Charles Darwin

Scientists Finally Solve Charles Darwin’s ‘Abominable Mystery’

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For many years, Charles Darwin was haunted by flowers. In 1859, the naturalist published his most famous work, On the Origin of Species, the book that is generally regarded as the foundation of evolutionary biology. But 20 years later, he was still bothered by one big thing: Where the heck did all the flowers come from? In a letter to botanist Joseph Dalton Hooker in 1879, Darwin called this problem an “abominable mystery.” It might sound silly, but Darwin really couldn’t explain how flowering plants — known as angiosperms — had risen to dominance so quickly over the more primitive angiosperms — a group that includes pines and palms.

 Field%20of%20lavender%20flowers.

The fossil record shows us that around 100 million years ago, during the Cretaceous period, a huge variety of angiosperms came onto the scene and replaced gymnosperms as the dominant type of plant on Earth. This sudden abundance of plants — the ancestors of modern lavender, wheat, roses, magnolias, daisies, and so forth — ran counter to Darwin’s theory that new species arise very slowly over time as a result of selective pressures. Current hypotheses suggest that most angiosperms evolved alongside the insects or other animals that pollinate them, without which it’s not possible for the plants to produce seed-bearing fruits. But these hypotheses don’t explain the epic boom in ancient angiosperms.

Magnolia
The magnolia is one of the most ancient existing angiosperms, with fossil relatives appearing as long as 95 million years ago.

In a paper published Thursday in the journal PLOS Biology, a couple of scientists proposed an answer to the abominable mystery of why angiosperms replaced gymnosperms so abruptly. Kevin Simonin, an assistant professor of ecology and evolution at San Francisco State University, and Adam Roddy present evidence that it all comes down to the efficiency of cells. The secret to angiosperms’ success, they say, is a rapid downsizing of the plants’ cells beginning about 140 million years ago. This downsizing dramatically increased their efficiency. Once angiosperms became that much more efficient, their domination of terrestrial ecosystems was only a matter of time.

The research team arrived at this conclusion by examining the relative size of genomes in angiosperms and gymnosperms, then comparing those numbers with the plants’ carbon dioxide capture capacity and liquid transfer efficiency. Cell sizes can vary a lot due to various factors, but genome size is a strong predictor of cell size. Therefore, they concluded, a smaller genome means a smaller cell — and therefore more cells can be packed into the same volume of plant tissue, enabling a plant to take in more carbon dioxide and water, thereby producing more carbohydrates that yield energy and drive growth.

Gingko leaf
Angiosperms like Gingko biloba used to cover the Earth.

Photosynthesis is a big part of this picture, too since, as we all know, plants need sunlight to turn water and carbon dioxide into carbohydrates. Previous research has established that the higher photosynthetic capabilities of angiosperms helped them grow much more quickly than their gymnosperm cousins, but this new study shows us how angiosperms achieved this high level of efficiency.

So even though coevolution with pollinators played a huge roll in the specific mechanisms of angiosperm evolution, Simonin and Roddy say there’s something common to all of these plants, something fundamental to their biophysical architecture, that enabled them to take over the world. Perhaps this research would set Darwin’s mind at ease. But more likely, he would just have new questions.

Abstract: The abrupt origin and rapid diversification of the flowering plants during the Cretaceous has long been considered an “abominable mystery.” While the cause of their high diversity has been attributed largely to coevolution with pollinators and herbivores, their ability to outcompete the previously dominant ferns and gymnosperms has been the subject of many hypotheses. Common among these is that the angiosperms alone developed leaves with smaller, more numerous stomata and more highly branching venation networks that enable higher rates of transpiration, photosynthesis, and growth. Yet, how angiosperms pack their leaves with smaller, more abundant stomata and more veins is unknown but linked — we show — to simple biophysical constraints on cell size. Only angiosperm lineages underwent rapid genome downsizing during the early Cretaceous period, which facilitated the reductions in cell size necessary to pack more veins and stomata into their leaves, effectively bringing actual primary productivity closer to its maximum potential. Thus, the angiosperms’ heightened competitive abilities are due in no small part to genome downsizing.

Malaria threat to Galapagos birds

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Blue-footed booby
The blue-footed booby was first extensively studied by Charles Darwin on his visit to the Galapagos

The Galapagos Islands may have inspired Charles Darwin’s theory of evolution, but scientists fear some of the species he observed may not be capable of adapting to new environmental challenges.

