Evolution, Darwin, Wallace and Patrick Matthew

This video says about itself:

Forsdyke Evolution Academy 01-14 Patrick Matthew

12 October 2011

The second of a series of 12 videos on natural selection from a historical perspective.

From King’s College London in England:

April 20, 2015

The overlooked third man

The horticulturist who came up with the concept of ‘evolution by natural selection‘ 27 years before Charles Darwin did should be more widely acknowledged for his contribution, states a new paper by a King’s College London geneticist.

The paper, published in the Biological Journal of the Linnean Society, argues that Patrick Matthew deserves to be considered alongside Charles Darwin and Alfred Russel Wallace as one of the three originators of the idea of large-scale evolution by .

Furthermore, Matthew’s version of evolution by natural section captures a valuable aspect of the theory that isn’t so clear in Darwin‘s version – namely, that natural selection is a deductive certainty more akin to a ‘law’ than a hypothesis or theory to be tested.

Patrick Matthew (1790-1874) was a Scottish landowner with a keen interest in politics and agronomy. He established extensive orchards of apples and pears on his estate at Gourdie Hill, Perthshire, and became adept in horticulture, silviculture and agriculture.

Whilst Darwin and Wallace‘s 1858 paper to the Linnean Society, On the Origin of Species, secured their place in the history books, Matthew had set out similar ideas 27 years earlier in his book On Naval Timber and Arboriculture. The book, published in 1831, addressed best practices for the cultivation of trees for shipbuilding, but also expanded on his concept of natural selection.

“There is a law universal in nature, tending to render every reproductive being the best possibly suited to its condition that its kind, or that organized matter, is susceptible of, which appears intended to model the physical and mental or instinctive powers, to their highest perfection, and to continue them so. This law sustains the lion in his strength, the hare in her swiftness, and the fox in his wiles.” (Matthew, 1831: 364)

In 1860, Matthew wrote to point out the parallels with his prior work, several months after the publication of On the origin of species. Darwin publically wrote in 1860 “I freely acknowledge that Mr. Matthew has anticipated by many years the explanation which I have offered of the origin of species”, while Wallace wrote publically in 1879 of “how fully and clearly Mr. Matthew apprehended the theory of natural selection, as well as the existence of more obscure laws of evolution, many years in advance of Mr. Darwin and myself”, and further declared Matthew to be “one of the most original thinkers of the first half of the 19th century”. However, both asserted their formulations were independent of Matthew’s.

Even if Matthew did not influence Darwin and Wallace, his writings provide a valuable third point of reference on the notion of macroevolution by natural selection, argues the paper’s author, Dr Michael Weale. Dr Weale has created a public website to act as an online repository of the writings by Patrick Matthew, including some of his lesser-known work.

Dr Michael Weale, from the Department of Medical and Molecular Genetics at King’s College London, said: ‘Whilst Darwin and Wallace both deserve recognition for their work, Matthew, the outsider who deduced his idea as part of a grand scheme of a purposeful universe, is the overlooked third man in the story. Matthew’s story is an object lesson in the perils of low-impact publishing. Despite its brevity, and to some extent because of it, Matthew’s work merits our renewed attention.’

Explore further: Darwin’s finches highlight the unity of all life

More information: ‘Patrick Matthew’s Law of Natural Selection’ by Michael Weale is published in the Biological Journal of the Linnean Society and can be accessed here.

From Wikipedia:

Matthew’s idea on society were radical for their times. Although he was a landowner, he was involved with the Chartist movement, and argued that institutions of “hereditary nobility” were detrimental to society. It has been suggested that these views worked against acceptance of his theory of natural selection, being politically incorrect at the time (see Barker, 2001).

Fossils collected by Charles Darwin: here.


Galapagos finches and Charles Darwin

This video says about itself:

Galapagos Finch Evolution — HHMI BioInteractive Video

26 August 2014

The Galápagos finches remain one of our world’s greatest examples of adaptive radiation. Watch as evolutionary biologists Rosemary and Peter Grant detail their 40-year project to painstakingly document the evolution of these famous finches. Their pioneering studies have revealed clues as to how 13 distinct finch species arose from a single ancestral population that migrated to the islands 2 million to 3 million years ago.

Use this video as a supplementary resource for lesson plans centered on teaching evolution. The video expertly illustrates the effects of natural selection on Galápagos finch populations.

Free classroom resources supporting this short film can be found here.

