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]

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]

An international team of researchers has produced one of the most comprehensive evolutionary pictures to date by looking at one of the world's most iconic animal families - namely elephants, and their relatives mammoths and mastodons-spanning millions of years.

Crushed dentine from a Woolly Mammoth for DNA extraction [Credit: JD Howell, McMaster University]

The team of scientists-which included researchers from McMaster, the Broad Institute of MIT and Harvard, Harvard Medical School, Uppsala University, and the University of Potsdam-meticulously sequenced 14 genomes from several species: both living and extinct species from Asia and Africa, two American mastodons, a 120,000-year-old straight-tusked elephant, and a Columbian mammoth.

The study, published in the Proceedings of the National Academy of Science, sheds light on what scientists call a very complicated history, characterized by widespread interbreeding. They caution, however, the behaviour has virtually stopped among living elephants, adding to growing fears about the future of the few species that remain on earth.

"Interbreeding may help explain why mammoths were so successful over such diverse environments and for such a long time, importantly this genomic data also tells us that biology is messy and that evolution doesn't happen in an organized, linear fashion," says evolutionary geneticist Hendrik Poinar, one of the senior authors on the paper and Director of the McMaster Ancient DNA Centre and principal investigator at the Michael G. DeGroote Institute for Infectious Research.

"The combined analysis of genome-wide data from all these ancient elephants and mastodons has raised the curtain on elephant population history, revealing complexity that we were simply not aware of before," he says.

Graduate student Emil Karpinski holds a tibial cross section from a Siberian Woolly Mammoth. This permafrost preserved sample still contains fat entombed marrow [Credit: JD Howell, McMaster University]

A detailed DNA analysis of the ancient straight-tusked elephant, for example, showed that it was a hybrid with portions of its genetic makeup stemming from an ancient African elephant, the woolly mammoth and present-day forest elephants.

"This is one of the oldest high-quality genomes that currently exists for any species," said Michael Hofreiter at the University of Potsdam in Germany, a co-senior author who led the work on the straight-tusked elephant.

Researchers also found further evidence of interbreeding among the Columbian and woolly mammoths, which was first reported by Poinar and his team in 2011. Despite their vastly different habitats and sizes, researchers believe the woolly mammoths, encountered Columbians mammoths at the boundary of glacial and in the more temperate ecotones of North America.

Strikingly, scientists found no genetic evidence of interbreeding among two of the world's three remaining species, the forest and savanna elephants, suggesting they have lived in near-complete isolation for the past 500,000 years, despite living in neighbouring habitats.

These are African savanna elephants in the San Diego Zoo. In the middle is Swazi, the female elephant from which the reference genome was sequenced [Credit: San Diego Zoo Global]

"There's been a simmering debate in the conservation communities about whether African savannah and forest elephants are two different species," said David Reich, another co-senior author at the Broad Institute who is also a professor at the Department of Genetics at Harvard Medical School (HMS) and a Howard Hughes Medical Institute Investigator. "Our data show that these two species have been isolated for long periods of time - making each worthy of independent conservation status."

Interbreeding among closely related mammals is fairly common, say researchers, who point to examples of brown and polar bears, Sumatran and Bornean orangutans, and the Eurasian gold jackal and grey wolves. A species can be defined as a group of similar animals that can successfully breed and produce fertile offspring.

"This paper, the product of a grand initiative we started more than a decade ago, is far more than just the formal report of the elephant genome. It will be a reference point for understanding how diverse elephants are related to each other and it will be a model for how similar studies can be done in other species groups," said co-senior author Kerstin Lindblad-Toh, a senior associate member of the Broad Institute and Director of the Science for Life Laboratory at Uppsala University in Sweden.

"The findings were extremely surprising to us," says Eleftheria Palkopoulou, a post-doctoral scientist in at HMS. "The elephant population relationships could not be explained by simple splits, providing clues for understanding the evolution of these iconic species."

