generally more closely related to very different looking spiders on the same island than to spiders that looked the same on other islands. For instance, a white spider on Oahu is a closer relative to the brown spider on the same island than it is to a white spider on Maui.

An undescribed species of Ariamnes from Kauai, Hawaiian Archipelago. It is an example of the dark ecomorph [Credit: George Roderick]

"You can find these spiders in pretty much every habitat on each island," Gillespie said. "This really detailed and finely tuned repetition of evolution of the same form is really quite uncommon."

The spiders can be grouped into three distinct ecological types, called ecomorphs: A brown one that lives in rocks; a gold one that lives in under leaves, and a white one that's a matte color and lives on lichen.

The analysis of stick spiders mirrors Gillespie's previous discovery in Hawaiian Tetragnatha spiders, another group that shows remarkable adaptive radiation. This group of spiny-legged spiders does not spin a web and has repeatedly evolved similar ecomorphs since its ancestor arrived in Hawaii. That study was featured on the cover of the journal Science in 2004.

The varied habitat types on the Hawaiian Islands, cold and wet areas closely juxtaposed with hot and dry, have provided a rich tapestry of species diversity. The flip side of such extraordinary diversity that evolved in isolation is its vulnerability to change and to invasive species that are now flooding in as a result of human traffic, Gillespie said.

"We need to be able to figure out this diversity and document it and describe what's so special about it, so that people know about it," Gillespie said. "It's being lost and it's a desperate situation."

Source: University of California - Berkeley [March 08, 2018]

New research by University of Alberta cellular biologists is putting into question existing theories about what's responsible for organizing a central part of our cells, known as the Golgi apparatus.

Artist's conception of the Golgi apparatus, showing the hallmark "stacked pancake" appearance. UAlberta research  reveals that this cellular structure is older and more complex than previously thought, which could lead to new insights into cellular diseases [Credit: University of Alberta]

"The Golgi sorts material as it is made and directs it to different locations. It is like a cellular post office. Our research—which goes back in time to examine how cells evolved over billions of years—challenges existing theories around how the cell's Golgi is structured," said Joel Dacks, a U of A cellular biologist and Canada Research Chair in Evolutionary Cell Biology, who led the study.

"This is critical because when this important element of a cell's membrane trafficking system malfunctions in humans, diseases such as Alzheimer's and Parkinson's occur."

The study—conducted in partnership with scientists in the Czech Republic—aims to explain fundamentals of how healthy cells work, which should help in understanding disease when cells go wrong, he noted. "You can't figure out why your car doesn't run if you don't know how cars work in the first place."

Scientists have long postulated that a single gene is responsible for the Golgi apparatus's hallmark stacked membrane look, a collection of flattened membrane-enclosed disks known as cisternae, he explained.

Using new and existing genome sequence data and computational analysis, Lael Barlow, a Ph.D. student and the paper's first author, examined the evolution and prevalence of genes that were thought to be responsible for Golgi stacking across the broadest range of organisms, from amoeba to fish to humans.

"After testing every gene proposed as responsible, we found that none of them match the predicted pattern of presence and absence across genomes as the gene for stacking of the Golgi," said Barlow.

Instead, the authors suggested a previously proposed explanation—many different types of genes, each acting in overlapping and complementary ways, might explain the phenomenon and should be studied a lot more.

"The analogy would be that instead of a great song being the result of a single essential solo artist, with backup singers, the song is the result of a choir and many choristers that can compensate for one another," noted Dacks.

Moreover, their study provided the most detailed picture to date of Golgi organization in our ancient cellular ancestry, showing that it was more complex than previously thought, and importantly, that the separate "pancake" organization had already been set up, more than a billion and half years ago.

"It's very exciting, kind of like replacing old grainy aerial photos of a Mayan settlement with much higher-resolution images of the same site, showing that the society was more complex than anticipated at that time point and how it was organized," said Dacks.

"This work points to a new path to understanding the organization of a critical part of our cells and brings into the light an even more detailed picture of our deep evolutionary history."

The study is published in BMC Biology.

Author: Lesley Young | Source: University of Alberta [March 08, 2018]

Ancient microbes may have been producing oxygen through photosynthesis a billion years earlier than we thought, which means oxygen was available for living organisms very close to the origin of life on earth. In a new article in Heliyon, a researcher from Imperial College London studied the molecular machines responsible for photosynthesis and found the process may have evolved as long as 3.6 billion years ago.

The crystal structure of Photosystem I (PDB ID: 1JB0) [Credit: Elsevier]

The author of the study, Dr. Tanai Cardona, says the research can help to solve the controversy around when organisms started producing oxygen -- something that was vital to the evolution of life on earth. It also suggests that the microorganisms we previously believed to be the first to produce oxygen -- cyanobacteria -- evolved later, and that simpler bacteria produced oxygen first.

"My results mean that the process that sustains almost all life on earth today may have been doing so for a lot longer than we think," said Dr. Cardona. "It may have been that the early availability of oxygen was what allowed microbes to diversify and dominate the world for billions of years. What allowed microbes to escape the cradle where life arose and conquer every corner of this world, more than 3 billion years ago."

Photosynthesis is the process that sustains complex life on earth -- all of the oxygen on our planet comes from photosynthesis. There are two types of photosynthesis: oxygenic and anoxygenic. Oxygenic photosynthesis uses light energy to split water molecules, releasing oxygen, electrons and protons. Anoxygenic photosynthesis use compounds like hydrogen sulfide or minerals like iron or arsenic instead of water, and it does not produce oxygen.

Previously, scientists believed that anoxygenic evolved long before oxygenic photosynthesis, and that the earth's atmosphere contained no oxygen until about 2.4 to 3 billion years ago. However, the new study suggests that the origin of oxygenic photosynthesis may have been as much as a billion years earlier, which means complex life would have been able to evolve earlier too.

A culture of Synechocystis sp. PCC 6803, a type of unicellular Cyanobacteria [Credit: Elsevier]

Dr. Cardona wanted to find out when oxygenic photosynthesis originated. Instead of trying to detect oxygen in ancient rocks, which is what had been done previously, he looked deep inside the molecular machines that carry out photosynthesis -- these are complex enzymes called photosystems. Oxygenic and anoxygenic photosynthesis both use an enzyme called Photosystem I. The core of the enzyme looks different in the two types of photosynthesis, and by studying how long ago the genes evolved to be different, Dr. Cardona could work out when oxidative photosynthesis first occurred.