By Frank Nicholas, The Conversation:

April 3, 2015

Darwin’s finches highlight the unity of all life

When Charles Darwin visited the Galapagos Islands in October 1835, he and his ship-mates on board HMS Beagle collected specimens of birds, including finches and mockingbirds, from various islands of the archipelago.

At the time, Darwin took little interest in the quaint , making only a one-word mention of them in his diary. As painstakingly shown by Frank Sulloway and more recently by John Van Whye, it wasn’t until two years later that the finches sparked Darwin’s interest.

By then he had received feedback from the leading taxonomist of the time, John Gould, that the samples comprised 14 distinct species, none of which had been previously described! Gould also noted that their “principal peculiarity consisted in the bill [i.e. beak] presenting several distinct modifications of form”.

So intrigued was Darwin by this variation in size and shape of beaks that in the second (1845) edition of Journal of Researches he included illustrations of the distinctive variation between species in the size and shape of their beaks. He added a comment that:

Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.

Unfortunately for Darwin, the closer he examined the available evidence on Galapagos finches, the more confusing the picture became. This was partly because the specimens available to him were not sufficiently labelled as to their island of collection.

Presumably, it was his doubt about the available evidence that resulted in Darwin making no mention of Galapagos finches in any edition of Origin of Species.

Why, then, do people now label them as “Darwin’s finches”, and why are these finches now regarded as a classical textbook example of his theory of evolution by natural selection?

Paragons of evolution

Despite not mentioning Galapagos finches, Darwin did make much use of evidence from other Galapagos species (especially mockingbirds) in Origin of Species.

As the influence of Origin of Species spread, so too did the evolutionary fame of the Galapagos Islands. Increasingly, other biologists were drawn into resolving the questions about finches that Darwin had left unanswered.

By the end of the 19th century, Galapagos finches were among the most studied of all birds. By the mid-20th century, there was abundant evidence that Galapagos finches had evolved to fill the range of ecological niches available in the archipelago – a classic example of evolution by adaptive radiation.

Beak size and shape were key attributes in determining adaptation to the different types of food available. In the second half of the 20th century, classic research by Princeton University’s Peter and Rosemary Grant provided evidence of quite strong natural selection on beak size and shape.

Under the hood

New light has also been shed on the evolution of Darwin’s finches in a paper recently published in Nature. In this latest research, the entire genomes of 120 individual birds from all Galapagos species plus two closely related species from other genera were sequenced.

The work was done by a team led by Swedish geneticist Leif Andersson, with major input from Peter and Rosemary Grant, who are still leading experts on the finches.

Comparison of sequence data enabled them to construct a comprehensive evolutionary tree based on variation across the entire finch genome. This has resulted in a revised taxonomy, increasing the number of species to 18.

The most striking feature of the genome-based tree is the evidence for matings between different populations, resulting in the occasional joining of two branches of the tree. This evidence of “horizontal” gene flow is consistent with field data on matings of finches gathered by the Grants.

A comparison of whole-genome sequence between two closely related groups of finches with contrasting beak shape (blunt versus pointed) identified at least 15 regions of chromosomes where the groups differ substantially in sequence.

Unity of life

The most striking difference between the two groups was observed in a chromosomal region containing a regulatory gene called ALX1. This gene encodes a peptide that switches other genes on and off by binding to their regulatory sequences.

Like other such genes, ALX1 is crucially involved in embryonic development. Indeed, mutations in ALX1 in humans and mice give rise to abnormal development of the head and face.

It is an extraordinary illustration of the underlying unity of all life on Earth that Leif Andersson and his colleagues have shown that the ALX1 gene also has a major effect on beak shape in finches, and that this gene has been subject to natural selection during the evolution of the Galapagos finches.

If Darwin were alive today, he would be astounded at the power of genomics tools such as those used in generating the results described in this paper. He would also be delighted to see such strong evidence not only in support of evolution but also in support of one of its major forces, .

The evolution of birds on the Galapagos Islands, the cradle of Darwin’s theory of evolution, is a two-speed process. Most bird species are still diversifying, while the famous Darwin’s finches have already reached an equilibrium, in which new species can only appear when an existing one becomes extinct. This finding expands the classical theory on island evolution put forward in the 1960s: here.

Flowering plants evolution and Charles Darwin

This video is called Blooming flowers, amazing nature!