Researchers suggest that future work should explore whether the introduction of new genetic lineages into elephant populations-both living and ancient-played an important role in their evolution, allowing them to adapt to new habitats and fluctuating climates.

Source: McMaster University [February 26, 2018]

The tropical rainforests of Central and South America are home to the largest diversity of plants on this planet. Nowhere else are there quite so many different plant species in one place. However, the entire region is increasingly threatened by human activity, which is why researchers are stepping up their efforts to record this astonishing biodiversity and find out how it developed. In a project undertaken by Johannes Gutenberg University Mainz (JGU) in collaboration with Dutch research institutions, the causes of this plant diversity were investigated by studying two closely related groups of trees of the Annonaceae family.

Cremastosperma brevipes, French Guiana [Credit: Paul J. M. Maas]

The researchers identified three relevant factors: the formation of the Andes mountain range, the disappearance due to natural causes of the extensive Pebas wetlands system that once existed in the Amazon region, and the formation of a land bridge between Central and South America in the form of the Panama Isthmus.

Cremastosperma and Mosannona are two genera of the Annonaceae or custard apple family the habitat of which is neotropical rainforests, where they extend from the lowlands up to elevations of 2,000 meters. They are primarily found in the Andes region of South America, but also as far north as Central America.

Mosannona costaricensis, Costa Rica [Credit: Reinaldo Aguilar]

The team of botanists led by Dr. Michael Pirie, who joined JGU as a researcher in 2013, looked at the distributions of the various species of both genera and their phylogenetic history in order to determine the influence of the geological upheavals on the continent.

For this purpose they compiled a time-calibrated phylogenetic tree based on DNA data, using the so-called molecular clock technique which is calibrated using the ages of the available fossils. In total, they analyzed 11 species of the genus Mosannona and 24 species of the genus Cremastosperma.

Formation of the Andes, the Isthmus of Panama, and the drying-out of the Pebas wetland system all promoted diversification

The research has produced a biogeographical scenario that confirms in this context the significance of the geological history of north-western South America during the late Miocene and early Pliocene periods about 5 to 10 million years ago.

Cremastosperma yamayakatense, Peru [Credit: Michael Pirie]

"We have actually discovered that the diversification of these two plant genera took place in parallel with major geological events, namely the formation of the Andes, the drying-out of the Pebas system, and the development of a land bridge to Central America," explained Pirie. Cremastosperma species, for example, were able to spread into what is today the Amazon basin and diversify, once the wetlands had silted up due to the deposition of material from the rising Andes.

One way in which diversification can be stimulated is by migration into a new ecosystem while another is adaptation to new conditions. "Natural changes over longer periods provide plants with a chance to adapt," added Pirie. On the other hand, rapid changes, such as those that have occurred in the recent past, do not give plants sufficient time to evolve.

Cremastosperma leiophyllum, Bolivia [Credit: Lars W. Chatrou]

While the development of the two genera in line with geological conditions could be said to be more or less as might be expected, the biologists did find one clear difference between them. Although their distribution patterns mostly overlap, Cremastosperma species and Mosannona species to some extent dispersed along differing routes. In the case of Cremastosperma, colonization of an area in what is now Guyana began from north-western South America at a time before the last parts of the Andes developed and could form a barrier. Mosannona, on the other hand, began to spread here at a far later date from its base in the Amazon basin.

Taxonomic update to include five new species

Dr. Michael Pirie will be continuing his research work in 2018 with the aid of a grant from the Heisenberg Program of the German Research Foundation (DFG). This will also involve publication of an extensive monograph in which a total of 34 Cremastosperma species will be described, including five new species that Pirie and his colleagues have recently discovered.

The study is published on Royal Society Open Science.

Source: Universitat Mainz [Febraury 26, 2018]

Lizards have special superpowers. While birds can regrow feathers and mammals can regrow skin, lizards can regenerate entire structures such as their tails. Despite these differences, all have evolved from the same ancestor as lizards.