He found that the differences in the genes may have occurred more than 3.4 billion years ago -- long before oxygen was thought to have first been produced on earth. This is also long before cyanobacteria -- microbes that were thought to be the first organisms to produce oxygen -- existed. This means there must have been predecessors, such as early bacteria, that have since evolved to carry out anoxygenic photosynthesis instead.

"This is the first time that anyone has tried to time the evolution of the photosystems," said Dr. Cardona. "The result hints towards the possibility that oxygenic photosynthesis, the process that have produced all oxygen on earth, actually started at a very early stage in the evolutionary history of life -- it helps solve one of the big controversies in biology today."

One surprising finding was that the evolution of the photosystem was not linear. Photosystems are known to evolve very slowly -- they have done so since cyanobacteria appeared at least 2.4 billion years ago. But when Dr. Cardona used that slow rate of evolution to calculate the origin of photosynthesis, he came up with a date that was older than the earth itself. This means the photosystem must have evolved much faster at the beginning -- something recent research suggests was due to the planet being hotter.

"There is still a lot we don't know about why life is the way it is and how most biological process originated," said Dr. Cardona. "Sometimes our best educated guesses don't even come close to representing what really happened so long ago."

Dr. Cardona hopes his findings may also help scientists who are looking for life on other planets answer some of their biggest questions.

Source: Elsevier [March 06, 2018]

Primitive air-breathing fish, whose direct ancestors first appeared around 400 million years ago, show mechanisms controlling the heart which were previously considered to be found only in mammals -- according to a new study.

This is a South American lungfish, Lepidosiren paradoxa [Credit: Gustavo M. Oda]

Mammals show an increase in heart rate when breathing in and a decrease during expiration -- a cardiorespiratory process known as respiratory sinus arrhythmia (RSA). This process and its underlying control mechanisms have been considered by many scientists to be solely mammalian but the present study questions this assumption.

Scientists in Britain and Brazil studied the South American lungfish, Lepidosiren paradoxa, and discovered that systems enabling this primitive vertebrate to control blood flow during bouts of air-breathing have close similarities to those identified in mammals.

Lungfish are members of an ancient group of lobe-finned fishes (Class Dipnoi), having a continuous fossil record originating in the Devonian period around 400 million years ago. This was a time when the first vertebrates crawled on to land to give rise to amphibians and over succeeding millennia reptiles, birds and mammals.

With their proto-lungs and proto-limbs, lungfish represent the earliest stage in the evolution of air-breathing vertebrates. They inhabit tropical, freshwater pools and slow-flowing rivers, which often contain very low levels of dissolved oxygen and can disappear during the dry season.

The lungfish shares a periodic breathing pattern with the terrestrial vertebrates, rising to the water's surface at regular intervals to ventilate its lung-like air-breathing organ and depending exclusively on these lungs for oxygen uptake during drought.

Led by experts at the University of Birmingham and the Federal University of São Carlos (UFSCar), in São Paulo, the international team published its findings in Science Advances.

Professor Ted Taylor, from the University of Birmingham, said: "When lungfish gulp air at the water's surface, their heart rate instantly increases -- signalling a diversion of blood to the creature's lungs.

"This is possible because the animal has an undivided heart, enabling the proportion of blood diverted to the lungs to be varied; unlike mammals, as we have a completely divided heart with equal volumes of blood pumped separately to lungs and body with each heartbeat.

"Our study established a clear function in lungfish for these increases in heart rate in maximising oxygen uptake during each air breath that has not been definitively demonstrated for RSA in mammals. This suggests that it may be a relic of their link to ancient amphibious ancestors."

Professor Taylor added that "The lungfish has a relatively complex control system which generates these respiration-related changes in heart rate, with properties that anticipate those described for mammals.

"We found that these include multiple locations for nerve cells in the brainstem that innervate the heart with insulated fibres that conduct rapid impulses, causing an instantaneous cardiac response to each air-breath."

This illustration in a fish with a proven ancient lineage of a highly evolved system controlling variations in heart rate suggests that its evolution was necessarily linked to the advent of air breathing over primitive vertebrate lungs rather than the much later appearance of mammals.

This understanding questions assumptions over the primacy of mammals made by some biomedical physiologists and many psychobiologists, demonstrating that "primitive" mechanisms though early are not necessarily simple.

Source: University of Birmingham [March 05, 2018]

Evolutionary biologists have now discovered that the Pygmy Marmoset – the world’s smallest monkey – is not one species but two.

Pygmy Marmoset [Credit: University of Salford]

Weighing just 100 grams - roughly the size of a large tomato - the insect-eating primate was first described scientifically in 1823 by German naturalist Johann Spix as Cebuella pygmaea, with a sub-species subsequently found.

Now a team led by the University of Salford, using the latest techniques in genomics and phylogenetics, have established proof of two clades or branches of pygmy marmosets, that have diverged from one another around 2 – 3 million years ago.

The study was restricted to monkeys in the Brazilian Amazon, but there are indications that researchers may discover more species with further research in the forests of the other countries where they live.

Implications for conservation efforts

Findings like this have serious implications for conservation, since population numbers essentially are halved when a species is suddenly split in two in the light of new scientific evidence.  Luckily for the pygmy marmosets, the forests where they are found are amongst the best preserved patches of Amazon, the scientists say.

The study, led by Jean Boubli, professor of tropical ecology and conservation, at Salford University, UK, and the first ever to use genomics to investigate the evolutionary history of a group of New World primates, is published in Molecular Phylogenics and Evolution.

The team, which included scientists from four Brazilian research institutes and US-based Conservation international, found one of the distinct Pygmy Marmoset species is found in Brazil’s Japurá basin, extending west into Colombia, northern Peru and Ecuador, while the other, is found south of the Amazon River, east to the Madeira River in Brazil, and possibly extending into Peru and Bolivia.

They employed genome sequencing (ddRADseq) to study the evolutionary history of Cebuella and found two lineages.

Keep original name?

Professor Boubli said: “There has long been confusion over the taxonomy of these wonderful creatures mostly because Spix did not record in his travel diaries the exact location where he collected the type of Cebuella pygmaea in the early 1800s.  That creates confusion as to which of  the two recently uncovered species should keep the original name; that of the north or of the south of the Amazon.