From the BBC:

The abominable mystery: How flowers conquered the world

Charles Darwin was baffled by the speed with which flowers evolved and spread. Now genetics could solve the mystery

It was, Charles Darwin wrote in 1879, “an abominable mystery”. Elsewhere he described it as “a most perplexing phenomenon”. Twenty years after the publication of his seminal work The Origin of Species, there were still aspects of evolution that bothered the father of evolutionary biology. Chief among these was the flower problem.

Flowering plants from gardenias to grasses, water lilies to wheat belong to a large and diverse group called the angiosperms. Unlike almost all other types of plants, they produce fruits that contain seeds. What worried Darwin was that the very earliest samples in the fossil record all dated back to the middle of the Cretaceous period, around 100 million years ago, and they came in a bewilderingly wide variety of shapes and sizes. This suggested flowering plants had experienced an explosive burst of diversity very shortly after their origins – which, if true, threatened to undermine Darwin’s entire model of gradual evolution through natural selection.

In fact recently published research has revealed that angiosperms evolved relatively gradually after all. Yet this still leaves a number of key questions. The roughly 350,000 known species of flowering plants make up about 90% of all living plant species. Without them, we would have none of our major crops including those used to feed livestock, and one of the most important carbon sinks that mop up our carbon dioxide emissions would be missing. How and where did they originate? And, perhaps more importantly, why did they become so spectacularly successful?

This 2012 video is about research into the origins of flowering plants.

Darwin was an undoubted expert on origins. His remarkable insights helped establish a framework for the way new species form – and he was adamant that the process was slow and gradual.

“As natural selection acts solely by accumulating slight, successive, favourable variations, it can produce no great or sudden modification; it can act only by very short and slow steps,” he wrote in The Origin of Species.

But Darwin was painfully aware that there were apparent exceptions to his slow and steady rule. The angiosperms were a particular source of frustration. Angiosperms simply didn’t exist for most of Earth’s history. Early forests were populated by bizarre primitive tree-like plants closely related to the club mosses and horsetails that are a very minor part of today’s plant communities. Later a group called the gymnosperms – plants with unenclosed seeds such as the conifers – took over. And then came the angiosperms.

Early in the 19th century, scientists like Adolphe-Théodore Brongniart began collating everything that was then known about fossil plants. Work like this highlighted the fact that a huge variety of angiosperms – often called the “higher plants” or dicotyledons in the 19th century – popped up all too suddenly in the middle of the Cretaceous geological period.

“[The] sudden appearance of so many Dicotyledons… appears to me a most perplexing phenomenon to all who believe in any form of evolution, especially to those who believe in extremely gradual evolution,” Darwin wrote to Swiss naturalist Oswald Heer in 1875.

He was well aware the sudden appearance of flowering plants was more than just perplexing. It also provided his critics with ammunition against his evolutionary model.

Darwin did suggest a solution, however. Angiosperms, he said, may have evolved gradually in a remote region of the world as yet unexplored by scientists. By the middle of the Cretaceous, something caused them to spill out of their homeland and rapidly spread across the world. This, reasoned Darwin, would give the misleading impression to researchers working in Europe and North America that a wide variety of flowering plant species had all evolved at the same time. Aware of the lack of evidence to back up his theory, Darwin described it as “wretchedly poor”.

In fact, his speculation has since proved to be partly correct. Angiosperms that predate the middle Cretaceous specimens by tens of millions of years have begun to turn up in rocks from China. But Darwin didn’t get the details entirely right because very rare early angiosperms have been found in Europe and the US too.

“Our knowledge has greatly increased since the end of the 19th century,” says Laurent Augusto at the National Institute for Agricultural Research in Bordeaux, France. Palaeobotanists may not yet agree on precisely where and when flowering plants first evolved, but their appearance in the fossil record much earlier than was previously known means they are no longer a problem for Darwin’s theory of gradual evolution. Other debates about them, especially concerning their spectacular diversity, remain active, however.

“Our world is an angiosperm world,” says Augusto. “In many ecosystems they dominate in species and in biomass – this angiosperm ecological dominance remains unexplained.”

This video from the USA is called Floral Beaks and Flower Evolution.

Clues to the ultimate origins of flowering plants are to be found on New Caledonia, a small island about 1,600 kilometres east of Australia. Here, around the time that Darwin was agonising over his angiosperm problem, botanists discovered a plant called Amborella. Careful study over the last century has shown it to be the sole survivor of one of the very earliest branches of the angiosperm evolutionary tree. This means its relationship to all living flowers is bit like that of the duck-billed platypus to all living mammals: it might look unassuming, but Amborella can tell us more than even the most elaborate orchid about how the angiosperms first evolved.