The Anolis auratus is one of several lizard species studied as part of new research comparing lizard genomes - their entire DNA code - to those of other animals [Credit: Kenro Kusumi]

Spreading through the Americas, one lizard group, the anoles, evolved like Darwin's finches, adapting to different islands and different habitats on the mainland. Today there are more than 400 species.

Constructing a family tree for three lizard species collected in Panama at the Smithsonian Tropical Research Institute (STRI) and a fourth from the southeastern U.S., scientists at Arizona State University compared lizard genomes -- their entire DNA code -- to those of other animals.

The researchers discovered that changes in genes involved in the interbrain (the site of the pineal gland and other endocrine glands), for color vision, hormones and the colorful dewlap that males bob to attract females, may contribute to the formation of boundaries between species. Genes regulating limb development also evolved especially quickly.

"While some reptiles such as tortoises changed remarkably little over millions of years, anole lizards evolved quickly, generating a diversity of shapes and behaviors," said Kenro Kusumi, corresponding author and professor at ASU School of Life Sciences. "Now that sequencing entire genomes is cheaper and easier, we discovered molecular genetic evidence for rapid evolution that may account for striking differences between bodies of animals living in different environments."

Kusumi's lab, working with colleagues at the University of Arizona College of Medicine-Phoenix, is especially interested in how reptiles' genomes shape their ability to regenerate and to develop a diversity of body forms.

"This is the first time the complete genetic code -- the genome -- of any vertebrate species from Panama has been sequenced and analyzed," said Oris Sanjur, co-author and Associate Director for Science Administration at STRI. "Information from these three species is an important contribution to our understanding of biodiversity and the evolution of new species."

The Anolis apletophallus is one of several lizard species studied as part of new research comparing lizard genomes - their entire DNA code - to those of other animals [Credit: Kenro Kusumi]

Scientists estimate that there are 40 species of anolid lizards living in Panama, compared to only one in the U.S. A team from ASU collected three species with permission from the Ministry of the Environment, MiAmbiente: the Central American giant anole, Anolis frenatus, lives high on tree trunks; the grass anole, A. auratus, perches on bushes or on grassy vegetation and the slender anole, A. apletophallus, found only in Panama, hangs out lower on tree trunks or on the ground.

Researchers at ASU's School of Life Sciences lined up the DNA sequences of the lizards with the DNA sequences of 31 other animals: the lobe-finned fish and the four-legged animal groups that evolved from them. They also took a careful look at genes that code for proteins: more than 22,000 genes in the green anole, A. carolinensis, versus approximately 20,000 identified each in A. auratus and A. frenatus and 13,000 in A. apletophallus.

One obvious explanation for a faster rate of evolution is the anole lizards' faster rate of reproduction. Anoles typically mate in their first year of life, while other reptiles take much longer to reach sexual maturity. They also breed with many other individuals so mutations that make it difficult for individuals to survive are eliminated fairly quickly.

The first and only other anole lizard to be sequenced previously was the green anole, A. carolinensis, the only anole species resident in the U.S. In that study from MIT, the A. carolinensis genome held evidence of more recent evolution and the loss of ancient repeated elements in the part of the DNA that does not code for proteins. In this sense, it was important to sequence the three Panamanian species, because the U.S. species may not be the most representative of the diverse anole group.

"For 15 years, an impressive amount of time and money poured into discovering the genomes of mammals, motivated by our drive to understand human evolution and to look for cures for disease. Even though the squamate reptiles include more than 10,000 species -- almost double the number of mammal species -- a single genome was not enough to understand the variability within this group," said the first author of the report, Marc Tollis, a post-doctoral fellow at ASU.

"By comparing these four anole lizard genomes, we're beginning to understand how one of the most diverse groups of vertebrates regenerate, develop and diversify," he added.

The study is published in Genome Biology and Evolution.

Source: Arizona State University [February 23, 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]

ETH scientists have been able to prove that a protein structure widespread in nature – the amyloid – is theoretically capable of multiplying itself. This makes it a potential predecessor to molecules that are regarded as the building blocks of life.