Experts say the introduction of foreign parasites to the islands and the increase in frequency of El Nino events, which scientists recently attributed to global warming, could push bird species in the Galapagos towards extinction.

“The situation is precarious,” says Dr Patricia Parker, Endowed Professor of Zoological Studies at the University of Missouri St Louis (UMSL), “particularly for species such as the Galapagos penguin, which live in very small populations.”

The Galapagos Islands

  • The Galapagos Islands comprise a volcanic archipelago west of Ecuador
  • Together the islands have an area of just over 8,000 sq km (3,000 sq mi)
  • They are well known for a huge number of species that are unique to the islands (endemic)
  • Charles Darwin studied the islands’ wildlife during the voyage of the Beagle
  • His observations made a significant contribution to his theory of evolution by natural selection

Foreign parasites have contributed to mass extinctions in Hawaii, which has lost up to 30% of its endemic birds.

Hitherto, the Galapagos Islands have avoided a similar fate. But Dr Parker, who contributed towards a new report about avian malaria on the archipelago, believes it could be just a matter of time before the virus claims its first species.

The disease is already prevalent in the yellow warbler and Galapagos penguin, which has an estimated population of just 3,000 individuals.

The parasite that causes avian malaria (Plasmodium) requires passage through the digestive and circulatory systems of a biting insect in order to reproduce.

“The insect is considered the primary host of the parasite,” explains Dr Parker.

Suitable hosts

However, for the Plasmodium parasite to complete its life-cycle it must then be transmitted to a suitable bird host through the saliva of the biting insect.

“The parasite then goes through a massive multiplication phase in the liver of the animal before entering the bloodstream,” says Dr Parker. “From there, the next biting insect that takes a blood meal picks them up.”

But not all birds are competent hosts.

“We are trying to identify which species of mosquito is responsible for vectoring it and which bird species is the reservoir for this parasite,” says Dr Parker.

After studying 3,726 samples from 22 endemic birds, Dr Parker and her team – scientists from UMSL, Galapagos National Park, Charles Darwin Foundation and Saint Louis Zoo – believe the parasite is not completing its life-cycle in endemic birds.

Yellow warbler The disease is already prevalent in the yellow warbler

“We don’t think Galapagos natives are part of the transmission cycle,” says Dr Parker. “They become infected but they don’t actually allow the parasite to complete its life-cycle.”

Attention has now shifted to three introduced birds; the domesticated fowl, the cattle egret and the smooth-billed ani, a species thought to have been brought here by farmers because it removes ticks from cattle.

“If we discover that one of these introduced species is responsible for the transmission of this potentially dangerous parasite then the Galapagos National Park would consider whether they want to mount an eradication effort,” says Dr Parker.

“There is a sense of urgency about this because it’s only a matter of time until one of the endemic birds will become a successful host – all host and parasite relationships evolve.”

Scientists suspect an introduced mosquito is acting as the primary host and, if this is confirmed, authorities will also consider eradicating the insect.

The Galapagos National Park has experience exterminating foreign species, having successfully eliminated disease-spreading rock pigeons.

El Nino year

However, preserving native species could prove trickier; scientists say global warming is likely to increase the frequency of El Nino events, which can have a devastating effect on Galapagos wildlife.

“In the El Nino events of 1982 and 1996 the population of penguins declined to approximately 300 and 400 individuals respectively,” says Gustavo Jimenez, wildlife veterinarian at the Charles Darwin Foundation.

“The increased frequency of El Nino could mean there is not enough time for the recovery of the species that are affected, which would lead not only to their populations reaching critically low numbers but possibly extinction.”

Galapagos penguin An increased frequency of El Nino events and avian malaria could consign the Galapagos penguin to history

During El Nino, the Humboldt Current, which brings cold, nutrient-rich waters from Antarctica, is reversed.

“Instead what hits the islands are warm equatorial waters,” explains Dr Parker. “So the birds that rely on marine life; their numbers plummet.”

Scientists fear future El Nino events coupled with an outbreak of avian malaria could consign species such as the Galapagos penguin and flightless cormorant to the history books.

“It is possible that in a situation where there are multiple environmental stresses – less food, strange weather conditions and so on – these Plasmodium infections might be much more damaging than they appear to be under more benign circumstances,” says Dr Parker.

