Tag Archives: evolution

Vegetarian spider also a smarty pants

Female Bagheera kiplingi

Adult female Bagheera kiplingi eats Beltian body harvested from ant-acacia Photo/R.L. Curry

For ages, ants have had a monopoly on the coveted acacia, protecting the plant from would-be predators in exchange for shelter and food, or so they thought. Skulking in the background, and recently discovered, is an unlikely competitor of the ant — a spider. And this is no ordinary arachnid. The Bagheera kiplingi also happens to be a vegetarian, and is the first of its kind known to science.

“This is really the first spider known to specifically ‘hunt’ plants,” said Christopher Meehan of Villanova University. “It is also the first known to go after plants as a primary food source.”

The veggie-loving tendency of this jumping spider was first discovered in Central America back in 2001 by Eric Olson of Brandeis University. Since then he has teamed up with Meehan, who independently observed the jumping spider in 2007, to learn more about this unusual creature and the extent to which it likes plants. Not only is Bagheera kiplingi the only predominant vegetarian of 40,000 known spider species with plants making up more than 90 percent of its diet, but it’s showing scientists a complex side of arachnid biology and behavior that indicates the spider’s diet is just the beginning of this animal’s surprising life history.

Bagheera defense

Adult female Bagheera kiplingi defends her nest against acacia-ant worker. Photo/R.L. Curry

Ants are aggressive defenders of the acacia plant making life difficult for outsiders who attempt to encroach on their turf. After all, they want those yummy beltian bodies all to themselves. So how is the jumping spider managing to exploit the acacia for both food and shelter?

Science is still trying to figure that out, but preliminary research shows the spiders take advantage of the invertebrate equivalent of run-down real estate, setting up residence in less-than-desirable regions of the acacia. But their ingenuity doesn’t stop there. Bagheera kiplingi are outsmarting their ant foes, said Meehan, exploiting their intelligence and agility to get around the ants. “Individuals employ diverse, situation-specific strategies to evade ants, and the ants simply cannot catch them,” he said.

As if to add insult to co-evolution, the ants may not even know when spiders are in their midst. Bagheera kiplingi literally dupes the ant by baring young that look like carbon-copies of the ants, and Meehan has reason to suspect that the spiders actually wear a sort of insect perfume that makes them smell like their would-be attackers.

More research is forthcoming, including a look at the possibility that spider dad’s help raise the babies, a virtually unheard of behavior in spider biology. In the meantime, I hear Meehan and Olson’s methods included high-definition video of these smarty-pant vegetarian spiders. Now that would be some footage to see.

Meehan and Olson’s study is available in the October 12 issue of Current Biology.


Monarch flycatchers: Catching the moment one bird species becomes two

Plumage variations of the monarch flycatcher. (Photo/Courtesy J. Albert Uy)

Plumage variations of the monarch flycatcher. (Photo/Courtesy J. Albert Uy)

How do you measure the instant one species becomes two? Well, in the Solomon Islands, biologist J. Albert Uy is trying to pick a fight with monarch flycatchers to find the answer. The fight’s tipping point has to do with a bunch of feathers, a change in plumage colors that is allowing scientists to capture a snapshot of evolution in action.

A territorial flycatcher (Monarcha castaneiventris castaneiventris) aggressively responding to a taxidermy mount during our mount presentation experiment. We used mount presentation and song playback experiments to test if divergent plumage color and song are used in species recognition between sister taxa (described in Uy et al. 2009). (Photo/Courtesy J. Albert Uy)

A territorial flycatcher (Monarcha castaneiventris castaneiventris) aggressively responding to a taxidermy mount during our mount presentation experiment. (Photo/Courtesy J. Albert Uy)

Flycatcher males are territorial and will launch an avian smackdown towards perceived rivals trespassing on their turf. But a flip of a single gene is turning the monarch flycatcher into a bird of a different color, and in the process changing the social dynamics of rival birds.

