The New York Times reports that monarch butterflies migrating from North America to central Mexico appear to be doing better than last year, when the over-wintering colony occupied just 1.7 acres. This year’s survey finds the butterflies have filled 2.8 acres, which seems like a solid improvement until you consider that the peak colony size, since record-keeping started, was 44.5 acres.
(Incidentally, 44.5 acres is more than 40 American football fields of forest covered with roosting monarch butterflies.)
The monarchs that migrate to Mexico aren’t the only population — there’s another migratory route on the U.S. Pacific coast, and there are non-migratory populations in Florida, Hawaii, and even New Zealand. But the Mexico overwintering site represents what used to be the single largest monarch population, butterflies that spend summer across most of North America east of the Rocky Mountains. Logging in Mexico and the loss of summer habitat to farming in the Midwest has been hitting the butterflies hard for years, and while this rebound is encouraging, it might still make sense to put the monarch on the Endangered Species List, as the U.S. Fish and Wildlife Service is considering.
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.
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.
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”
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.
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.
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,
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.