“The beauty of genomics means that we can now see the pygmy marmoset is a term for two species which have been evolving independently for nearly 3 million years.”

According to the IUCN Red List of Threatened Species, Pygmy Marmosets are species of “Least Concern.” But recent disease epidemics resulting have prompted the IUCN Species Survival Commission’s Primate Specialist Group to recommend updating that status to Vulnerable.

The team is now collecting more data including faeces from different localities to clarify the taxonomy of Pygmy Marmosets and the geographic ranges of the two species already identified—and possibly even that of new ones.

Source: University of Salford [March 02, 2018]

In a study spanning twelve years, researchers from Kyoto University, and with Ryukoku University have developed a method to calculate the fluctuating stability of a natural ecological community in Maizuru Bay.

Kyoto researchers spend a decade tracking changes in fish communities [Credit: Kyoto University/Reiji Masuda]

Their findings, published in Nature, provide insight into and new methodologies for ecological and population research.

How biological communities are maintained is a big question in ecology. While current studies suggest community stability can be influenced by species diversity and interactions, these ideas have almost never been tested in natural ecosystems.

"Previous research focused on issues such as the birth-death process, like when a predator eats prey, and inside a somewhat controlled environment," explains lead author Masayuki Ushio. "Even then, it is challenging to measure the rapidly changing interactions of multiple species in nature."

A key reason for this is that natural ecosystems do not typically exhibit equilibrium dynamics, and so the most viable way to measure changes is to keep constant records of organisms in a particular location.

Fortunately, Reiji Masuda of the Field Science Education and Research Center has been doing just that in Maizuru Bay. For twelve years, he has been diving into the waters every two weeks, recording the populations of all the fish and jellyfish he encountered.

"I initially started these observations in 2002 to see what organisms lived in the area and how they change over time," Masuda describes. "When I showed my work to Masayuki Ushio and Michio Kondoh at Ryukoku University, they suggested we work together and build a model to chart the interactions between the organisms."

The model was constructed by applying a time series analysis tool -- empirical dynamic modeling, or EDM -- to the Maizuru Bay data set. EDM is designed to analyze the fluctuating dynamics of a natural ecosystem, without setting any defined equations. This was then further developed to analyze the ecosystem's dynamic stability.

What they found was a complex web of interactions, where organisms have positive or negative effects on each other, and more importantly, showed that short-term changes in the network influences overall community dynamics.

"We could even see that things such as diversity, species interactions, and stability itself fluctuate throughout time," says Ushio. "This suggests that these properties are key to understanding the mechanisms underlying the functioning of natural ecosystems."

The team's methods can be readily applied to other fields, from neuroscience, microbiology, to economics.

"This is by far one of the most comprehensive looks at how much an ecosystem can change in the natural world," concludes team leader Michio Kondoh. "I was surprised to see that community stability, which is often assumed to be constant, is in fact changing over time. The robustness of ecological communities depends on timing and seasons."

Source: Kyoto University [March 02, 2018]

For over a century, speciation -- where one species splits into two -- has been a central focus of evolutionary research. But a new study almost 20 years in the making suggests "speciation reversal" - where two distinct lineages hybridize and eventually merge into one -- can also be extremely important. The paper, published in Nature Communications, provides some of the strongest evidence yet of the phenomenon, in two lineages of Common Ravens.

A raven is shown in the rain [Credit: Bjorn Aksel Bjerke/University of Oslo]

"The bottom line is [speciation reversal] is a natural evolutionary process, and it's probably happened in hundreds or almost certainly thousands of lineages all over the planet," said Kevin Omland, professor of biological sciences at University of Maryland, Baltimore County (UMBC) and co-author on the new study. "One of our biggest goals is to just have people aware of this process, so when they see interesting patterns in their data, they won't say, 'That must be a mistake,' or, 'That's too complicated to be correct.'"

"We examined genomic data from hundreds of ravens collected across North America," said Anna Kearns, the study's first author and a former postdoctoral fellow at UMBC, who is now a postdoc at the Smithsonian Center for Conservation Genomics. "Integrating all of the results across so many individuals, and from such diverse datasets, has been one of the most challenging aspects of this study. Next-generation genomic techniques are revealing more and more examples of species with hybrid genomes."

When Omland initially began work on this project in 1999, Common Ravens were considered a single species worldwide. He thought further research might uncover two distinct species -- perhaps an "Old World" and "New World" raven -- but the real story is much more complicated. Omland reported the existence of two Common Raven lineages in 2000, one concentrated in the southwestern United States dubbed "California," and another found everywhere else (including Maine, Alaska, Norway and Russia) called "Holarctic."

A raven is shown perching in the snow [Credit: Bjorn Aksel Bjerke/University of Oslo]

Since then, the plot has thickened. Two undergraduates in Omland's lab, Jin Kim and Hayley Richardson, analyzed mitochondrial DNA from throughout the western United States and found the two lineages are extensively intermixed. In 2012, the Norwegian Research Council provided major funding for the project and Kearns spent a year at the University of Oslo analyzing nuclear genome data.

The best explanation based on the team's analysis is that the California and Holarctic lineages diverged for between one and two million years, but now have come back together and have been hybridizing for at least tens of thousands of years.

"The extensive genetic data reveals one of the best supported examples of speciation reversal of deeply diverged lineages to date," said Arild Johnsen, professor of zoology and evolutionary biology at University of Oslo and another leader of the study. "The biggest thing is the degree to which we've caught them in the act."

A pair of ravens interact on a branch [Credit: Bjorn Aksel Bjerke/University of Oslo]

How does this relate to people? Humans are also a product of speciation reversal, Omland notes, with the present-day human genome including significant chunks of genetic material from Neanderthals and Denisovans, another less well-known hominid lineage. Recent genetic studies have even indicated a mysterious fourth group of early humans who also left some DNA in our genomes.

"Because speciation reversal is a big part of our own history," Omland said, "getting a better understanding of how that happens should give us a better sense of who we are and where we came from. These are existential questions, but they are also medically relevant as well."

Next steps in the current avian research include analyzing genetic data from ravens who lived in the early 1900s to investigate the potential role of humans in the speciation reversal process. "Getting genomic data out of such old, degraded specimens is challenging," Kearns said, "and all work must be done in a special 'ancient DNA' lab at the Smithsonian's Center for Conservation Genomics."

