Part of the reservoir created by the Serra da Mesa Dam. Felipe Venncio/CC BY 2.0Thanks to the Serra da Mesa Dam in central Brazil, close to 300 islands were created in the span of just two years. More than 650 square miles of the Cerrado region were inundated by the reservoir, which finished filling in 1998. The region is considered a biodiversity hotspot. By so altering the landscape, the dam and reservoir threaten that, but by creating new environments and isolating species, theyre showing how life adapts to all the changes we throw at it.

The hilltops that became islands were once home to a variety of lizards that eat termites, and isolation impacted different varieties of lizards in different ways. Larger species died out (though they survive on the mainland) because they couldnt find enough termites on their islands maintain large body size. So Gymnodactylus amarali, a small gecko, inherited a whole termite buffet.

There was just one problem. For most of the G. amarali geckos, the termites were too big to eatbigger than their mouths. But some of the individual lizards were lucky enough to have slightly larger heads. So they gobbled up termites, thrived, and passed the large-head trait on to their offspring. When scientists from Brazil and the United States compared the island-dwelling lizards with their mainland relativesseparated by only 15 years and a short stretch of waterthe researchers found the island lizards had heads that are about four percent larger. The researchers write in their report that the shift is astonishing because it was so rapid and the lizard populations on the five islands they studied evolved the same trait independently of each other.

It is possible, Science reports, that the larger head size isnt a result of evolution, but rather better growth thanks to the new environment and altered diet. However, the researchers believe evolution explains the size difference, and plan to check for genetic changes in the future.

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A Dam in Brazil Has Altered the Course of Evolution - Atlas Obscura

) at a the laboratory of Santa Fe zoo in Medellin, Colombia. Many species of frogs, including the Golden Frog, the most venomous frog in the world, are in danger of extinction. Photograph: Raul Arboleda/AFP/Getty Images

Although Kermit the Frog has always struggled with body image, in evolutionary terms, the frog body plan is a rather successful one. With a short, stout body, protruding eyes and strong, flexible limbs with webbed feet, the world can be your swamp. The frog body plan has remained rather similar for almost 200m years, and with only limited tweaks in anatomy, frogs (Anura) have managed to occupy a range of different habitats, from muddy pools in Alaska to tree tops in the tropics. Currently, over 6700 species are known from all continents except Antarctica, which makes frogs one of the most diverse and species-rich groups of tetrapods. Never change a good thing. However, this limited variation in the frog body plan over time and space has made it difficult for biologists to reconstruct the evolutionary history of frogs and to sort out who is related to who.

Frogs are amphibians, and the oldest member of the frog lineage the stem-frog Triadobatrachus massinoti which lived during the Early Triassic (~250m years ago) in what is now Madagascar still retained primitive features, such as a tail and the likely inability to jump, that distinguish it from modern frogs. By the Early Cretaceous (131-120m years ago), the first members of the modern frogs have evolved, such as the three-dimensionally preserved Liaobatrachus zhaoi from the Yixian Formation in China (Dong et al., 2013).

The rise of molecular techniques enabled scientists to use DNA instead of morphology to try to unravel the frog family tree. Initial studies focused only on a limited number of genes, and as a result, age estimates for certain groups of frogs varied wildly. Moreover, these studied did little to understand relationships within frog groups, particularly for those groups that contain massive numbers of species, such as the Hyloidea which includes the glass frogs and poison-dart frogs.

A new study by Yan-Lie Feng and colleagues from Sun Yat-Sen University in Guangzhou, China, set out to change this by using an extensive molecular dataset that included 95 different genes from 156 species of frogs. Their dataset represents a major leap compared to previous studies, and has resulted in the best supported timescale of frog evolution thusfar.

By using such a large number of genes and species, this new analysis indicates that the major frog groups are younger than previously thought. The last common ancestor of all living frogs (crown-group Anura) is estimated to have lived during the Upper Triassic at 210m years ago. This is in contrast to previous studies that placed the last common ancestor much further back in time at around 250 million years.

When plotting the diversification of frogs on a geological time scale, it becomes clear that diversification events in frogs coincide with break-ups of major prehistoric landmasses. The first split within Anura is that between the Neobatrachia and other anurans. This split occurs at ~ 180 Mya (Middle Jurassic), at around the same time as the breakup of Pangaea into the two supercontinents Laurasia (northern hemisphere) and Gondwana (southern hemisphere). A second break up occurred at around 135m years ago, when two major lineages of Neobatrachia split into Proceola, containing the superfamily Hyloidea, and Diplasiocoela including the Ranoidea. This split coincides with the separation of South America and Africa and the spreading of the South Atlantic Ocean sea floor in the Early Cretaceous.