Lakes in volcanic surroundings could have been the breeding ground for the first biochemical compounds around 4 to 4.5 billion years ago [Credit: Dhilung Kirat/Wikimedia, ETH Zurich]

Long regarded as a biological aberration, amyloids are fibrous aggregates of short protein fragments. Amyloids have a bad reputation because they are thought to be the cause of multiple neurodegenerative diseases, including Alzheimer’s, Parkinson’s and Creutzfeldt–Jakob disease.

It was only recently that researchers discovered that amyloids appear as structural and functional building blocks in a wide range of life forms, from bacteria, yeast and fungi to humans. In vertebrates, they play a role in the production of the pigment melanin, while yeast cells use amyloid aggregates to form a kind of molecular memory.

Catalysts in prebiotic evolution

Composed of short peptides, amyloid fibres can accelerate chemical reactions in a similar way to enzymes; they have thus been viewed for several years as candidates for the first precursor molecules of life. Until now, however, an important chemical property was lacking in the theory of amyloids role in abiogenesis: self-replication.

Left: electron micrograph of an amyloid fibre. In green is a diagram of the sheet structure characteristic for amyloids, consisting of multiple short peptide chains [Credit: Jason Greenwald/ETH Zurich]

Early proponents of the amyloid hypothesis include ETH Professor Roland Riek and his senior assistant Jason Greenwald, from the Laboratory of Physical Chemistry. In an experiment, they have now been able to show that amyloids can serve as a chemical template for the synthesis of short peptides. And the critical point: “This ability also potentially applies to the amyloid itself – meaning the molecules can self-replicate,” says Riek. The researchers reported their findings in a study in Nature Communications.

Template for self-replication

The ability to self-replicate is regarded as an essential prerequisite for every early form of life. By proving that amyloids self-replicate, Riek and his team have not only highlighted another amazing aspect of this commonly underestimated protein, but also filled in a previously missing link in the amyloid hypothesis’ argument.

Almost two years earlier, the ETH scientists had already proven in an experiment that amyloid structures can spontaneously form with astounding ease – from simple amino acids that probably already existed when the Earth was still lifeless, and under reaction conditions that appear very plausible for the primordial soup.

The self-replication mechanism of amyloid fibres depicted schematically: piece by piece, specific amino acids (coloured building blocks) settle at the right site and chemically combine. During the process, the growing amyloid serves as a template for itself [Credit: Lukas Frey/ETH Zurich]

The same is true for the newly discovered peptide synthesis: “The reaction mechanism seems to be of a general nature. It is stable over a wide range of temperatures and salt concentrations, in both acidic and alkaline environments,” explains Greenwald.

This discovery strengthens the researchers’ opinion that early in evolutionary history, amyloids could have played a central role in the development of early life forms as information carriers and catalytic units.

Not just an RNA world

Until now, however, the most widespread idea for the molecular beginnings of life has been the RNA hypothesis, which sees ribonucleic acid (RNA) as the only key player in the prebiotic primordial soup. This is because, like the genetic material DNA, RNA molecules can code information, and are also able to self-replicate.

The ETH researchers are now picking away at the prevailing dogma of an RNA-based world. They think that the amyloid hypothesis is more plausible; firstly, because RNA molecules with a biological function are much larger and more complex, so they are unlikely to form spontaneously under prebiotic conditions. “Additionally, amyloids are much more stable than early nucleic acid polymers, and they have a much simpler abiotic synthesis route compared to the complexity of known catalytic RNAs,” says Greenwald.

Riek adds: “We will never be able to prove which is true – to do so, we would have to turn back the last 4 to 4.5 billion years of evolution. However, we suspect that it was not one, but multiple molecular processes with various predecessor molecules that were involved in the creation of life.”

Author: Michael Keller | Source: ETH Zurich [February 22, 2018]

It’s so impressive: a living cell is able to neatly package a big jumble of DNA, over two meters in length, into tidy, tiny chromosomes while preparing for cell division. For over a century, it has been clear that a cell can do so, but scientists have been puzzled for decades on how the process works.