If those ravens have a similar distribution of genes from the Holarctic and California lineages as the ravens living today, it's unlikely changes in human civilization over the last century played a role.

Co-author John Marzluff, professor of wildlife science at the University of Washington, summed up the experience of being part of the study: "It is fascinating to me that this complex history of raven speciation has been revealed. For decades my students and I held and studied ravens throughout the West and never once suspected they carried evidence of a complex past," he said. "Thanks to collaborations among field workers and geneticists, we now understand that the raven is anything but common."

Source: University Of Washington [March 01, 2018]

Caecilians are serpent-like creatures, but they're not snakes or giant worms. The limbless amphibians, related to frogs and salamanders, favor tropical climates of Africa, Asia and the Americas. Most live in burrows of their own making; some are aquatic.

A limbless amphibian, known as Caecilian, Siphonops annulatus, widely distributed in Brazil. Scientists from Utah State University in the United States and Brazil’s Butantan Institute report skin gland concentrations adapted to different evolutionary pressures in the head and posterior regions of the amphibian [Credit: Carlos Jared, Butantan Institute]

With colleagues from Brazil, Utah State University ecologist Edmund "Butch" Brodie, Jr. reports caecilians feature greatly enlarged poison glands at each end of their bodies, which appear to have evolved from different selective pressures - the ability to tunnel into the ground and to defend oneself from predators.

Brodie, along with Carlos Jared, Pedro Luiz Mailho-Fontana, Rafael Marques-Porto, Juliana Mozer Sciani, Daniel Carvalho Pimenta, and Marta Maria Antoniazzi of São Paulo's Butantan Institute, published the findings in Scientific Reports.

The team's research, supported by the Brazilian National Council for Scientific and Technological Development, focuses on Siphonops annulatus, a caecilian species found throughout Brazil.

"My Brazilian colleagues noticed the burrows made by this species were lined with a shiny, slick substance," says Brodie, professor in USU's Department of Biology and the USU Ecology Center. "We didn't think it was a secretion from the poison glands, so we decided to investigate."

The Brazilian caecilian, grayish in color and measuring about 18 inches in length, is a surprisingly rapid burrower, he says.

Magnified image of connective tissue matrix forming honeycomb structure surrounding glands on the head of Caecilian, Siphonops annulatus. Scientists from Utah State University in the United States and Brazil’s Butantan Institute report skin gland concentrations adapted to different evolutionary pressures in the head and posterior regions of the amphibian [Credit: Carlos Jared, Butantan Institute]

"When caecilians burrow, they force their snouts into the ground and essentially dive into the soil," Brodie says.

As suspected, the team discovered all the skin glands in the serpentine creatures' head region were greatly enlarged, tightly packed mucous glands - not poison ones. The slippery lubrication enables the caecilians' rapid, subterranean escape from predators, especially coral snakes.

"We know of no other amphibian with this high concentration of mucous glands," Brodie says. "In other terrestrial amphibians, mucous is mainly related to the uptake of oxygen. Here, in caecilians, it's obviously used in locomotion."

Examination of the caecilians revealed further information. The mucous glands extend throughout the amphibians' body, in gradually reduced concentration, and give way to poison glands concentrated in the tail.

"The poison glands, resulting from a different selective pressure, provide another defense from predators," Brodie says. "In addition to chemical defense, the tail acts as a 'plug,' blocking the tunnel and further deterring predators."

The eccentric amphibian, Brodie and colleagues write, is "really a box of surprises."

Author: Mary-Ann Muffoletto | Source: Utah State University [February 23, 2018]

Researchers from the University of Melbourne and Museums Victoria have CT scanned all 13 known Tasmanian tiger joey specimens to create 3D digital models, allowing them to study their skeletons and internal organs, and reconstruct their growth and development.

Internal structures of Thylacine joeys [Credit: University of Melbourne]

This has revealed important new information about how this unique extinct marsupial evolved to look so similar to the dingo, despite being very distantly related.

The digital scans show that when first born the Tasmanian tiger or thylacine (Thylacinus cynocephalus) looked like any other marsupial. But three months later, when they left the pouch, they had taken on the appearance of a puppy and continued to grow with a dog-like appearance.

The research, led by the University of Melbourne and Museums Victoria and in conjunction with an international team of scientists, is published in Royal Society Open Science.

The Tasmanian tiger was a marsupial, which raised its young in a pouch. Its resemblance to the dingo is one of the best examples of convergent evolution in mammals. This is where two species, despite not being closely related, evolve to look very similar. The Tasmanian tiger would have last shared a common ancestor with the canids (dogs and wolves) around 160 million years ago.

The specimens cover ages from two to 12 weeks. The white scalebar is 10mm [Credit: University of Melbourne]

Dr Christy Hipsley, Research Associate at the University of Melbourne and Museums Victoria, said after sequencing the Tasmanian tiger genome in 2017, this research fills one more piece of the puzzle on why they have evolved to look so similar to dogs. 

"This is the first digital development series of the Tasmanian tiger, Australia’s most iconic extinct marsupial predator.

"Using CT technology we have been able to garner new information on the biology of this iconic species, and its growth and development."

These scans show in incredible detail how the Tasmanian tiger started its journey in life as a joey that looked very much like any other marsupial, with robust forearms so that it could climb into its mothers pouch. But by the time it left the pouch around 12 weeks to start independent life, it looked more like a dog or wolf, with longer hind limbs than forelimbs.


Once ranging throughout Australian and New Guinea, the Tasmanian tiger disappeared from the mainland around 3000 years ago, likely due to competition with humans and dingos.

The remaining Tasmanian tiger population, isolated on Tasmania, was hunted to extinction in the early 20th century, with the last known individual dying at Hobart Zoo in 1936.

Axel Newton, PhD student and Lead Author on the paper notes, until now there have only been limited details on its growth and development. For the very first time we have been able to look inside these remarkably rare and precious specimens.

Unable to study the living species, the team had to look to the 13 Tasmanian tiger joey specimens that exist in museum collections worldwide, including three from the collection of Museums Victoria. These joey specimens, representing five stages of postnatal development, were scanned using non-invasive X-ray micro-CT scanning technology to create high resolution 3D digital models, in which all their internal structures such as skeleton and organs could be studied.


Associate Professor Andrew Pask from the University of Melbourne explains this was an incredibly effective technique to study the skeletal anatomy of the specimens without causing any damage to them.