Interestingly, three major lineages of frogs, the Hyloidea, Microhylidae and Natatanura, have a near-synchronous origin at around 66m years ago. That estimate overlaps with a major extinction event, the Cretaceous Tertiary (K/T) mass extinction, during which two-thirds of life on earth, including the non-avian dinosaurs, marine reptiles and pterosaurs, went extinct.

Although there is little fossil evidence to show how the K/T mass extinction impacted frogs, it is not unlikely that a number of frog species went the way of the dinosaurs. However, when researchers looked at the rate at which species originated during that time period, the analysis indicated that there was a surge in frog diversification immediately following the K/T boundary. Quite ribbiting, perhaps, is the fact that 88% of current frog species originated in this relatively short time period after the K/T mass extinctions.

Mass extinctions leave behind a wasteland of empty ecological real estate. Species that survive can take advantage of this empty ecological space, and as different organisms invade different niches, they adapt and diversify. This is why mass extinction events are often followed by periods of rapid adaptive radiation and speciation.

The demise of non-avian dinosaurs and many other groups at the end of the Cretaceous triggered explosive radiations of mammals (Alroy, 1999) and birds (Ksepka et al., 2017). This new study on frogs shows that the aftermath of the K/T mass extinction may have provided new ecological opportunities for amphibians as well. Particularly, the increase in forest habitats after the massive loss of vegetation that happened at the K/T boundary is thought to have played a major role in enabling adaptive radiations for arboreal taxa. Truly arboreal species of frogs are limited to groups that originated after the K/T boundary, demonstrating how mass extinctions in the past have shaped the current diversity of frogs. However, as past performance is no guarantee for future success, it remains to be seen how frogs will do in the next round of mass extinction.

References

Alroy, J. 1999. The fossil record of North American mammals: evidence for a Paleocene evolutionary radiation. Systematic Biology 48 (1).

Dong, L., Roek, Z., Wang, Y., and Jones, M.E.H. 2013. Anurans from the Lower Cretaceous Jehol Group of Western Liaoning, China. PLoS ONE 8 (12)

Feng, Y-J., Blackburn; D.C., Liang, D., Hillis, D.M., Wake, D.B., Cannatella, D.C., and Zhang, P. 2017. Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous Paleogene boundary. PNAS 114(29)

Ksepka D.T., Stidham, T.A., and Williamson, T.E. 2017. Early Paleocene landbird supports rapid phylogenetic and morphological diversification of crown birds after the KPg mass extinction. PNAS 114 (30)

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Jump for joy: researchers make huge leap in understanding frog evolution - The Guardian

August 1, 2017 by Eric Hamilton Credit: CC0 Public Domain

After Dan Levitis and his wife lost two pregnancies, before having their three children, he was drawn to investigate why pregnancy loss is so common, and whether other living beings face the same struggle his family did.

Levitis, a scientist in the University of Wisconsin-Madison Department of Botany, had one main suspect in mind: meiosis, which organisms use to produce sperm and eggs for sexual reproduction. He describes meiosis as an intricate cellular line dance, one that mixes up chromosomes to reshuffle genes. This rearrangement helps create offspring that are different from their parents, offspring that might be better equipped to survive in a changing world.

But meiosis is also one of the most complex processes that cells undergo, and a lot can go wrong as chromosomes tangle and untangle themselves. Levitis figured that this complexity might lead to problems creating healthy progeny.

In new research published this week (Aug. 1, 2017) in the Proceedings of the Royal Society B, Levitis and his collaborators report that meiosis takes a heavy toll on the viability of offspring. And not just for humans. Creatures from geckos to garlic and cactuses to cockroaches pay a price to undergo sexual reproduction.

The work provides deeper context on the fundamental biological causes behind pregnancy loss, and suggests that the advantages of sexual reproduction must overcome the severe constraints imposed by meiosis.

"It's known that for humans, the primary cause of pregnancy loss is chromosomal abnormalities arising from meiosis," says Anne Pringle, a professor of botany at UW-Madison and another author of the research. "But what wasn't at all clear was whether meiosis is a leading cause of inviability not just in humans, but wherever it occurs."

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To answer this question, Levitis compared the viability of offspring produced by three different kinds of reproduction. Sexual reproduction, where two players make a genetic contribution, always requires meiosis. On the other hand, asexual reproductionwhere the offspring are clones of their parentsusually uses the much simpler mitosis, a comparatively easy cloning of cells, no genetic reshuffling required. When asexual reproduction does use meiosis, it is even more complicated than sex.

In this three-way comparison, Levitis found that more complex reproduction resulted in lower offspring survival. For example, asexual lizards that use meiosis had lower viability than sexual lizards that also use meiosis because asexual meiosis was more complicated. Yet the organisms that used the simpler mitosis, like palm trees and damselflies, produced healthier offspring.