On the edge

Concern is also mounting for the critically endangered mangrove finch, which is being ravaged by an introduced fly called Philornis downsi.

“In 2013, 37% of mangrove finch nestlings were killed by Philornis downsi,” says conservationist Francesca Cunninghame, of the Charles Darwin Foundation.

“This is a loss which cannot be sustained in a population as reduced as that of the mangrove finch – in the same year, there were only 14 breeding pairs.”

Philornis downsi colonises nests and finds its way into the nasal cavities of fledglings, where it can cause beak deformation and blood loss leading to death.

It was first identified in the 1990s and recent tests indicate that fumigating nests with permethrin, an insecticide which is not harmful to birds, can dramatically improve the health of a brood.

Scientists are also experimenting with captive breeding programmes in an attempt to boost numbers.

“The Galapagos has had zero bird extinctions and we want to keep it that way,” says Dr Parker. “We need to find answers now while the potential exists to do something about it – before Galapagos becomes another Hawaii.”

Charles Darwin to receive apology from the Church of England for rejecting evolution.

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The Church of England is to apologise to Charles Darwin for its initial rejection of his theories, nearly 150 years after he published his most famous work.

The Church of England will concede in a statement that it was over-defensive and over-emotional in dismissing Darwin’s ideas. It will call “anti-evolutionary fervour” an “indictment” on the Church”.

Charles Darwin to receive apology from the Church of England for rejecting evolution

The bold move is certain to dismay sections of the Church that believe in creationism and regard Darwin’s views as directly opposed to traditional Christian teaching.

The apology, which has been written by the Rev Dr Malcolm Brown, the Church’s director of mission and public affairs, says that Christians, in their response to Darwin’s theory of natural selection, repeated the mistakes they made in doubting Galileo’s astronomy in the 17th century.

“The statement will read: Charles Darwin: 200 years from your birth, the Church of England owes you an apology for misunderstanding you and, by getting our first reaction wrong, encouraging others to misunderstand you still. We try to practise the old virtues of ‘faith seeking understanding’ and hope that makes some amends.”

Opposition to evolutionary theories is still “a litmus test of faithfulness” for some Christian movements, the Church will admit. It will say that such attitudes owe much to a fear of perceived threats to Christianity.

Study shows maths experts are ‘made, not born’

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A new study of the brain of a maths supremo supports Darwin’s belief that intellectual excellence is largely due to “zeal and hard work” rather than inherent ability.

University of Sussex took fMRI scans of champion ‘mental calculator‘ Yusnier Viera during arithmetical tasks that were either familiar or unfamiliar to him and found that his did not behave in an extraordinary or unusual way.

The paper, published this week (23 September 2013) in PloS One, provides scientific evidence that some calculation abilities are a matter of practice. Co-author Dr Natasha Sigala says: “This is a message of hope for all of us. Experts are made, not born.”

Cuban-born Yusnier holds world records for being able to name the days of the week for any dates of the past 400 years, giving his answer in less than a second. This is the kind of ability sometimes found in those with autism, although Yusnier is not on the autistic spectrum. Unlike those with autism or the related condition Asperger’s, he is able to explain exactly how he calculates his answers – and even teaches his system and has written books on the subject.

The study, carried out at the Clinical Imaging Sciences Centre on the University of Sussex campus, suggests that Yusnier has honed his ability to create short cuts to his answers by storing information in the middle part of the brain specialised for long-term (the and surrounding cortex). This type of memory helps us carry out tasks in our area of expertise with speed and efficiency.

Although the left side of his brain was activated during – which is normal for all brains – the scientists observed that something slightly different happened when Yusnier was presented with unfamiliar problems.

The scans showed marked connectivity of the anterior (prefrontal cortex), which are involved in decision making, during the unfamiliar calculations. This supports Yusnier’s report that he was building in an extra step to his mental processes to turn an unfamiliar problem into a familiar one. His answers to the unfamiliar questions had an 80 per cent degree of accuracy (compared with more than 90 per cent for familiar questions) and his responses were slightly slower.

https://i0.wp.com/phys.org/newman/gfx/news/2013/studyshowsma.jpg

Dr Sigala explains: “Although this kind of ability is seen among some people with autism, it is much rarer in those not on that spectrum. Brain scans of those with autism tend to show a variety of activity patterns, and autistic people are not able to explain how they reach their answer.

“With Yusnier, however, it is clear that his expertise is a result of long-term practice – and motivation.”

