Under selection, an endangered species runs low on evolutionary “fuel”

Atlapetes pallidiceps

A pale-headed brushfinch, Atlapetes pallidiceps. (Wikimedia Commons:Aves y Conservación/NBII Image Gallery)

The pale-headed brushfinch, Atlapetes pallidiceps, is a conservation success story, or at least the first chapter of one. The birds were thought to be extinct, until a 1998 survey [PDF] of Ecuador’s Yunguilla Valley found four nesting pairs, and observed them foraging for insects and fruit. Following that rediscovery, the Fundacion Jocotoco secured a reserve encompassing the brush finches’ known territory, and took steps to control brood-parasitic cowbirds that were threatening them. Now, the population is five times bigger, with as many as 200 of the birds living in the reserve.

Have the brush finches’ rebounded enough to secure their population for the future? Populations that decline so precipitously can lose genetic variation, and may not regain it even if their numbers increase again. With reduced genetic variation, species that have undergone such a “population bottleneck” event may be unable to respond to natural selection imposed by disease or changing environments.

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Bringing back the “king” of American forests

The American chestnut used to be one of the most common trees in North American hardwood forests, providing enormous crops of nuts that supported birds and other wildlife, and a source of robust, rot-resistant lumber for human use. But American chestnuts were nearly wiped out by the introduction of a virulent chestnut blight from Asia.

But now, after years of selective breeding and some careful genetic engineering, biologists at the State University of New York and the American Chestnut Foundation have produced blight-resistant chestnuts and they’re getting ready to start restoring the population with a crowd-funding campaign. If American chestnuts couldn’t evolve to cope with blight on their own, they may be one of the first species to get an evolutionary helping hand from humans.

Thanks, Bush and Obama!

President Obama is expanding the Pacific Remote Islands Marine National Monument today from the wonderful 86,888 square miles President George W. Bush set up in 2009, to about 490,000 square miles. I gotta love anything involving ocean conservation. Thanks, Bush and Obama!

“This is a great moment,” said Greg Stone, chief scientist for Conservation International. “This is some of the last real tropical ocean wilderness left on the planet, so it’s good put some of these kind of reef systems aside. On top of that there are the protections for the open ocean and I’m assuming for the sea floor from mining,” he said.

From the Guardian article: “Tarawa atoll. Photograph: Richard Vogel/AP”

To thrive in the twenty-first century, can we learn to steer evolution?

Cliff Swallow in flight

Cliff swallow in flight. (Flickr: Don DeBold)

Many of the biggest challenges humanity faces in the next hundred years are biological: dwindling wild lands and disappearing biodiversity, antibiotic-resistant bacteria, and emerging new viruses, but also feeding nine billion people or more a healthy diet in a climate-changed world. As Theodosius Dobzhansky famously remarked—and as this very website’s name proclaims—nothing in biology makes sense except in the light of evolution. So are there evolutionary answers to all these biological challenges? According to a big new review article just released online ahead of print in the journal Science, the answer is emphatically yes.

The long list of authors, led by Scott P. Carroll and including Ford Denison, whose lab is just down the hall from my office at the University of Minnesota, explicitly connect evolutionary principles to global goals for sustainable development. These include the reduction of both “chronic lifestyle” diseases and infectious diseases, establishment of food and water security, clean energy, and maintenance of healthy ecosystems. Carroll and his coauthors divide the applications of evolution to these problems into cases where evolution is the problem, and those where evolution may offer the solution.

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“One of the great migration stories of the world” – Shrimp in the mighty Mississippi.

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Macrobrachium ohione, by Clinton and Charles Robertson, via Flickr.

The Mississippi River that we know today is a creation of the army corps of engineers. Before they got to levying, dredging and damming it into submission, it was a wild and meandering thing that harbored great concentrations of wildlife. One component of that was a massively abundant shrimp with an amazing life cycle:

It turned out that in pre-colonial times the shrimp traveled all the way north into the upper reaches of the Mississippi’s main eastern tributary, the Ohio River, and back again – a 2,000-mile round trip. It was a journey more amazing than similarly epic migrators like salmon. For whereas adult salmon may have an equally long journey to their upstream spawning sites, it is the quarter-inch juvenile shrimp that swim and crawl 1,000 miles upstream against the strong currents of the Mississippi.

What happened to these shrimp? Go read the story to find out.

Living at the edge, range expansion is a losing battle with mutations

Environments can vary substantially in habitat quality, local population abundance, or carrying capacity. Under some climate change scenarios, new, higher quality habitats become available along the margin of a species’ range (e.g. higher latitudes or altitudes) (Thomas et al 2001). These new habitats may be able to support larger population sizes. Factors of demography, evolution, and qualities of the abiotic and biotic communities all interact to determine where a species is found and may influence the ability of a species to expand its range. New research is building genetically explicit models in order to understand how the interplay of these different factors influence evolutionary changes,

Wordle of Peischl et al 2013

The authors of a recent study focus on how the interaction of the demographic process of range expansion changes the way that natural selection favors beneficial and deleterious mutations (Peischl et al 2013). Using both computer simulations as well as mathematical approximations, the authors find that at the range margins, individuals carry a substantial load of deleterious mutations.

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Science denial is…rational?

I, until very recently, believed that there were two types of people in this world – those who accept the theory of evolution and those who do not understand the theory of evolution. In my mind, it was impossible to be presented with the overwhelming evidence for and beautiful simplicity of The Theory and not be convinced. Yet, a small, informal survey of sophomore-ish biology majors here at LSU revealed only 35% responded with “Evolution” to the question: What are your feelings/beliefs about how we, as humans, came to exist on Earth? To be fair, the highest category was “Some mix of evolution, creationism and intelligent design”, which really means only 23% of respondents did not include evolution. These numbers are much better than our national average: Miller et al. (2006) conducted a multinational survey that showed nearly 40% of Americans deem evolution “false”. This makes us second from the bottom (out of 34 countries!) in acceptance of evolution – right below Cyprus and above Turkey.

Small informal survey of undergraduate science majors.

As it turns out, I have overlooked a third type of person: a person who can be exposed to a well-supported argument for an uncontroversial scientific consensus and reject it. These people are a major source of science denial. Rosenau (2012) published an amazing and concise review this week in Trends in Microbiology that discusses science denialism and how it’s more about identity and social groups than scientific facts.

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