Galápagos Darwin’s finches evolution, new study

This video says about itself:

May 14, 2012

Darwin’s Finches in the Galapagos: Small Ground-finch, Large Ground-finch, Sharp-beaked Ground-finch (Vampire Finch), Common Cactus-finch, Small Tree-finch, Warbler finch.

From the Biological Journal of the Linnean Society in Britain:

Adaptive divergence in Darwin’s small ground finch (Geospiza fuliginosa): divergent selection along a cline

Article first published online: 14 JUNE 2013


We examine here, in a single year (2005), phenotypic divergence along a 560-m elevation gradient in Darwin‘s small ground finch (Geospiza fuliginosa) in the Galápagos Islands. In this sample, four composite measures of phenotypic traits showed significant differences along the 18-km geographical cline extending from lowlands to highlands.

Compared with lowland birds, highland birds had larger and more pointed beaks, and thicker tarsi, but smaller feet and claws. Finches in an intervening agricultural zone had predominantly intermediate trait values. In a second, mark–recapture study we analyse selection on morphological traits among birds recaptured across years (2000–2005) in lowland and highland habitats.

Birds were more likely to survive in the highlands and during the wet season, as well as if they had large beaks and bodies. In addition, highland birds exhibited higher survival rates if they had small feet and pointed beaks – attributes common to highland birds as a whole. Lowland birds were more likely to survive if they possessed the opposite traits. Selection therefore reinforced existing morphological divergence, which appears to reflect local adaptation to differing resources during the predominantly drought-ridden conditions that characterized the 5-year study. Alternative explanations – including genetic drift, matching habitat choice, deformation by parasites, and the effects of wear – received little or no support.

Why Philornis downsi, the fly that “loves birds”, poses a risk to Finches on Galapagos Islands: here.

Sacred lotus closest to ancestor of flowering plants

This video from India says about itself:

Fruit and unripe seed pod of lotus or Nelumbo nucifera

Dec 19, 2012

Nelumbo nucifera, known by a number of names including Indian lotus, sacred lotus, bean of India, or simply lotus, is a plant in the monotypic family Nelumbonaceae. The Linnaean binomial Nelumbo nucifera (Gaertn.) is the currently recognized name for this species, which has been classified under the former names, Nelumbium speciosum (Willd.) and Nymphaea nelumbo, among others. Names other than Nelumbo nucifera (Gaertn.) are obsolete synonyms and should not be used in current works.

This plant is an aquatic perennial. Under favorable circumstances its seeds may remain viable for many years, with the oldest recorded lotus germination being from that of seeds 1,300 years old recovered from a dry lakebed in northeastern China.

A common misconception is referring to the lotus as a water lily (Nymphaea), an entirely different plant, as can be seen in the center of the flowers, which lack the structure that goes on to form the distinctive circular seed pod in the Nelumbo nucifera.

Native to Tropical Asian nations and Queensland, Australia, it is commonly cultivated in water gardens. It is also the national flower of India and Vietnam.

This footage is part of the professionally-shot broadcast stock footage archive of Wilderness Films India Ltd., the largest collection of imagery from South Asia.

From Big News Network (ANI), Saturday 11th May, 2013:

Sacred lotus bears closest resemblance to ancestor of flowering plants

A team of researchers has reported that they have sequenced the sacred lotus genome, and the results offer insight into the heart of some of its mysteries.

The sacred lotus (Nelumbo nucifera) is a symbol of spiritual purity and longevity. Its seeds can survive up to 1,300 years, its petals and leaves repel grime and water, and its flowers generate heat to attract pollinators.

The sequence reveals that of all the plants sequenced so far – and there are dozens – sacred lotus bears the closest resemblance to the ancestor of all eudicots, a broad category of flowering plants that includes apple, cabbage, cactus, coffee, cotton, grape, melon, peanut, poplar, soybean, sunflower, tobacco and tomato.

The plant lineage that includes the sacred lotus forms a separate branch of the eudicot family tree, and so lacks a signature triplication of the genome seen in most other members of this family, said University of Illinois plant biology and Institute for Genomic Biology professor Ray Ming, who led the analysis with Jane Shen-Miller, a plant and biology professor at the University of California at Los Angeles (who germinated a 1,300-year-old sacred lotus seed); and Shaohua Li, director of the Wuhan Botanical Garden at the Chinese Academy of Sciences.

