Convergent evolution

From Andrew Urevig at National Geogaphic: Contradicting some previous accounts, the team argues that this new evidence appears to show that the common ancestor of all panarthropods did not have a complex three-part brain—and neither did the common ancestor of invertebrate panarthropods and vertebrates. … That structure can be traced back through the fossil record. Kerygmachela’s relatively simple brain, preserved as thin films of carbon, includes only the foremost of the three segments present in living arthropods. The researchers are relying on the remarkably hardy tardigrade (water bear) as a surviving example. Not everyone agrees: Tardigrade brains may or may not develop based on segments at all, says Nicholas Strausfeld, a neuroscientist at the University of Arizona who was not Read More ›

From ScienceDaily: A small group of fishes — possibly the world’s cleverest carnivorous grazers — feeds on the scales of other fish in the tropics. The different species’ approach differs: some ram their blunt noses into the sides of other fish to prey upon sloughed-off scales, while others open their jaws to gargantuan widths to pry scales off with their teeth. A team led by biologists at the University of Washington’s Friday Harbor Laboratories is trying to understand these scale-feeding fish and how this odd diet influences their body evolution and behavior. The researchers published their results Jan. 17 in the journal Royal Society Open Science. “We were expecting that with this specialized scale-eating niche, you would get specialized morphology. Read More ›

From Nature: Desert spiders are master engineers A spider living in the Sahara Desert excavates its burrow by hauling out bundles of sand fastened with silken cords, while another carries sand balls in a ‘basket’ of its own bristles. … A similar basket evolved independently in desert ants, the authors note.More. See also: Evolution appears to converge on goals—but in Darwinian terms, is that possible?

From ScienceDaily: Researchers were surprised when sauropterygians with very different lifestyles had evolved inner ears that were very similar to those of some modern animals. “Sauropterygians are completely extinct and have no living descendants,” said Dr James Neenan, lead author of the study. “So I was amazed to see that nearshore species with limbs that resemble those of terrestrial animals had ears similar to crocodylians, and that the fully-aquatic, flippered plesiosaurs had ears similar to sea turtles.” The similarities don’t end there. Some groups of plesiosaurs, the ‘pliosauromorphs’, evolved enormous heads and very short necks, a body shape that is shared by modern whales. Whales have the unusual feature of highly miniaturized inner ears (blue whales have a similar-sized inner Read More ›

“This puts a stake in the heart of the idea of an ancestor with a central nerve cord,” says Greg Wray, an evolutionary developmental biologist at Duke University in Durham, North Carolina. “That opens up a lot of questions we don’t have answers to — like, if central nerve cords evolved independently in different lineages, why do they have so many similarities?” Nature, 2017 It is generally assumed that bilaterians nerve cords evolve from a single Ancestral Nerve Cord but from Amy Maxmen at Nature: Tiny sea creatures upend notion of how animals’ nervous systems evolved: Sweeping study of sea creatures suggests wild deviations over evolutionary time. A study of some of the world’s most obscure marine life suggests that the Read More ›

From ScienceDaily: Travis Hagey, Michigan State University evolutionary biologist, shows how different groups of lizards — geckos and anoles — took two completely different evolutionary paths to developing the beneficial trait of sticky toe pads. In a paper published in the journal Evolution, Hagey showed that anoles seemed to commit to a single type of toe pad, one that generates lots of friction. As a group, they were able to develop sticky toe pads early. Geckos, meanwhile, opted for an evolutionary “drunken stumble,” and seemingly didn’t commit to a single approach, instead evolving toe pads that generate plenty of friction in some species and others that excel at sticking directly to a surface. … “We’re trying to explain how evolution Read More ›

From Jake Buehler at Gizmodo: Imagine an animal with the body of a chameleon, the feet and claws of an anteater, the humped back of a camel, and a tail that is both flattened like a beaver’s, but also like that of a scorpion. If you’re thinking this sounds like someone just threw your local zoo into a blender—or that it’s not far off from mythical creatures like the chimera or manticore—this would be understandable. But this bonkers description fits a real, long-extinct group of tree-dwelling reptiles that lived more than 200 million years ago. Now, a new species of these freaky little critters has been identified, and its fossilized remains pile onto the anatomical strangeness, showing that this ancient Read More ›

Abstract: The archaellum is the macromolecular machinery that Archaea use for propulsion or surface adhesion, enabling them to proliferate and invade new territories. The molecular composition of the archaellum and of the motor that drives it appears to be entirely distinct from that of the functionally equivalent bacterial flagellum and flagellar motor. Yet, the structure of the archaellum machinery is scarcely known. Using combined modes of electron cryo-microscopy (cryoEM), we have solved the structure of the Pyrococcus furiosus archaellum filament at 4.2 Å resolution and visualise the architecture and organisation of its motor complex in situ. This allows us to build a structural model combining the archaellum and its motor complex, paving the way to a molecular understanding of archaeal Read More ›