"This research clearly demonstrates the power of CT technology. It has allowed us to scan all the known Thylacine joey specimens in the world, and study their internal structures in high resolution without having to dissect or cause damage to the specimen. By examining their bone development, we’ve been able to illustrate how the Tasmanian tiger matured and identify when they took on the appearance of a dog."

The study has also revealed the incorrect classification of two specimens held in the collection of the Tasmanian Museums and Art Gallery (TMAG). Instead, they are most likely to be quolls or Tasmanian devils, based on the number of vertebrate and presence of large epipubic bones (specialised bones that support the pouch in modern marsupials).

Tasmanian tiger [Credit: Tasmanian Museum and Art Gallery, Hobart, Tasmania]

Senior Curator of Vertebrate Zoology at TMAG, Ms Kathryn Medlock, said that the museum had received many requests to dissect its pouch young over the years but requests were always refused.

"One of the major advantages of this new technology is that it has enabled us to do research and answer many questions without destruction of the sample specimens. This is a significant advancement that also has an additional benefit of helping us to learn more about the identity of these specimens that have been in the TMAG collection for many years."

An exciting outcome of the research is that the 3D digital Tasmanian tiger models are to be made publicly available as a resource for current and future researchers.

Source: The University of Melbourne [February 21, 2018]

New research shows that males and females of the same species can evolve to be so different that they prevent other species from evolving or colonising habitats, challenging long-held theories on the way natural selection drives the evolution of biodiversity.

Image showing variations between male and female Liolaemus nigriceps [Credit: Dr Daniel Pincheira-Donoso, School of Life Sciences, University of Lincoln]

According to Darwin's theory of natural selection, first introduced in his book On the Origin of Species (1859), new environments such as mountains and islands with abundant food and habitats, offer species the 'ecological opportunity' to colonise an area using those resources.

New research from the UK has shown that exactly the same mechanism of evolution that creates new species also operates within the same species when males and females compete for the ecological resources available in different habitats, such as bushy areas or stony patches with abundant food. The conflict between the sexes can lead to one sex becoming bigger, more colourful or adapting to eat different food, just like a traditional process of evolution by natural selection can lead an ancestor to split into two different species.

This process of evolution between the sexes expands the biodiversity of the area - a development that evolutionary biologists previously thought only occurred when the number of different species using different resources or 'niches' increases. This new research challenges that assumption, showing that different species and different sexes of the same species can occupy these niches.

Image showing variations between male and female Liolaemus tenuis [Credit: Dr Daniel Pincheira-Donoso, School of Life Sciences, University of Lincoln]

This new research which explored the evolution of lizards in the Chilean Andes Mountains and Argentinean Patagonia, shows that different sexes of the same species can fill niches as well, meaning new species are actively prevented from evolving. This is because there is no new environment for them to occupy - a necessary condition for new species to evolve under Darwin's theory of natural selection.

Conducted by academics from the Universities of Lincoln, Exeter and Sheffield, the study demonstrated that biodiversity can now be seen as the formation of new, different species, or, as the formation of different sexes which are distinct enough to be equivalent to different species in the way they 'saturate' ecological niches.

Dr Daniel Pincheira-Donoso, Senior Lecturer in Evolutionary Biology at the School of Life Sciences at the University of Lincoln and lead researcher on the study, said: "Our research reveals evidence for this intriguing phenomenon that the evolution of sexes within a species could replace the evolution of new species, which begins to add a new layer to our understanding of the evolution of biodiversity.

"It is important to stress that the diversity of life on our planet applies not only to the evolution of different species, but also to the independent evolution of males and females within the same species, which potentially has very important implications."

The findings have been published in the scientific journal Global Ecology and Biogeography.

Source: University of Lincoln [February 21, 2018]

A new theory of plant evolution suggests that the 400 million-year drive of flora across the globe may not have been propelled by the above-ground traits we can see easily, but by underground adaptations that allowed plants to become more efficient and independent.

Researchers from Princeton University and the Chinese Academy of Sciences have posed a theory of plant evolution based on root adaptations that allowed plants to become more efficient and independent. The cross sections above show that the roots of plants such as the subtropical oak species Lithocarpus chintungensis (largest cross section, center left) and the tropical species Parashorea chinensis (lower-right of largest cross section) retained their ancestral thickness and reliance on the symbiotic fungi (purple ring) that surround the root to help it obtain nutrients. As plant species spread from their nutrient-rich tropical origins, however, the root tips of plants such as the desert shrub species Tamarix ramosissima (left of largest cross section) evolved to be thinner so they could more efficiently explore soil for nutrients, and they have less dependence on symbiotic fungi [Credit: Zeqing Ma, Chinese Academy of Sciences]

As plant species spread north and south from their nutrient-rich tropical beginnings, the fine tips of their roots became narrower and more widespread to help them explore increasingly poor soil for vital nutrients, according to a study in the journal Nature led by researchers from Princeton University and the Chinese Academy of Sciences (CAS) in Beijing. In addition, as plants spread into unpredictable environments such as arid deserts they grew less dependent on the symbiotic fungi -- or mycorrhiza -- that colonize roots and help host plants obtain the essential plant nutrients nitrogen and phosphorous.

The findings reconsider how plants adapted to new environments as they evolved, said corresponding author Lars Hedin, the George M. Moffett Professor of Biology and chair and professor of ecology and evolutionary biology and the Princeton Environmental Institute. Scientists have in the past focused on above-ground characteristics, primarily leaf traits and the efficiency with which plants absorb sunlight for photosynthesis, he said.

Instead, Hedin said, he and his colleagues have found for the first time that root diameter and reliance on fungi -- or the lack thereof -- are the traits that most consistently characterize the plant community across entire biomes, which are large distinct communities of animals and plants such as a desert, temperate forest or savanna.

"These are the secret strategies that plants have used over time to take over the world," Hedin said. "Our goal was to unlock the understanding of those strategies, and our findings offer a new global theory for plant evolution. Hidden underground there has been a tremendous game of survival-of-the-fittest and we are fortunate to have the first-ever view of the science of that game.

"This work has major implications for conservation and our stewardship of the plant world," Hedin continued. "It provides some of the hidden, below-ground rules by which plants survive and spread. It's a global view of plant evolution at a time when global rules are essential for building climate models and understanding the biosphere."