“Whole-genome duplications – the doubling, tripling (or more) of an organism’s entire genetic endowment – are an important events in plant evolution,” Ming said.

Some of the duplicated genes retain their original structure and function, and so produce more of a given gene product – a protein, for example, he said. Some gradually adapt new forms to take on new functions. If those changes are beneficial, the genes persist; if they’re harmful, they disappear from the genome.

Many agricultural crops benefit from genome duplications, including banana, papaya, sugarcane, strawberry, watermelon and wheat, said Robert VanBuren, a graduate student in Ming’s lab and collaborator on the study.

Although it lacks the 100 million-year-old triplication of its genome seen in most other eudicots, sacred lotus experienced a separate, whole-genome duplication about 65 million years ago, the researchers found. A large proportion of the duplicated genes (about 40 percent) have been retained, they reported.

“A neat thing about the duplication is that we can look at the genes that were retained and see if they are in specific pathways,” VanBuren said.

The researchers found evidence that duplicated genes related to wax formation (which allows the plant to repel water and remain clean) and survival in a mineral-starved watery habitat were retained, for example.

By looking at changes in the duplicated genes, the researchers found that lotus has a slow mutation rate relative to other plants, Ming said.

These traits make lotus an ideal reference plant for the study of other eudicots, the researchers said.

The researchers reported their finding in the journal Genome Biology.

Family tree of all snakes and lizards

This video is called The Beauty of Snakes (Animal Planet Documentary).

From George Washington University in the USA:

Biologist Maps the Family Tree of All Known Snake and Lizard Groups

A George Washington University biologist and a team of researchers have created the first large-scale evolutionary family tree for every snake and lizard around the globe.

The findings were recently published in the journal BMC Evolutionary Biology. Alex Pyron, the Robert F. Griggs Assistant Professor of Biology in GW’s Columbian College of Arts and Sciences, along with researchers from the City University of New York and Arizona State University, detail the cataloging of 4,161 species of snakes and lizards, or squamates.

Squamates include all lizards and snakes found throughout the globe, including around 9,500 species on every continent except Antarctica, and found in most oceans,” said Dr. Pyron. “This is everything from cobras to garter snakes to tiny geckos to the Komodo Dragon to the Gila Monster. They range from tiny threadsnakes that can curl up on a dime to 10 feet monitor lizards and 30 foot pythons. They eat everything from ants to wildebeest.”

The evolutionary family tree, or phylogeny, includes all families and subfamilies and most genus and species groups, said Dr. Pyron. While there are gaps on some branches of the tree, the structure of the tree goes a long way toward fully mapping every genus and species group.

“It’s like building an incomplete family tree for your family, but with half of the ‘children’ sampled. You’re in it, but not your brother, one of your cousins is, but not another. However, because it’s so complete, we know where the missing relatives go because there’s no longer as much mystery as to how the missing species, or cousins, are related, with a few notable exceptions for some remaining species.

“This is also a community effort. We sequenced hundreds of these species ourselves but took thousands more from public databases, building on the work of others.”

Understanding how various snakes and lizards are connected to each other fills a major gap in knowledge, said Dr. Pyron, because before this, there were no single reference for how all lizards and snakes were related or what their classification was.

“A phylogeny and taxonomy is fundamental for all fields of biology that use lizards and snakes, to understand how to classify the species being studied, to interpret biological patterns in terms of relatedness, and even at a more basic level, to count how many species are in an area, for example, for conservation management purposes.”

This project has been in the works since 2008 with the last five years being the most intense. It was funded by the National Science Foundation Postdoctoral Research Fellowship in Biological Informatics.

The researchers used DNA sequencing technology to genotype, or identify, the DNA of thousands of lizards and snakes.

“We have laid down the structure of squamate relationships and yet this is still the beginning,” said Dr. Pyron. “As hundreds of new species are described every year from around the glove, this estimate of the squamate tree of life shows us what we do know, and more importantly, what we don’t know, and will hopefully spur even more research on the amazing diversity of lizards and snakes.”

Tulip tree new discoveries

This is a tulip tree video from the USA.

From the BBC:

16 April 2013 Last updated at 07:10 GMT

Tulip tree‘s genome is ‘molecular fossil’

By Mark Kinver, Environment reporter, BBC News

The “extraordinary level of conservation” of genetic data in the tulip tree remains largely unchanged since the dinosaurs, a study suggests.

The species’ genomic change is about 2,000 times slower than in humans, making it a “molecular fossil”, a team of US researchers said.

