Tag: evolution

Top 100 Stories of 2009

Discover magazine listed our PNAS article as #30 on its list of top 100 science stories of 2009.

Humans are powerful agents of evolutionary change: Wild animals and plants that are hunted or harvested evolve three times as quickly as they would naturally, according to a study from the University of California at Santa Cruz. In our quest to bag the biggest and the best, we introduce selective pressures that favor less desirable creatures, such as those with smaller bodies or less majestic horns. Hunting also gives a competitive advantage to animals that have babies when they are younger, before they become tempting targets for humans.

A team led by biologist Chris Darimont combed through data on dozens of species—predominantly fish but also bighorn sheep, caribou, marine invertebrates, and two plants. (“Hunters also want the biggest ginseng,” Darimont says.) Animals that are routinely subject to pursuit are, on average, 20 percent smaller and reproduce at a 25 percent younger age than what would be expected without human influence, the researchers determined. Predation is not the only way that people affect populations. Creatures that are exposed to environmental influences like pollution also experience accelerated evolution, although the effect is less dramatic.

The resulting changes have ripple effects, Darimont notes. Smaller and earlier breeders often produce fewer offspring, for instance. “Size really matters,” he says. “If a harvested animal keeps shrinking, it may no longer be prey to its predator. The whole food web can be altered.”

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Human-Driven Evolution

From Science Friday on NPR, Chris Darimont discusses our recent PNAS paper on human-driven evolution.  Listen to the full radio spot here.

Can humans angling for the prize-winning fish shift the course of evolution? Research published this week in the Proceedings of the National Academy of Sciences says that predation by humans through hunting, fishing, and gathering has had significant influences on the rate of evolutionary change in a wide variety of species. Traits such as body size and first reproductive age shift significantly in species that are ‘harvested,’ the authors say.

“Fishing regulations often prescribe the taking of larger fish, and the same often applies to hunting regulations,” said Chris Darimont, one of the authors of the study. “Hunters are instructed not to take smaller animals or those with smaller horns. This is counter to patterns of natural predation, and now we’re seeing the consequences of this management.” Darimont and colleagues found that human predation accelerated the rate of observable trait changes in a species by 300 percent above the pace observed within purely natural systems, and 50 percent above that of systems subject to other human influences, such as pollution,. We’ll talk with Darimont about the team’s findings.

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Research Ties Human Acts to Harmful Rates of Species Evolution

From the NY Times, a Science Times article on our recent PNAS paper.

Human actions are increasing the rate of evolutionary change in plants and animals in ways that may hurt their long-term prospects for survival, scientists are reporting.

Hunting, commercial fishing and some conservation regulations, like minimum size limits on fish, may all work against species health.

The idea that target species evolve in response to predation is not new. For example, researchers reported several years ago that after decades of heavy fishing, Atlantic cod had evolved to reproduce at younger ages and smaller sizes.

The new findings are more sweeping. Based on an analysis of earlier studies of 29 species — mostly fish, but also a few animals and plants like bighorn sheep and ginseng — researchers from several Canadian and American universities found that rates of evolutionary change were three times higher in species subject to “harvest selection” than in other species. Writing in The Proceedings of the National Academy of Sciences, the researchers saythe data they analyzed suggested that size at reproductive maturity in the species under pressure had shrunk in 30 years or so by 20 percent, and that organisms were reaching reproductive age about 25 percent sooner.

Click here to read the full article at nytimes.com.

 

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The Fastest Way to Change a Species: Start Eating It

From Science magazine, more coverage on our PNAS article.

From the dwindling Atlantic cod to the increasingly rare American ginseng plant, species are racing to adjust to relentless human exploitation. According to a new analysis, the rate at which hunted and harvested species are changing their size and breeding schedules is unmatched in natural systems. Ecologists say the results point to errors in the way we manage fisheries and other harvested populations.

Researchers have noted rapid changes in heavily exploited fish and other species since the 1970s. To name one famous example, adult Atlantic cod (Gadus morhua) have decreased 20% in size over the past 30 years, and females now reproduce a year earlier than they used to (ScienceNOW, 31 January 2007). Although such hunting-induced alterations seem rapid, evolutionary biologist Chris Darimont of the University of Victoria in Canada, and colleagues wanted to determine whether they outpace changes in nonharvested organisms.

Read the full article here.

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