This pattern held true in 42 of 44 species. "When you get a result that consistent across such a wide range of organisms, it's suspicious," says Levitis. But even after a second look, the data checked out. Something about meiosis, seemingly its complexity, kills offspring.

"If you're making your tally sheet, all the pluses and minuses of sex, the fact that sex requires this deadly process is pretty clearly a disadvantage," says Levitis.

Regarding the evolution of sex, Levitis' findings suggest that the advantages of going through meiosis must be significant enough to balance that tally sheet. The reshuffling of genes between two parents during sex might provide even more of an advantage than previously thought.

The other takeaway, says Levitis, is that although it's easy to think that natural selection can solve every problemand that we might wish it had, such as for high rates of pregnancy losssometimes it comes up against fundamental constraints. Meiosis seems to be one of those insurmountable barriers.

Yet the tradeoff, offspring that are truly unique, with novel genetic combinations to face a challenging world, must be worth it.

Explore further: Researchers identify traffic cop mechanism for meiosis

More information: Is meiosis a fundamental cause of inviability among sexual and asexual plants and animals? Proceedings of the Royal Society B, rspb.royalsocietypublishing.or .1098/rspb.2017.0939

Researchers at NYU and the Whitehead Institute for Biomedical Research have identified the mechanism that plays "traffic cop" in meiosisthe process of cell division required in reproduction. Their findings, which appear ...

Researchers at New York University and the Whitehead Institute for Biomedical Research have identified the mechanism that plays "traffic cop" in meiosisthe process of cell division required in reproduction. Their findings, ...

Alternative splicing significantly expands the form and function of the genome of organisms with limited gene numbers and is especially important for several stages of mouse spermatogenesis.

Why is sex so popular among plants and animals, and why isn't asexual reproduction, or cloning, a more common reproductive strategy?

Where would we be without meiosis and recombination? For a start, none of us sexually reproducing organisms would be here, because that's how sperm and eggs are made. And when meiosis doesn't work properly, it can lead to ...

Geneticists have identified an enzyme which regulates the production of sperm and egg cells in human reproduction.

All animals use a combination of senses to survive. But where the majority typically rely on one or two especially sensitive sensory systems, the oilbird excels by apparently having keen senses all-around.

An unspoken frustration for evolutionary biologists over the past 100 years, says Craig Albertson at the University of Massachusetts Amherst, is that genetics can only account for a small percentage of variation in the physical ...

Interpreting relationships between species and their environments is crucial to inform ecosystem-based management (EBM), a priority for NOAA Fisheries. EBM recognizes the diverse interactions within an ecosystemincluding ...

After Dan Levitis and his wife lost two pregnancies, before having their three children, he was drawn to investigate why pregnancy loss is so common, and whether other living beings face the same struggle his family did.

The first flower to appear along the path of plant evolution, during the time of the dinosaurs, was a hermaphrodite with petal-like organs arranged in concentric circles, researchers said Monday.

Dietary restriction - the reduction of a specific nutrient or total dietary intake without triggering malnutritionincreases longevity and improves learning, but are these processes regulated separately? A new study publishing ...

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Pregnancy loss and the evolution of sex are linked by cellular line dance - Phys.Org

Hyper Evolution: Rise of the Robots, BBC4. Photograph: BBC/Windfall Films/Ed cave

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The season finale of what has been a superb series, of which you trust the Coens themselves would have been proud. Theres a warehouse shootout involving the formidable Kikki and Wrench, Ruby Goldfarb reveals her true colours, and Emmit teeters ever nearer to the brink to which he has been nudged throughout the series. Meanwhile, Gloria and the almost engagingly villainous Varga push towards their final confrontation. Immensely satisfying TV. David Stubbs

Because hip millennials need reality TV, too, you know. This new show follows comedians and real-life couple Bobby Mair and Harriet Kemsley as they plan their wedding. The theme this week is money the pair dont have much, and everything involved with weddings is expensive. Some amusing moments for sure, but the fact is, when youre dealing with a life event like this, its impossible to see the funny side all of the time. John Robinson

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Wednesday's best TV: Hyper Evolution Rise of the Robots; Fargo - The Guardian

Evolution of Panthers won't be noticeable until ball is in the back of the end zone Charlotte Observer What they did in free agency and the draft, for the offense, could probably be qualified more as progressive tweaks than a complete offensive evolution. It's the same playbook, but based on personnel like rookie running back/receiver Christian ... and more »

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Evolution of Panthers won't be noticeable until ball is in the back of the end zone - Charlotte Observer