The new information has affected our understanding of flowering plants‘ evolution, they added.

The findings have been published in the open access journal BMC Biology.

The team from the universities of Indiana and Arkansas sequenced the mitochondrial genome of the species (Liriodendron tulipifera), only to discover it had one of the slowest silent mutation rates (a process that does not affect gene function).

They added that the sequencing showed that many of the genes that had been lost during 200 million years of flowering plants’ (angiosperms) evolution had been preserved.

“Based on this, it appears that the genome has been more-or-less frozen in time for millions and millions of years,” explained co-author Prof Jeffrey Palmer.

Prehistoric powerhouses

Mitochondria are found within organisms’ cells and their job is to generate power. They do this by converting food stuffs into chemical energy that the organism uses to function.

In an accompanying commentary, Prof Ian Small from the University of Western Australia – who was not involved in the research – said the vast variations between the genetic data of angiosperms gleaned from mitochondrial genome sequencing made “untangling their evolutionary histories difficult”.

However, he added, the paper by Prof Palmer et al turned out to be ” an extremely useful window into the past”.

Prof Small said the species was a member of an “early branching lineage” that was distinct from other groups that housed most of the world’s crop plants, which had been the target of most sequencing efforts around the globe.

As a result of the slow mutation rate, he explained: “This ‘fossilised’ genome gives us some important clues as to what mitochondrial looked like (and how they functioned) as flowering plants evolved and took over the land in the time of the dinosaurs.”

He added that the increasing cost-effectiveness of the sequencing process was making it easier to choose strategically informative species rather than focusing on economically important ones, ie food crops.

He explained that data gaps remained: “The coverage of early diverging plants is still from optimal, with many large and important groups still badly sampled – for example, gymnosperms and ferns.”

He concluded: “I look forward to being able to analyse the next molecular ‘fossil’ to roll off the sequencing machines.”

In detail: Tulip tree

Scientific name: Liriodendron tulipifera
Average height: 20m-30m
Native to the eastern US, and is considered to be one of the region’s tallest native trees
Generally flowers in mid-summer
Distinctive-shaped leaves, which are said to resemble dinosaur footprints
Popular parkland species, as its flowers look similar to tulips
Seeds are wind dispersed, often travelling up to seven times the distance of the mother tree
The timber has a reputation of being resistant to termites

Polar bear-brown bear relationship, new research

This video is called Mother Polar Bear and Cubs Emerging from Den – BBC Planet Earth.

From Wildlife Extra:

DNA study clarifies how Polar bears and brown bears are related

“In retrospect, I think we were wrong about the directionality of the gene flow between polar bears and Irish brown bears,” she said.

March 2013. At the end of the last ice age, a population of polar bears was stranded by the receding ice on a few islands in south-eastern Alaska. Male brown bears swam across to the islands from the Alaskan mainland and mated with female polar bears, eventually transforming the polar bear population into brown bears.

Evidence for this surprising scenario emerged from a new genetic study of polar bears and brown bears led by researchers at the University of California, Santa Cruz. The findings, published March 14 in PLOS Genetics, upend prevailing ideas about the evolutionary history of the two species, which are closely related and known to produce fertile hybrids.

Limited hybridisation

Previous studies suggested that past hybridization had resulted in all polar bears having genes that came from brown bears. But the new study indicates that episodes of gene flow between the two species occurred only in isolated populations and did not affect the larger polar bear population, which remains free of brown bear genes.

At the centre of the confusion is a population of brown bears that live on Alaska’s Admiralty, Baranof and Chicagof Islands, known as the ABC Islands. These bears–clearly brown bears in appearance and behaviour–have striking genetic similarities to polar bears.

“This population of brown bears stood out as being really weird genetically, and there’s been a long controversy about their relationship to polar bears. We can now explain it, and instead of the convoluted history some have proposed, it’s a very simple story,” said co-author Beth Shapiro, associate professor of ecology and evolutionary biology at UC Santa Cruz.

Shapiro and her colleagues analysed genome-wide DNA sequence data from seven polar bears, an ABC Islands brown bear, a mainland Alaskan brown bear, and a black bear. The study also included genetic data from other bears that was recently published by other researchers. Shapiro’s team found that polar bears are a remarkably homogeneous species with no evidence of brown bear ancestry, whereas the ABC Islands brown bears show clear evidence of polar bear ancestry.