Mingzhen Lu, first Princeton author and a graduate student in Hedin's research group, said that if root traits do in fact determine a plant's ability to withstand a particular environment, these findings could be valuable in conserving endangered species or projecting how plants might adapt to climate change.

"Our findings simplify how we can practically characterize a plant's strategy for obtaining nutrients," Lu said. "Knowing their underlying nutrient strategy will help us know how to preserve them, or know the conditions under which they could or could not survive."

Kurt Pregitzer, the Thomas Reveley Professor and dean of the College of Natural Resources at the University of Idaho, said this work could be especially useful in combating invasive species, which, in a highly mobile world, increasingly threaten biodiversity. Pregitzer is familiar with the research but had no role in it.

"Invasive species cause widespread displacement of native plants and tremendous economic impacts across the globe," Pregitzer said. "This study may open entirely new lines of scientific investigation that help us better understand how invasive-plant root systems help these exotic species outcompete native plants."

The researchers spent two years examining a database of root traits consisting of 369 species from seven biomes (above): desert, grassland, Mediterranean, boreal, temperate, subtropical and tropical. Woody biomes are identified as shades of tan-to-yellow and non-woody biomes are in shades of green. The researchers found that plants in tropical (light orange) and subtropical biomes (beige) exhibited the largest range of root-tip diameters, from less than 0.25 millimeters up to 1 millimeter. These plants rely on soil fungi to provide nutrients, a similar strategy to that of Earth's earliest land plants. Plants in biomes characterized by poor soil, cold winters and/or infrequent precipitation have a narrow root-diameter range ideal for that environment. The desert (light green) and grassland (green) species studied all had root diameters of less than 0.25 millimeters [Credit: Lars Hedin and Mingzhen Lu, Department of Ecology and Evolutionary Biology]

The Nature paper is unique for its scale and careful application of scientific methods, Pregitzer said. "This study is the first conducted across a wide range of terrestrial environments and it demonstrates that plant species have evolved root strategies that are conserved within corresponding families, genera and species," he said. "These root traits likely facilitate plant success in highly competitive natural ecosystems."

The researchers spent two years examining a uniquely large database of root traits consisting of 369 species from seven biomes: desert, grassland, Mediterranean, boreal, temperate, subtropical and tropical.

These data were compiled over the course of a decade in the lab of late co-corresponding author Dali Guo, a professor at CAS' Institute of Geographic Sciences and Natural Resources Research. First author Zeqing Ma is a research associate in Guo's lab and co-author Xiangliang Xu is a colleague of Guo's. The paper's co-authors also included root experts Richard Bardgett, professor of ecology at the University of Manchester in the UK; David Eissenstat, professor of woody plant physiology at Pennsylvania State University; and M. Luke McCormack, a research associate at the University of Minnesota.

The researchers found that plants in tropical and subtropical biomes exhibited the largest diameter range for the finest root tips that forage for nutrients, from less than 0.25 millimeters up to 1 millimeter. These thicker-rooted plants employ what the authors call a "conservative" strategy -- similar to that of Earth's earliest land plants -- that relies on the soil fungi prevalent in wet, warm tropical and subtropical soils to provide nutrients. The researchers refer to nutrient-rich soil in consistently sultry environs as "predictable."

Meanwhile, fine-root diameters in "unpredictable" biomes characterized by poor soil, cold winters and/or infrequent precipitation fall within a narrower range ideal for that environment. For instance, the desert and grassland species studied all had root diameters of less than 0.25 millimeters. Root tips in these biomes evolved to be thinner so they could more efficiently explore soil for every unit of carbon the plant expends, and they have less dependence on symbiotic fungi.

The extensive data the researchers used allowed them to explore the evolution of plant roots to an extent never before possible, Lu said. "Below-ground plant ecology has been understudied, limited by a paucity of data," he said. "Because of that, the governing rule of what's going on below ground has been very poorly known."

"Thus far," Hedin added, "everybody has quite naturally tried to understand how plants are organized by looking at above-ground traits. But our findings do not follow the above-ground theories -- that was a surprise."

The study reveals that root and leaf evolution have followed different paths, Pregitzer said. Plant ecologists have known that the form and function of leaves are essential to a plant species' success, but "we did not understand if this was true across the tremendous diversity of plant root systems," he said.

"Interestingly, little was known about how plant roots have evolved to facilitate success in their native habitats," Pregitzer said. "Now we know that leaves and roots have responded to different evolutionary selective pressures, and we can start building a better understanding of how root form and function drive plant success within the tremendous biological diversity we see on Earth."

The findings align with ideas explored at Princeton that suggest that plants -- rather than being passive features of their environment -- have actively adapted to and shaped their environments, Hedin said. He was senior author of a 2015 paper in Nature Plants that suggested that ecosystems take their various forms because plants behave in ways that not only benefit themselves but also determine the productivity and composition of their habitats.

"Over evolutionary time, it's as if plants have actively explored the best strategies to safeguard their own survival," Hedin said. He and Lu brought this perspective to the database put together by their colleagues at CAS.

"We understood from a plant perspective how to bring evolutionary questions to their unique global dataset," Hedin said. "It was this great collaboration where we combined new ideas with years of painstaking fieldwork to produce this great result. It couldn't have happened without both sides."

Source: Princeton University [February 21, 2018]

Using a hitchhiking weed, scientists from the Max Planck Institute for Developmental Biology reveal for the first time the mutation rate of a plant growing in the wild.

Scientists created an 'Evolutionwatch' for plants [Credit: Moises Exposito-Alonso, Claude Becker and colleagues]

They compared 100 historic and modern genomes of the tiny plant Arabidopsis to measure precisely the rate at which it evolves in nature. The oldest plant, preserved in a herbarium, was from 1863. At this time, the scientists estimate the species had already more than 200 years in the New World behind it. Two different methods gave the same result, that Arabidopsis had been introduced by Europeans who arrived on the US East Coast around the year 1600. It was almost certainly introduced there by chance, perhaps carried on the boots of Europeans, or mixed in with the seeds of edible plants.

The team focused on samples from North America, because they knew that one particular genetic family of Arabidopsis was very widespread, presenting an opportunity to observe newly-acquired mutations. The comparison of 100 complete genomes revealed 5000 new mutations, some of which could have given the plant an adaptive advantage as it colonised its new environment. The plant moved inland alongside human settlers, gradually diverging from the European ancestor from which it originated. Samples of the species along the same path today reveal increasingly deep and fast-growing roots, perhaps evidence that it adapted during its hitchhiking trip.