It seems that though they are technically still the same species, the black-feathered flycatcher didn’t get the memo about their chestnut-bellied kin, and vice versa. Uy tested this by invading flycatcher territory with dummy birds. What he’s found is that the two don’t see each other as rivals, and are therefore probably more interested in mating with their like-feathered counterparts.

At least in the case of the monarch flycatcher, this single gene and spot of color heralds the birth of an entire new species.

J. Albert Uy (Photo/ C. Low, courtesy J. Albert Uy)

J. Albert Uy (Photo/ C. Low, courtesy J. Albert Uy)

We often hear about species being lost, but rarely do we learn of one being created. Uy’s work provides a glimpse of the “fork in the evolutionary road” as it happens in real-time, and what that could mean for our understanding of bird life.

Uy’s work appears in the current edition of American Naturalist, and you can read more about monarch flycatchers in the 2005 New York Times article, “In Give and Take of Evolution, a Surprising Contribution from Islands.”


Bait fisheries drive decline of bird species

(Photo/Andrew Easton, 2004)

(Photo/Andrew Easton, 2004)

Every year the horseshoe crabs gather to spawn, releasing thousands of eggs along the Delaware Bay coast. And with timing perfected by evolution, red knots, a bird enduring one of the most impressive yearly migrations from the Arctic to the Tierra del Fuego, arrive just in time to gorge on the eggs of the horseshoe crab. It is a vital stop on the “peeps’” spring migration. But the crabs and their eggs are disappearing, a loss with dire consequences for the little birds.

Red knot populations have fallen more than 75 percent in recent years, and new research published in this month’s issue of Bioscience reveals that Red knots can thank the bait fisheries for their hungry stomachs. Within half a decade the fisheries harvesting horseshoe crabs grew 20-fold, gobbling up more than 2 million crabs a year and effectively eliminating 90 percent of the eggs that red knots rely upon to survive their almost 19,000 mile migration.

But this research is not just a blame game for the fisheries. A coalition of scientists worked together on this study to help draft recommendations for the adaptive management of the bait fisheries that could help all three groups survive.


An upside to climate change?

They’re the five “dirty words” of the West — cheatgrass; spotted knapweed; yellow starthistle; tamarisk; and leafy spurge — but the battle against these pervasive troublemakers could receive a boost from an unlikely ally, climate change. Scientists from Princeton University have determined that climate change will very likely cause massive die-offs of these invasive plants across the West, creating unprecedented opportunities to restore millions of acres of infected wilderness to native vegetation.

The findings, released this month in the journal Global Change Biology, will help land managers develop long-term invasive plant recovery projects. The restorative potential comes at a price however, as the model used in the study also predicts that some populations of invasive plants may simply shift their ranges to new areas — yellow starthistle will likely move from its current range in California, Oregon and Washington to a new ranges in California and Nevada for example.

Either way, the study forecasts a new picture of the western landscape, and may help researchers treat or possibly prevent invasive plant infestations. Whether the prognosis is good or bad, this is potentially important news for land managers and residents.


Snoozing through Climate Change

Hitting the snooze button might be a good idea for mammals trying to cope with global warming. Research published this month in The American Naturalist, reveals mammals that hibernate or burrow have a better chance of surviving extinction because of climate change.

Dr. Lee Hsiang Liow of the University of Oslo and his colleagues studied fossil records and found that “sleep-or-hide” mammals lasted longer than other animals as a species. Liow then compared current species trends with animals listed on the International Union for the Conservation of Nature Red list — one detailing the risk status of the world’s biodiversity. What Liow found was that, just like in the fossil record, modern mammals that hibernate or burrow tend to weather climate change better than non-burrowers.

The benefit comes at a price, however, while the critters might be better at coping with climate change, they could be slow to evolve themselves. This leaves “sleep-or-hide” mammals in the proverbial dust as other animals adapt more quickly.

“Sleep-or-hide species survive longer, but in a changing world they run the risk of eventually becoming seriously obsolete,” said Mikael Fortelius of the University of Helsinki, in a press release, “in a way it’s the classic choice between security and progress.”


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