More in common with female Polar bears than males

A key finding is that the polar bear ancestry of ABC Islands brown bears is conspicuously enriched in the maternally inherited X chromosome. About 6.5 percent of the X chromosomes of the ABC Islands bears came recently from polar bears, compared to about 1 percent of the rest of their genome. This means that the ABC Islands brown bears share more DNA with polar bear females than they do with polar bear males, Shapiro said.

To understand how hybridization could lead to this unexpected result, the team ran simulations of various demographic scenarios. “Of all the models we tested, the best supported was the scenario in which male brown bears wandered onto the islands and gradually transformed the population from polar bears into brown bears,” said first author James Cahill, a graduate student in ecology and evolutionary biology at UC Santa Cruz.

Cross mating still occurs occasionally

This scenario is consistent with the known behaviour of brown bears and polar bears, according to co-author Ian Stirling, a biologist at the University of Alberta in Edmonton, Canada. Mixing of polar bears and brown bears is seen today in the Canadian Beaufort Sea, where adult male brown bears wander onto the remaining sea ice in late spring and sometimes mate with female polar bears, he said. In areas such as western Hudson Bay and the Russian coast, polar bears are spending more time on land in response to climate warming and loss of sea ice, a behaviour that could have left polar bears stranded on the ABC Islands at the end of the last ice age.

Young male brown bears tend to leave the area where they were born in search of new territory. They may well have dispersed across the water from the Alaskan mainland to the ABC Islands and hybridized with polar bears stranded there when the sea ice disappeared.

“The combination of genetics and the known behaviour of brown and polar bears hybridizing in the wild today tells us how the ABC Islands bears came to be: they are the descendants of many male brown bear immigrants and some female polar bears from long ago,” Stirling said.

The findings suggest that continued climate warming and loss of arctic sea ice may lead to the same thing happening more broadly, said co-author Richard E. (Ed) Green, an assistant professor of bio molecular engineering in UCSC’s Baskin School of Engineering. “As the ice melts in the Arctic, what is going to happen to the polar bears? In the ABC Islands, the polar bears are gone. They’re brown bears now, but with polar bear genes still present in their genomes,” he said.

The first genetic studies of ABC Islands brown bears looked at their mitochondrial DNA, which is separate from the chromosomes and is inherited only through the female lineage. The mitochondrial DNA of ABC Islands brown bears matches that of polar bears more closely than that of other brown bears, which led some scientists to think that the ABC Islands brown bears gave rise to modern polar bears.

Nuclear DNA

The new study looks at the “nuclear DNA” carried on the chromosomes in the cell nucleus. It is the latest in a series of genetic studies of polar bears published in recent years, each of which has prompted new ideas about the relationship between polar bears and brown bears. A 2010 study of fossils and mitochondrial DNA supported the idea that polar bears evolved from the ABC Islands brown bears. But a 2011 study of mitochondrial DNA from extinct Irish brown bears showed an even closer match to polar bears and suggested that polar bears got their mitochondrial DNA from hybridization with Irish bears. Shapiro, a co-author of that study, said she now thinks the Irish brown bears may be another example of what happened in the ABC Islands, but she can’t say for sure until she studies their nuclear DNA.

“In retrospect, I think we were wrong about the directionality of the gene flow between polar bears and Irish brown bears,” she said.

Different theories

Two studies published in 2012 sought to determine when the polar bear lineage diverged from the brown bear lineage using nuclear DNA data. The first, published in April in Science, put the split at 600,000 years ago and concluded that polar bears carry brown bear mitochondrial DNA due to past hybridizations. The second, published in July in Proceedings of the National Academy of Sciences, suggested that brown bears, black bears, and polar bears diverged around 4 to 5 million years ago, followed by repeated episodes of hybridization between polar bears and brown bears.

The new study does not address the question of how long ago polar bears diverged from brown bears, but it may help sort out the conflicting results of recent studies. “It’s a good step in the right direction of understanding what really happened,” Shapiro said.

The study does indicate that the divergence of polar bears from brown bears was only half as long ago as the split between the brown bear and black bear lineages, said Cahill. “We can tell how long brown bears and polar bears have been separate species as a proportion of how long ago they separated from more distantly related species, but putting a year on it is very difficult,” he said.

Green noted that efforts to understand the relationship between polar bears and brown bears has been complicated by the unusual case of the ABC Islands brown bears. “It’s as if you were studying the relationship between humans and chimpanzees and your analysis included DNA from some weird population of humans that had hybridized with chimps. You would get very strange results until you figured that out,” he said.