"Collections of invasive populations sampled from different times in history enable us to observe the 'live' process of evolution in action," says Moises Exposito-Alonso, first author of the paper published in PLOS Genetics.

They sequenced the genomes of 100 plants collected by botanists between 1863 and 2006. All samples from before 1990 came from museum collections of dried plants. The oldest dried plants, preserved in time 150 years ago, show how much they had evolved by that time. The youngest plants continued to change and evolve. By comparing genomes of plants that had diverged from a common ancestor for different amounts of times, the scientists calculated how many mutations the plant acquires a year.

This in turn enabled the team to deduce that the last common ancestor of the lineage must have lived at the end of the 16th or beginning of the 17th century, coinciding with the time that many people were arriving by boat from Europe, particularly the southern UK, west coast of France and the Netherlands. This was very surprising, since a previous estimate, which had not made use of genetic information from dried herbarium samples, suggested that the colonizing Arabidopsis plants had only arrived in the 19th century.

Arabidopsis is not a harmful weed, but the findings help reveal some of the fundamental evolutionary processes behind the ability of invasive species to colonise new environments. In particular, they unlock some of the secrets of the "genetic paradox of invasion". This occurs when a colonizer with low genetic diversity is nevertheless surprisingly successful in a new environment.

To determine the effect of new mutations, the scientists grew some of the plants in the lab to identify any differences in growth. The fact that such differences were found suggests that some of the mutations that appeared during the past 400 years conferred an advantage during colonisation.

"We were very surprised, since scientific dogma suggests that evolution normally proceeds at a much slower pace," said Hernan Burbano, one of the supervisors of this study.

"Accurate evolutionary rates for plants and animals will be fundamental to reconstruct their past history and to predict the opportunity of novel advantageous traits to arise. Our results show that herbarium and animal specimens can be the source of a great new branch of genetics in future," Exposito says.

Source: Public Library of Science [February 21, 2018]

On the Himalayan-enveloped Tibetan Plateau and the Altiplano plateau of South America - the world's two highest tabletops - a select few bird species survive on 35 to 40 percent less oxygen than at sea level.

A rendering of avian hemoglobin, the blood protein that captures and delivers oxygen throughout the body [Credit: PNAS]

All extreme-altitude birds have evolved especially efficient systems for delivering that precious oxygen to their tissues. But a new study led by the University of Nebraska-Lincoln and Chinese Academy of Sciences has found that these birds often evolved different blueprints for assembling the proteins - hemoglobins - that actually capture oxygen.

Published in the Proceedings of the National Academy of Sciences, the study found that many species from the two plateaus underwent different mutations to produce the same result: hemoglobins more adept at snaring oxygen from the lungs before sharing it with the other organs that depend on it.

Those mutational differences often emerged even among closely related species residing on the same plateau, the study reported.

"You could imagine, just because of the different ancestral starting points, that the Tibetan birds maybe all went one (mutational) route, and the Andean birds typically did things a different way," said co-author Jay Storz, Susan J. Rosowski Professor of biological sciences at Nebraska. "But that's not what we saw. Across the board, there weren't really any region-specific patterns.

"In both cases, it seems like there were many different ways of evolving a similar alteration of protein function."

Jay Storz stands on the Tibetan Plateau, more than 15,000 feet above sea level. Storz and his colleagues have shown that many high-altitude bird species underwent different mutations to develop the same adaptation: hemoglobin better at capturing and distributing scarce oxygen [Credit: University of Nebraska-Lincoln]

Like all proteins, hemoglobin consists of intricately folded chains of amino acids. The interactions among those amino acids dictate the structure of a protein, which in turn determines its properties - how readily it binds with and releases oxygen, for instance. But a mutation can effectively swap out an amino acid for a chemically distinct version at the same site in the protein, potentially modifying its behavior in the process.

After comparing the ancestral vs. modern hemoglobin proteins of nine species that inhabit the Tibetan Plateau, the team did identify two cases in which distantly related species underwent identical, functionally important mutations. Yet in the other instances, species evolved different ways to build a better hemoglobin.

The latest findings reinforce a 2016 Storz-led study published in the journal Science, which was the first to establish that vertebrate species can follow different molecular-level paths to reach the same adaptation. That study, which investigated birds only from the Andes, inspired the team to follow up with its comparison of Andean and Himalayan species.

"Birds that have adapted to high-altitude conditions from all these different mountain ranges have repeatedly evolved hemoglobin with elevated oxygen affinities," Storz said. "At that (functional) level, everything is highly repeatable, and there's a very striking pattern of convergent evolution. But in terms of the actual molecular underpinnings, there's far less predictability, and it's clear that there are many possible changes that can produce the same functional outcome."

Source: University of Nebraska-Lincoln [February 20, 2018]

Tucked away in an unassuming gray metal file cabinet in a graduate student office at Boston University is an evolutionary puzzle that would leave even Charles Darwin scratching his head. Inside the cabinet, 18 clear Tupperware containers house 301 estrildid finch specimens from New Guinea, carefully laid out in rows by population and species. Each of the 11 species’ plumage is splashed with its own distinct pattern of black, brown, gray, and white.

Credit: Cydney Scott

Michael Sorenson, a professor of biology, explains that the birds are an evolutionary anomaly: Despite their striking coloration differences, all 11 species are extremely closely related, suggesting that they evolved quickly and recently (evolutionarily speaking), even faster than the famous Darwin’s finches of the Galapagos.

But how and why did these close relatives end up looking so different? And how did they evolve so quickly into different species? Biologists have long wondered exactly how new species form, but generally assume that new genetic mutations account for the changes in form and function that ultimately make each species unique. However, that may not always be the case, and studying unusual groups like the finches of New Guinea helps biologists better understand other ways new species emerge, revealing more about evolution as a whole.

“Speciation is the process by which the incredible diversity of life on earth came into being—including humans,” Sorenson says. “It is not only one of the most fundamental processes in evolutionary biology, but is central to understanding the history of life on earth.”

To understand how this extraordinary group of finches evolved, Katie Stryjewski (GRS’15) collected birds throughout New Guinea and carefully preserved blood, feather, and tissue samples, with Sorenson joining her on the last of four trips. Then Stryjewski used genome sequencing to peer deep inside the birds’ genetic codes.