Last year, the plant finally spilled some of its secrets. The Amborella Genome Project unveiled a draft version of the plant’s genome. The first angiosperms must have evolved from one of the gymnosperm species that dominated the world at the time. The Amborella genome suggests that the first angiosperms probably appeared when the ancestral gymnosperm underwent a ‘whole genome doubling‘ event about 200 million years ago.

Genome doubling occurs when an organism mistakenly gains an extra copy of every one of its genes during the cell division that occurs as part of sexual reproduction. The extra genetic material gives genome doubled organisms the potential to evolve new traits that can provide a competitive advantage. In the case of the earliest angiosperms, the additional genetic material gave the plants the potential to evolve new, never-before-seen structures – like flowers. The world’s flora would never be the same again.

The Amborella genome results strongly suggest that flowers have been a defining feature of the angiosperms from very early on in their evolution. Could the flowers themselves help explain why the angiosperms became so diverse?

Darwin was certainly open to the possibility. While he was wrestling with the problem posed by the seemingly sudden appearance of the angiosperms, he received a letter from Gaston de Saporta, a French biologist who said the apparent evidence of the 19th century fossil record suggesting the plant group appeared suddenly need not be a problem for Darwin’s theory of gradual evolution. It simply showed that angiosperms were an unusual exception to his general rule. Flowering plants and their insect pollinators evolved together, reasoned Saporta, and this ‘co-evolution’ drove both groups to diversify unusually rapidly.

“Your idea … seems to me a splendid one,” responded an enthusiastic Darwin. “I am surprised that the idea never occurred to me, but this is always the case when one first hears a new and simple explanation of some mysterious phenomenon.”

But the theory runs into trouble today, says Augusto. Early angiosperms may have had flowers, but we now know from fossils that those first flowers were very plain – and probably not that attractive to pollinators. By the time the big, bold flowers that entice insects appeared, the angiosperms were already diverse.

Another theory, advanced by Frank Berendse and Marten Scheffer at Wageningen University in the Netherlands in 2009, rests on the fact that the angiosperms are much more productive than gymnosperms like the conifers. Perhaps they simply outcompeted rival plants by growing faster and gobbling up the lion’s share of the nutrients, they suggested.

“Our paper was meant to be a bit provocative,” says Berendse, to encourage botanists and those who study fossil plants to work together more closely on explaining the spectacular rise of the angiosperms.

In fact, the two had already begun working together. Earlier in 2009, a team led by Tim Brodribb at the University of Tasmania in Hobart, Australia, published the first in a series of papers exploring angiosperm evolution by examining fossil leaves. They found that their leaves gained many more veins during the Cretaceous, which would have provided them with more water for photosynthesis, and allowed them to grow more rapidly.

“That provided very strong support for our ideas,” says Berendse. But as with the flower hypothesis, problems remain with the nutrient-based theory. For instance, while individual angiosperm leaves are more efficient at photosynthesising than conifer needles, conifers may be able to compensate because their needles collectively have a much larger surface area than that of the leaves of an average angiosperm tree.

Unfortunately, there are no simple explanations for the diversity and ecological dominance of the flowering plants. “Very probably no single theory can explain the massive rise of the angiosperms,” admits Berendse.

It’s more likely, says Augusto, that several factors played a role, with each being more or less important in specific places and times. For instance, Berendse’s productivity theory may apply in the tropical belts, where rich soils could give nutrient-hungry angiosperms a vital edge over gymnosperms, but it might not explain what’s going on in regions with poor soils, where angiosperms are potentially starved of the nutrients they need. And the simple flowers of early angiosperms may have done little for the evolution of the group, but when elaborate flowers finally appeared they probably did help drive the plant group to take over the world.

That is, if they really did take over the world. It might seem odd to suggest otherwise when there are something like 350,000 known angiosperm species and not many more than 1000 gymnosperms, most of which are conifers. But there’s more to success than diversity, says Brodribb. Many of the few conifers species that do survive are super-abundant.

“In the northern hemisphere conifers rule the vast boreal and much of the temperate zone,” says Brodribb. He adds that the angiosperms have not become ecologically dominant in many of these regions. This might be because the soils there are too poor for them to establish a nutritional advantage, in keeping with Berendse’s ideas, or perhaps it’s because temperatures drop too low for them to survive. But why even in 350,000 attempts the angiosperms haven’t come up with species that can overcome these problems and outcompete those northern conifers is another unsolved mystery.