In addition to Cahill, Green, Shapiro, and Stirling, the co-authors of the new paper include postdoctoral researchers Tara Fulton and Mathias Stiller, undergraduate Rauf Salamzade, and graduate student John St. John at UC Santa Cruz; Flora Jay and Montgomery Slatkin at UC Berkeley; and Nikita Ovsyanikov at the Wrangel Island State Nature Reserve in Russia. Green and Shapiro direct the UCSC Paleogenomics Lab. This research was funded by the Searle Scholars Program.

The great white bears of the frozen north may face a difficult future. Each summer, the sea ice on which they rely to hunt seals is getting thinner and smaller in extent – threatening to upset their way of life: here.

Cliff swallows evolve to avoid traffic

This video from says about itself:

May 31, 2011

A pair of Cliff Swallows building their mud nest under a bridge in Newbury, MA. With the mud being brought to the nest one mouthful at a time this truly is an enormous feat to stick this nest to the underside of a bridge.

From Science in the USA:

Evolution via Roadkill

by Sarah C. P. Williams on 18 March 2013, 12:30 PM

Cliff swallows that build nests that dangle precariously from highway overpasses have a lower chance of becoming roadkill than in years past thanks to a shorter wingspan that lets them dodge oncoming traffic. That’s the conclusion of a new study based on 3 decades of data collected on one population of the birds. The results suggest that shorter wingspan has been selected for over this time period because of the evolutionary pressure put on the population by cars.

“This is a clear example of how you can observe natural selection over short time periods,” says ecologist Charles Brown of the University of Tulsa in Oklahoma, who conducted the new study with wife Mary Bomberger Brown, an ornithologist at the University of Nebraska, Lincoln. “Over 30 years, you can see these birds being selected for their ability to avoid cars.”

The Browns have studied cliff swallows (Petrochelidon pyrrhonota) in southwestern Nebraska since 1982. They return to the same roads every nesting season to perform detailed surveys of the colonies of thousands of birds that build mud nests on bridges and overpasses in the area. Along with studies on living swallows—counting birds and eggs, netting and banding individuals, and observing behaviors—the Browns also picked up swallow carcasses they found on the roads, in the hopes of having additional specimens to measure and preserve. They hadn’t planned studies on roadkill numbers, but recently they began to get the sense that they were picking up fewer dead birds than in the past.

When the researchers looked back at the numbers of swallows collected as roadkill each year, they found that the count had steadily declined from 20 birds a season in 1984 and 1985 to less than five per season for each of the past 5 years. During that same time, the number of nests and birds had more than doubled, and the amount of traffic in the area had remained steady.

The birds that were being killed, further analysis revealed, weren’t representative of the rest of the population. On average, they had longer wings. In 2012, for example, the average cliff swallow in the population had a 106-millimeter wingspan, whereas the average swallow killed on the road had a 112-millimeter wingspan.

“Probably the most important effect of a shorter wing is that it allows the birds to turn more quickly,” says Charles Brown. Previous studies on the dynamics of flight have illustrated the benefits of short wings for birds that perform many pivots and rolls during flying and shown that shorter wings also may allow the birds to take off faster from the ground, he adds.

When the researchers analyzed the average wing length of the living birds in the population, they discovered that it had become shorter over time, from 111 millimeters in 1982 to the 106 millimeter average in 2012. The data suggested to the Browns that roadkill deaths were a major force driving this selection. Birds with longer wings would be more likely to be killed by vehicles and less likely to reproduce, the team reports online today in Current Biology.

The data illustrate a “beautiful trend that never could have been predicted,” says evolutionary biologist John Hoogland of the University of Maryland Center for Environmental Science in Frostburg, who was not involved in the study. “We humans, because we’re changing the environment so much, are adding a new kind of natural selection to these animal populations.”

Few studies have looked at long-term changes in roadkill numbers, Charles Brown says, so more work is needed to determine whether similar trends hold for swallows in other areas, for other types of birds, or for mammals. “I would think that this would be a pattern that certainly might apply to other species,” he says. “But there’s almost nothing in the literature on historical trends in roadkills, because surveys typically last a season or two, not an extended period of years.”

The new findings could also apply to birds killed by wind turbines, Hoogland adds, and they illustrate the payoff that can come with careful data collection and observation. “I think the most important lesson from this research is the paramount importance of collecting data even when you’re not sure what it means or how it could lead to findings in the future.”