Credit: Katie Stryjewski

Sorenson first became interested in the estrildid finches of New Guinea during the late 1990s, when his research on the indigobirds of Africa snowballed into an ambitious effort to build a family tree of all 145 estrildid finch species in the world.

“My career has been a somewhat less-than-coherent series of studies on out-of-the-ordinary examples of behavior and evolution in birds,” he says. “The unifying theme, however, is an interest in understanding not only the evolution of new species, but also the diversity of behavior and morphology observed in different species.”

Sorenson’s project on estrildid finches started in the hallowed halls of natural history museums around the world.

“Because many of these species occur in remote and far-flung corners of the globe, we often had to use old museum specimens, taking a little feather or a bit of skin from the foot as a source of DNA that would allow us to figure out how all these birds were related,” he explains. “This group of species in New Guinea popped out as very, very closely related.”

Credit: Katie Stryjewski

Sorenson discovered that the entire group of New Guinea finch species was more genetically similar than is typical for the birds within a single African finch species. This points to an “extraordinarily recent and rapid radiation” occurring over tens or hundreds of thousands of years (compared to millions of years for most bird species).

Today, clusters of two to three New Guinea estrildid finch species live in overlapping geographic regions, yet somehow have remained separate species with distinct plumage patterns. For example, both Lonchura grandis and Lonchura castaneothorax (below) live in the same central region of New Guinea, yet look very different.

Sorenson was intrigued. “Which genes are involved? And how many genes does it take to build this species versus that species?” he says. “The profound genetic similarity of these species provided the perfect opportunity to answer these questions.”

To investigate further, he needed higher-quality DNA samples, which meant he had to find a PhD student willing to travel to New Guinea to collect finches in the field. He found Stryjewski, who had developed an interest in tropical birds, and top-notch skills in field research, genetic analyses, and bird taxidermy, as an undergraduate student at Louisiana State University.

Credit: Cydney Scott

“Bird taxidermy is my favorite special skill to mention during icebreaker activities,” Stryjewski says with a laugh. “It’s really more art than science, it’s very delicate, and it takes a lot of practice to do it well. Making specimens, says Stryjewski, allows scientists to create a perfect, permanent record of how a bird looked, and the tissues removed in the process are better for DNA analysis.

Stryjewski made four multiweek trips to New Guinea, traveling throughout the country with the help of local guides, looking for clusters of two or three estrildid finch species living in overlapping geographic areas. Once she found a population of finches, which often live by human settlements, she would set up a mist net.

“I would watch them flying and see what their regular patterns were,” she explains. “And the next morning I would go back before sunrise and set up the net, and they fly right into it.” On their final trip, the hunt for two elusive finch species sent Stryjewski and Sorenson nine hours down the Fly River in the remote Trans-Fly region of Papua, New Guinea, where they and their guides deployed mist nets boatside.

Stryjewski took 20 birds from each population (such as the Chestnut-breasted Munia, Lonchura castaneothorax ramsayi) to make taxidermied specimens.

Credit: Katie Stryjewski (top) and Michael Sorenson (bottom)

She set up a station wherever she was staying (often in the village guest house) and preserved muscle, heart, and liver tissue from each bird in a buffer solution for later DNA sequencing. She also recorded as much additional information as she could, including body measurements, stomach contents, fat content, and the size of internal organs. And she collected blood and feather samples from up to 30 more birds in each population.

Back at BU, Stryjewski used the tissue samples to sequence the birds’ DNA. First, she sampled thousands of tiny DNA snippets from across each bird’s genome, and confirmed that the finch species are “remarkably similar.” This suggests that rather than requiring many changes across the entire genome—how biologists usually think about speciation—it only takes differences in a small number of genes to form a completely new species.

Moreover, different finch species living in the same place, such as the Grey-crowned Munia, Lonchura nevermanni (below, top) and the Black Munia, Lonchura stygia (below, bottom), are often more genetically similar than populations of the same species living in different places.

To pinpoint the genetic differences between species, Stryjewski turned to whole genome sequencing, pooling results from 10 birds in a single population. “Basically you take two different species and you compare their genomes,” Stryjewski explains. “Since they’re really similar all across, anything that’s different should pop out.”

Credit: Katie Stryjewski (top) and Tommy Stryjewski (bottom)

Stryjewski and Sorenson identified about 20 genes that differed among finch species, half a dozen of which are known to control coloration in other organisms, including humans. Different combinations of genes were mixed and matched among species, “as opposed to new mutations cropping up,” Stryjewski says. “Each version of a gene is like a different little thing you could put on a Mr. Potato Head doll, and each bird is collecting a different set of them, and so they all end up looking different.” She and Sorenson published their findings in Nature Ecology & Evolution. The research was supported by the National Geographic Society, the National Science Foundation, and others.

Sorenson adds that “the birds’ genes likely interact with each other in complex ways, making the plumage that results from a particular combination of genes something more than the sum of the parts.” Sorenson thinks that occasional interbreeding between species that live in the same area like the Grey-headed Munia, Lonchura caniceps (below, top) and the Grand Munia, Lonchura grandis (below, bottom) is likely how different versions of genes moved from population to population over time.

Darren Irwin, a zoologist at the University of British Columbia, praises the research for its “elegant analysis of a particularly interesting recent and rapid avian radiation.” He adds that scientists usually think of new species as arising from a single species splitting into two, but “this study provides a great example of how new forms arise in part through mixing genes from other populations.”

Credit: Cydney Scott

Sorenson’s broader goal for the research is to advance general understanding of how evolution works.

“Hopefully it will expand the boundaries of what we know is possible in the process of speciation, and will change scientists’ understanding and perspectives on what exactly species are, and what the minimum requirements are to get the evolution of new species,” he says.

As for the finch specimens, after traveling thousands of miles from New Guinea to BU, they have one more short leg left to their journey: they will cross the Charles River and join the collection at the Harvard Museum of Comparative Zoology.

“I’m pretty excited to donate to Harvard because some of these species they don’t even have, and they’ve only got one or two of the others. They’ll just be preserved there forever,” Stryjewski says. “It’s like the same thing people were doing during the age of exploration, but now we can add this additional layer of the tissue samples and the blood, so their genomes will be preserved as well. It’s a very exciting time to be a zoologist.”

Author: Catherine Caruso | Source: Boston University [February 16, 2018]