Today’s plant scientists understandably have a better handle on the origins of flowering plants than Darwin did, but they are still struggling to explain the group’s diversity, and why despite this it has failed to become dominant in some parts of the world.

Augusto, at least, is confident that answers will eventually be found, in part because these mysteries continue to fascinate researchers. And while there is little doubt this fascination stems in part from the ecological and economic importance of angiosperms today, perhaps it is also partly down to Darwin and his way with words. “I think the ‘abominable mystery’ quote does contribute to the general interest in angiosperms,” adds Augusto.

One of the main types of fossil used to understand the first flowering plants (angiosperms) are charred flowers. These charcoals were produced in ancient wildfires, and they provide some evidence for the types of plants that grew millions of years ago. However, when fires burn they not only produce charcoal, but they also destroy it: here.

Charles Darwin’s complete Galapagos library posted online

This video says about itself:

11 November 2011

A classic example of evolution on Daphne Major Island in the Galapagos. Natural selection works on beak size variation of Darwin’s Finches.

From ars technica:

Darwin’s complete Galapagos library posted online

404 volumes kept on board the Beagle join the giant Darwin Online repository.

by Sam Machkovech – July 16 2014, 10:40pm +0200

Charles Darwin‘s massive ship library, including astounding drawings of species from far-off lands, meant he rarely had to come above-board while sailing on the Beagle in the 1830s.

Charles Darwin’s five-year journey to and from the Galapagos Islands ended in 1836. While that was over two decades before the publication of On the Origin of Species, he credited his time on board the Beagle as a formative experience for his theory of evolution. That extended trip wasn’t only spent studying local wildlife, especially during lengthy voyages at sea to and from home—Darwin also devoured a library of more than 400 volumes of text.

While many of those books were referenced in his later research, they were not preserved as a collection once the Beagle returned to England, leaving a gap in our understanding about the books and studies that kept Darwin’s mind occupied during such an historic era. Now, thanks to the painstaking efforts of a two-year Beagle project funded by the government of Singapore, that complete on-ship library has been transcribed and posted at Darwin Online, the world’s largest repository of Darwin-related texts and writings.

The library, which was stored in the same cabin as Darwin’s bed and desk during his journey, totaled out at 195,000 pages by the time researchers at the National University of Singapore assembled the full collection (and these weren’t exactly picture books, with only 5,000 corresponding illustrations). The complete list is quite astounding, made up of atlases, history books, geology studies, and even a giant supply of literature. Darwin also enjoyed a few books in French, Spanish, and German, along with a book in Latin about species and a Greek edition of the New Testament.

Historians and fans can read and perform text searches of the fully transcribed library. But if you’re pressed for time, we strongly encourage you to at least skim through the collection of gorgeous illustrations.

American tanagers’ colours and songs, new study

This video is called Colombia Tanagers [various species].

From Wildlife Extra:

Study dispels Darwin’s theory to prove birds can have it all

Despite popular belief birds can have a brilliant plumage, a virtuosic singing chirp and an intricate dance routine say scientists.

The author of a new study, Nick Mason, from the the Cornell Lab of Ornithology in New York state, challenged the long-held notion, first proposed by Charles Darwin, that for a bird species to excel in one area it must give up its edge in another.

For example, male northern cardinals are a dazzling scarlet, but sing a fairly simple whistle, whereas the dull brown House Wren sings one of the most complicated songs in nature.

Mason and his colleagues tested the theory by examining a very large family of songbirds from Central and South America, the tanagers.

This group consists of 371 species and included some of the most spectacularly colourful birds in the world such as the paradise tanager as well as the more drab birds, such the black-bellied seedeater. The group also includes both accomplished and weak songsters alike.

“If there were going to be any group of birds at all that would show this trade-off, the tanagers would be a very good candidate, because there’s all this variation in song and plumage complexity,” Mason said.

“But when we dived into it and did some rigorous statistics, it turns out that there is no overall trend. Tanagers can be drab and plain-sounding, or colourful and musical, or or anything in between.”

It’s still possible that trade-offs take place at the level of genus, Mason said, or that they influence species relatively fleetingly as evolutionary pressures appear and disappear.