Artist impression of a condensin protein complex creating a loop in DNA [Credit: Cees Dekker Lab TU Delft/Scixel]

Researchers from the Kavli Institute of Delft University and EMBL Heidelberg now managed for the first time to isolate and film the process, and witnessed—in real time—how a single protein complex called condensin reels in DNA to extrude a loop. By extruding many such loops in long strands of DNA, a cell effectively compacts its genome so it can be distributed evenly to its two daughter cells. The scientists published their findings online in Science.

Spaghetti

This major discovery resolves a heated debate in the field, as it finally answers a question that has been discussed in biology for over a century: Before dividing in two, DNA in a cell is comparable with spaghetti – a messy mixture of intermingled strands. The cell needs to organise this jumble in chromosomes to be able to divide its DNA neatly over both daughter cells.


For many years, it has been clear that a protein complex called ‘condensin’ plays a key role, but until now, biologists were divided on exactly how. One theory stated that condensin works like a hook that can grasp and connect DNA within the jumble of DNA, thus tying it together. Another theory suggested that the ring-shaped condensin pulls the DNA inwards to create a loop.

Motor function

In a cover article in Science last November, scientists from Delft and collaborating labs showed that condensin indeed has the motor function needed for such loop extrusion. This added an important new piece to the puzzle, but as Kim Nasmyth from Oxford University—one of the leading scientists in the field of DNA organisation—noted in the accompanying perspective in Science, “the discovery that condensin is a DNA translocase is certainly consistent with the idea that it functions as a loop extruder, but by no means proves it. The challenge will be to observe extrusion as well as translocation, to establish whether it is a property of individual or multimeric complexes, and to elucidate the molecular mechanism.”

Resolving the mystery

And this is exactly what has now been accomplished. Scientists from the Cees Dekker group at the Kavli Institute of Delft University, together with the Christian Haering group from EMBL Heidelberg who established the purification and fluorescence labeling of the protein, managed to make actual movies that caught the action of the condensin complex in the act – that is, while it was extruding a loop of DNA.


“We’ve simply proved it by filming it,” says Mahipal Ganji, a postdoc in the group of Cees Dekker at Delft. “DNA is such an entangled mishmash, that it is very difficult to isolate the process and study it in cells. In our study, the first step was to fix the two ends of a DNA molecule onto a surface and put colour dyes on the DNA and condensin. By then applying a flow in the fluid perpendicular to the molecule, we oriented the DNA in a U-shape and brought it into the focal plane of our microscope. Amazingly, we could then see a single condensin bind and start extruding a loop.”

Fuel

Prof. Cees Dekker adds, “This settles the debate. These data provide compelling evidence that condensin indeed reels in DNA to form loops. Our novel imaging approach also allows measurement of all kinds of quantitative data: the symmetry of the loop extrusion, the speed at which the loop is formed, what happens when you pull on the DNA.”

The looping speed was found to be remarkably high: up to 1500 base pairs of DNA can be reeled in by condensin per second. And it does so while consuming only a modest amount of ATP—the ‘fuel’ of the condensin motor—indicating that condensin does not step along the DNA base by base, but pulls it in large steps. When slightly pulling on the DNA, the looping process slows down. Apparently, with tension, condensin seems to struggle more to create a loop.


Unexpectedly, the loop extrusion is asymmetric: “We saw that condensin docks onto DNA and anchors itself there, and then starts reeling in DNA from one side only.” Dekker adds, “Yet another interesting finding.”

Medical relevance

The research represents a significant step in the fundamental understanding of DNA in our cells, but it is also relevant for medical research. Problems with the protein family to which condensin belongs—the SMC proteins—are related to hereditary conditions such as Cornelia de Lange Syndrome. Condensin is also crucial in the organisation of the chromosomes during cell division, and errors in the process can result in cancer. A better understanding of these processes is vital for tracking down the molecular origins of serious illnesses.

Source: Delft University of Technology [February 22, 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]