She adds: “It was beyond the scope of our paper to discuss the debate on deliberate practice vs. innate ability. But our study does not provide evidence for specific innate ability for mental calculations. As put by Charles Darwin to Francis Galton: ‘ […] I have always maintained that, excepting fools, men did not differ much in intellect, only in zeal and hard work; I still think this an eminently important difference.'”

There’s Something Special About Islands.

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Islands seem to have it all: ample sunshine, white sand beaches, and species you can’t find anywhere else on Earth. Since Charles Darwin first traveled to the Galapagos Islands and British naturalist Alfred Russel Wallace to the Malay Archipelago in the mid-19th century, ecologists have believed there is something special about islands. A new study provides some of the first empirical evidence that island biodiversity really is different from that of the mainland. The findings have implications not just for how evolution and natural selection operate in these insular areas, but also for how conservation efforts can best protect them.

Darwin and Wallace noted many instances of the uniqueness of islands. For example, when Darwin analyzed bird specimens from the Galapagos after arriving back in England, he noticed that many neighboring islands hosted their own species of finch. Despite this recognition, the so-called theory of island biogeography didn’t take off until the 1960s. Back then, ecologists Robert MacArthur and E.O. Wilson began to study species diversity on islands in an attempt to predict how many kinds of organisms a recently formed island could support. They predicted that islands closest to the mainland would be the least unique and that the islands with the highest biodiversity would have been separate from the mainland for the longest period of time. The notion that islands were ecologically and evolutionarily different from the mainland due to their isolation was mostly uncontested until 2005, when a group of international ecologists published a study in Nature indicating that the number of unique species in mainland areas such as the Amazon basin and central African rainforests rivals that of many islands.

In the new study, Adam Algar, an ecologist at the University of Nottingham in the United Kingdom, and colleagues decided to measure exactly how unique islands were by analyzing their rate of species turnover—a value that compares the number of species present in two different locations. Measuring biodiversity by species richness simply accounts for the number of species in a particular area, whereas species turnover allows scientists to compare the number and identities of species between two places, Algar says.

Algar and colleagues measured species turnover using Anolis lizards and Terrarana frogs, two groups of New World animals that underwent rapid evolutionary change and split into a variety of new species whenever they moved to a new environment. The researchers counted the species of Anolis lizards and Terrarana frogs on different Caribbean islands using published species lists. To get a representative measure of Anolis and Terrarana species turnover in the tropical Central and South American mainland, the team created island-sized, nonoverlapping samples. The researchers randomly oriented and superimposed these island shapes on maps of the Central and South American tropical mainland and identified the species living in each area using the same sources as for the islands. They computed species turnover by calculating the number of Anolis lizard and Terrarana frog species unique to pairs of different areas, and then factoring in variables such as the distance between the two areas and any environmental differences, such as elevation and rainfall.

Species turnover between a mainland sample and an island was much higher, on average, than between two mainland areas or two islands, the team reports online today in the Proceedings of the Royal Society B. A higher level of species turnover on islands indicates that islands had more unique species than similar-sized areas of the mainland. Anolis lizards and Terrarana frogs were more likely to form new species on islands because they were isolated by salt water and couldn’t return to the mainland to breed with other members of their species, the team concludes. This meant that that the species on two islands were more likely to be different from each other than were the species in two mainland samples.

“Islands are unique from mainland areas,” Algar says. “There really is something special about island environments that we hadn’t recognized before.”

The study has limitations, Algar says. For one, he and his colleagues used only two animal genera to measure species turnover. Furthermore, the mainland samples were randomly selected, rather than focusing on areas with high numbers of endemic species (with flora and fauna can only be found in a particular geographic area). Algar is currently planning a follow-up study to compare species turnover between islands and areas of the mainland that have many endemic species.

Besides improving our understanding of how biodiversity evolves on islands, the results could help guide conservation. It’s much easier to preserve species diversity in a representative section of a mainland ecosystem than by preserving one island of an archipelago, Algar says. Because each island has a unique array of plants and animals, conservationists need to protect the entire island chain.

“The study provides additional, comprehensive evidence that islands are important cradles of biodiversity,” Lauren Buckley, a biologist at the University of North Carolina, Chapel Hill, writes in an e-mail. “Species on islands are more unique than would be expected based on environmental differences and geographic separation.”

Source: Science Now.