Convergent evolution of mimetic species confounds classification. From ScienceDaily: The scientists discovered numerous cryptic species-two or more species erroneously classified as one species-as well as single species mistakenly described as two or three. Frequently, species discriminated with genetic data are each others’ closest relatives, but can be distinguished by stark genetic differences; this suggests a lack of interbreeding — a hallmark of species distinctiveness. However, in Elymnias, Lohman and his associates found that cryptic species were unrelated to each other and resulted from a novel cause: mimicry. Different species on different islands of the Indo-Australian Archipelago frequently evolved to resemble a single, widespread model species, and different Elymnias species therefore evolved to resemble each other. Lohman and his colleagues conducted Read More ›

From Sara Reardon at Nature: Wallabies are kicking over scientific conventions surrounding mammalian placentas, the organ responsible for protecting and nourishing a developing fetus. A study finds that contrary to what scientists thought previously, mother tammar wallabies (Macropus eugenii) have both a functioning internal placenta and milk that performs some of the organ’s usual roles. Taxonomists usually separate marsupials — including kangaroos, wallabies and wombats — from placental mammals, also known as eutherians, such as mice and people. The separation is based partly on a supposed lack of a placenta in marsupials. But many researchers think that this distinction is incorrect, noting that marsupials develop simple, placenta-like structures during the end of pregnancy, just before the underdeveloped baby crawls from Read More ›

First, from Casey Luskin in 2014 on Lee Spetner’s The Evolution Revolution here: Many ENV readers might have read, or at least heard of, a well-argued 1996 book by Lee Spetner, Not By Chance. Spetner, who holds a PhD in physics from MIT, has recently published a sequel titled The Evolution Revolution: Why Thinking People Are Rethinking the Theory of Evolution (Judaica Press, 2014). Spetner goes through many examples of non-random evolutionary changes that cannot be explained in a Darwinian framework. He covers some of the natural genetic engineering mechanisms reported by James Shapiro, which can modify an organism’s genome during a period of stress. Of course the big criticism of Shapiro’s arguments is that he never explains how those Read More ›

Integrative biologist Kevin Padian reviews Improbable Destinies: Fate, Chance, and the Future of Evolution by Jonathan B. Losos at Nature. He likes it but with quite a few qualifications: Early in Jonathan Losos’s Improbable Destinies, the narrative goes off the rails. Losos sets up the problem of historical contingency in evolution by repeating the story that 66 million years ago, at the end of the Cretaceous period, an asteroid smacked into Earth, killing off the dinosaurs and paving the way for mammalian success. Had the asteroid missed, he writes, dinosaurs would have continued their domination and we humans might never have evolved. The problem is much evidence has come to light in recent years that he dinosaurs were declining anyway and the Read More ›

From Anurag A. Agrawal and Editor: Judith L. Bronstein at The American Naturalist: Abstract: A charm of biology as a scientific discipline is the diversity of life. Although this diversity can make laws of biology challenging to discover, several repeated patterns and general principles govern evolutionary diversification. Convergent evolution, the independent evolution of similar phenotypes, has been at the heart of one approach to understand generality in the evolutionary process. Yet understanding when and why organismal traits and strategies repeatedly evolve has been a central challenge. These issues were the focus of the American Society of Naturalists Vice Presidential Symposium in 2016 and are the subject of this collection of articles. Although naturalists have long made inferences about convergent evolution Read More ›

From ScienceDaily: Changes in a single color-vision gene demonstrate convergent evolutionary adaptations in widely separated species and across vastly different time scales, according to a study publishing on April 11 in the open access journal PLOS Biology by David Marques of the University of Victoria, British Columbia, and colleagues. The study, which combined genetic analysis with a 19-year-long selection experiment, supports the idea that the mechanisms of adaptive evolution may be more predictable than previously suspected. … “These data support the emerging view in evolutionary biology that mechanisms underlying adaptive evolution are often highly repeatable and thus may be predictable,” said Marques. “They show that evolutionary ‘tinkering’ with a limited set of tools can lead to convergent ‘solutions’ to common Read More ›

From Mike Wehner at Yahoo News: Multiple reports of Tasmanian Tiger sightings are starting to flow in from everyday citizens in Australia. Several people have recently claimed they’ve spotted the animal… The marsupial Thylacine, believed extinct, is really much more like a wolf than a tiger, in appearance and ecological role. Australians have occasionally claimed to have spotted the dog-like animals over the years, but the sightings were typically rare and attributed to nothing more than misidentification. That’s all changed now, as several “plausible sightings” are beginning to give life to the theory that the animal never actually went extinct at all. Now, scientists in Queensland, Australia, are taking action in the hopes of actually finding evidence that the Tiger Read More ›