But as a broad effect on an entire family of birds, a voice–plumage trade off doesn’t seem to exist. One possibility is that the resources needed to develop fancy plumage are different from the ones required for complex songs, freeing tanagers to invest in both forms of showiness simultaneously.

USA: Seeing the vivid red bodies and black wings of male Scarlet Tanagers is a sure sign spring has arrived: here.

Darwin’s childhood garden now Wildlife Trust property

This video from England is called Visit Charles Darwin‘s Shrewsbury, the birthplace of evolution!

From Wildlife Extra:

Darwin’s garden purchased

January 2014: A wooden remnant of naturalist Charles Darwin’s childhood garden in Shrewsbury, Shropshire has been bought by Shropshire Wildlife Trust.

“No other part of Darwin’s childhood home is accessible to the public, so when we were offered the chance to buy this slip of woodland next to the river, we were thrilled at the opportunity to open up a cherished corner of his world,” said Colin Preston, Director of Shropshire Wildlife Trust.

While much of the land previously attached to The Mount, his birthplace, has disappeared under housing, other parts survived in private gardens, including the land the Trust has bought.

Through the wood, alongside an ice house once used by the Darwins, runs a path with views down to the River Severn. It was here 200 years ago, that the young Darwin was sent every day before breakfast to walk the path at the bottom of the garden. It was known as the Thinking Path and provided a regular time for thought and reflection. The habit became ingrained in Darwin’s daily routine and when he and his wife Emma bought Down House in Kent, they made their own Sandwalk through the grounds, carrying on the tradition of morning walks with their children.

The Trust intends to restore the Thinking Path, open up views and carry out essential boundary and safety work. The garden will be opened for group visits at various times throughout the year and schoolchildren will have the chance to walk in Darwin’s footsteps, inspiring them to enjoy and explore the natural world.

Enhanced by Zemanta

Island lizards less scared of people

This video is called Marine iguanas of the Galapagos islandsBBC wildlife.

From Nature:

Islands make animals tamer

Lizard study supports Darwin‘s hunch that lack of predators leads to unwatchful behaviour.

Ed Yong

08 January 2014

When Charles Darwin visited the Galapagos Islands, he noted that many of its animal inhabitants were so unafraid of people that “a gun is here almost superfluous”. He swatted birds with his hat, pulled the tails of iguanas and sat on giant tortoises.

These antics fuelled his famous idea that animals become tame when they live on remote, predator-free islands. Now, William Cooper Jr of Indiana University–Purdue University in Fort Wayne has tested Darwin’s hypothesis on 66 species of lizards from around the world and found that island dwellers tended to be more docile than their continental relatives — the strongest evidence yet for this classic idea. The results are published this week in Proceedings of the Royal Society B1.

Several studies and unpublished reports have shown that particular species are more approachable on islands where there are fewer predators, or quicker to flee on islands that contain introduced hunters such as feral cats. But despite this largely anecdotal evidence for island tameness, “no one has ever established that it’s a general phenomenon in any group”, says Cooper. “We showed that for a large prey group — lizards — there really is a significant decline in wariness on islands.”

Taming of the few

Island tameness is an old idea, but there have been few tests of it,” says Dan Blumstein, a behavioural biologist at the University of California, Los Angeles. “This is a needed paper that convincingly shows some of the drivers of island tameness in lizards.”

Cooper and his colleagues scoured past studies and collated data on the distance at which lizards start to flee when approached by a researcher. They took a conservative approach, discarding studies in which researchers had pointed at the lizards, walked towards the animals faster or slower than a particular fixed speed, or studied populations that were habituated to humans.

Cooper and his team ended up with data for 66 species, from the Eurasian common lizard (Zootoca vivipara) to the Galapagos marine iguana (Amblyrhynchus cristatus). The results clearly showed that humans can get closer to island-dwelling lizards than to mainland ones, and that lizards become more approachable on islands that are farther from the mainland.

Island ecology is so important that it overrides any effect of evolutionary history, Cooper and his co-authors say. They also showed that even closely related lizard species have different escape behaviours depending on where they live, and that their evolutionary relationships were mostly irrelevant.

The results do not explain why island lizards are tamer than those on the mainland, although the relative lack of island predators is the most likely reason. Animals with skittish dispositions can needlessly abandon valuable resources, and natural selection would be expected to weed out such responses if predators are rare or absent.

Cooper wants to test this idea, but says that it is hard to get decent data on the numbers, densities and types of predators on different islands.

See also here. And here.

Enhanced by Zemanta