Comb jellies, not sponges, most ancient animals?

This is a video about comb jellies from the Vancouver Aquarium in Canada.

From Nature journal:

Genome reveals comb jellies’ ancient origin

Sequencing data challenge sponges‘ claim to primacy in animal kingdom.

Amy Maxmen

08 January 2013

San Francisco

Animals evolved gradually, from the lowly sponge to the menagerie of tentacled, winged and brainy creatures that inhabit Earth today. This idea makes such intuitive sense that biologists are now stunned by genome-sequencing data suggesting that the sponges were preceded by complex marine predators called comb jellies.

Although they are gelatinous like jellyfish, comb jellies form their own phylum, known as ctenophores. Trees of life typically root the comb jellies’ lineage between the group containing jellyfish and sea anemones and the one containing animals with heads and rears — which include slugs, flies and humans. Comb jellies paddle through the sea with iridescent cilia and snare prey with sticky tentacles. They are much more complex than sponges — they have nerves, muscles, tissue layers and light sensors, all of which the sponges lack.

“It’s just wild to imagine” that comb jellies evolved before sponges, says Billie Swalla, a developmental biologist at the University of Washington in Seattle and a leading member of the team sequencing the genome of the comb jelly Pleurobrachia bachei. But the team is suggesting just that, in results they presented at the annual meeting of the Society for Integrative and Comparative Biology, held on 3–7 January in San Francisco, California.

Despite comb jellies’ complexity, DNA sequences in the Pleurobrachia genome place them at the base of the animal tree of life, announced Swalla’s colleague Leonid Moroz, a neurobiologist at the University of Florida in Gainesville. Another team presented results from genome sequencing for the comb jelly Mnemiopsis leidyi, and found that the phylum lands either below, or as close to the base as, sponges on the tree.

“We’ve always thought that predator–prey interactions and sensory adaptations evolved long after the origin of sponges,” Swalla says. “Now we need to imagine early life as a sponge, ctenophore and everything in between.” Because millions of species have gone extinct since animals appeared some 542 million years ago, Swalla says, the ancestor of all animals might look different from modern comb jellies and sponges.

Gene families, cell-signalling networks and patterns of gene expression in comb jellies support ancient origins as well. For example, Moroz and his team found that comb jellies grow their nerves with unique sets of genes. “These are aliens,” Moroz jokes. He suggests that comb jellies might be descendants of Ediacaran organisms, mysterious organisms that appear in the fossil record before animals. Indeed, in 2011, palaeontologists claimed that one of these 580-million-year-old fossils resembled comb jellies1.

Andy Baxevanis, a comparative biologist at the US National Human Genome Research Institute in Bethesda, Maryland, and a leader on the Mnemiopsis genome project, says that comb jellies are the only animals that lack certain genes crucial to producing microRNA — short RNA chains that help to regulate gene expression. Moreover, he points out, sponges and comb jellies lack other gene families that all other animals possess2, 3.

If comb jellies evolved before sponges, the sponges probably lost some of their ancestors’ complexity. Alternatively, says Sally Leys, a biologist at the University of Alberta in Edmonton, sponges may have complexity that scientists have yet to appreciate. “A lot of sponges are more exquisite than a lump on a rock,” she says.

Sceptics wonder whether a high rate of genetic mutation in comb jellies might be causing the lineage to seem closer to the bottom of the tree than it really is. “In the analyses I’ve done, ctenophores are the most problematic taxon. They jump around depending on which genes you use and which animals you include,” says Gert Wörheide, a molecular palaeobiologist at the Ludwig Maximilian University of Munich in Germany. At the meeting, Wörheide presented a tree of life created by comparing ribosomal protein sequences. In it, sponges remained rooted in their bottom-most spot.



  1. Teng, F., Bengtson, S., Wang, Y., Wang, X.-L. & Yin, C.-Y. Evol. Dev. 13, 408–414 (2011).
  2. Maxwell, E. K., Ryan, J. F., Schnitzler, C. E., Browne, W. E. & Baxevanis, A. D. BMC Genom. 13, 714 (2012).
  3. Ryan, J. F. et al. EvoDevo 1, 9 (2010).

Some of the enigmatic Precambrian organisms in the Ediacaran Period grew large and stood tall above the seafloor. Canopy flow modeling suggests that their large size was optimized for access to flow in order to facilitate osmotrophic nutrient uptake in low-flow environments: here.

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