I could do without the patronizing narration, but National Geographic’s footage of Pseudomyrmex acacia-ants is worth your time:
Argentine Ants have spent the past century following commerce around the world, aggressively subsuming the territories of native ants. However, a study by Meghan Cooling et al out today in Biology Letters reports a dent in the Argentine ant empire:
Argentine ants had disappeared from 40 per cent of our sampling sites. In many other sites, Argentine ant populations had been reduced from occupying multiple nests encompassing large areas to one or two small nests in a few square metres. These results are consistent with our observations of the slow shrinkage and disappearance of large Argentine ant infestations in areas, such as Wellington. They do not appear to move and to our knowledge are not managed by humans in any way that might reduce their abundance.
This result echos anecdotes I’ve heard from several people in California. Places once thick with Argentine ants have returned, in part, to a native fauna.
Cooling et al pair their collapse data with climate models to predict whether the process will continue under global warming. I wish they hadn’t. Without knowing the cause of the collapse (pathogens?) the whole climate model exercise is silly. Can’t a straightforward ecological finding just be published on its own?
Source: Cooling, M. et al 2011. The widespread collapse of an invasive species: Argentine ants (Linepithema humile) in New Zealand. Biology Letters, Published online before print , doi:10.1098/rsbl.2011.1014
Pest insects can be unpredictable, arriving in unexpected places yet failing to show up in regions where they ought to thrive. The famously defensive Africanized honey bees, for example, took more than a decade to move into Florida after establishing in nearby Texas.
Argentine ants (Linepithema humile) are a subtropical species from flood plains in the warmer, wetter regions of Argentina. Yet a persistent mystery about their world conquest has been their success in dry Mediterranean climates and in more northerly locations than predicted by their South American range. Now, though, a paper by Brightwell & Silverman in Environmental Entomology has answered the northern mystery, at least in part: native pine trees give the ants a winter refuge.
Figure one from the study shows pine trees maintaining high levels of ants during the winter while other trees lose them:
Apparently, those tall trunks are ideal for capturing winter sunlight. The bark stays warmer than ambient temperatures, creating a livable micro-climate, and ants continue foraging along the trunks throughout the winter.
These sorts of microhabitat effects are hugely important, especially for small organisms like ants. For those attempting to make future range predictions from crude climate data (as though I would ever do that!), these quirks of the real world are worth bearing in mind.
*update* smart comments over at G+.
source: Brightwell, R.J., Silverman, J. 2011. The Argentine Ant Persists Through Unfavorable Winters Via a Mutualism Facilitated by a Native Tree. Environmental Entomology, 40(5):1019-1026. 2011.
Rachelle Adams, who studies Megalomyrmex ants, sends word of a new tropical eco/evo class in Panama for graduate students:
The Smithsonian’s Tropical Research Institute in Panama has been ground zero in tropical biology for decades, and this course looks to put you right in the middle of it. The application deadline is March 1st.
This shot may look like it came from an exotic location, but in fact I snapped it not three hours ago in our prairie garden. The sideoats grama is flowering, and its tiny blossoms are positively buzzing with miniature halictid bees, each barely half a centimenter long.
Canon EOS 7D camera with a Canon 100mm f2.8 macro lens
ISO 500, f5.6, 1/200 sec
diffuse overhead flash, handheld
If I had to pick the most annoying insect in Illinois it’d be Harmonia axyridis. This lady beetle was introduced to our continent as a control agent for aphids but became a pest in its own right. It consumes not just aphids but all manner of other insects, including beneficials like native lady beetles. Swarms of them descend into our houses in the fall. They get just about everywhere. They have a noxious odor. And they bite.
A study out in PLoS One byLombaert et al has determined that our local beetles here in eastern North America are the culprit behind a spate of recent invasions elsewhere in the world. The researchers extracted DNA from 18 loci across the various populations, modeled several different introduction scenarios, and concluded that one story makes the observed genetic data the most likely. It’s this one:
The authors call this result “surprising”, but I disagree. If a pest builds to enormous numbers in a region that sees a lot of commerce, exports of that pest may become much more likely than exports from the native range. Especially if native populations are kept down by predators and competition.
We see this in ants all the time. The invasive Argentine ants in California arrived from an earlier invasion to the eastern U.S., not as a separate colonization from Argentina. Fire ants in Australia appear to be from the United States, not South America.
In any case, it’s an interesting and timely study. Now, if they could just figure out where I can send the beetles in my house so they don’t come back, that’d be really valuable.
source: Lombaert E, Guillemaud T, Cornuet J-M, Malausa T, Facon B, et al. 2010 Bridgehead Effect in the Worldwide Invasion of the Biocontrol Harlequin Ladybird. PLoS ONE 5(3): e9743. doi:10.1371/journal.pone.0009743
I did not expect everyone to nearly instantaneously solve yesterday’s termite ball mystery. I’m either going to have to post more difficult challenges (from now on, nothing will be in focus!) or attract a slower class of reader.
As you surmised, those little orange balls are an egg-mimicking fungus. It is related to free-living soil fungi, but this one has adopted a novel growth form that is similar in diameter, texture, and surface chemistry to the eggs of Reticulitermes termites. These hardened sclerotia are carried about the termite nest as if they were the termite’s own offspring, earning them the title “Cuckoo fungus”. Since termites are blind there is no advantage to the fungus in visually looking like an egg, though, so we sighted creatures can tell the difference at a glance.
For more about the Cuckoo fungus, check out the publications of Kenji Matsuura. Matsuura first identified the balls as a fungus ten years ago, as a graduate student, and has been working on them ever since.
Surfing around the bookstores this morning I see that the much-anticipated Ant Ecology book is out. At $129.00 it’s not something the casual reader is liable to pick up. Nonetheless, Ant Ecology is a beautiful volume reviewing the state of the field, and scientists who work on ants should probably own a copy. Or at least get one on time-share.
The book is a collection of 16 chapters edited by Lori Lach, Kate Parr, and Kirsti Abbott. There’s a mellifluous forward by Ed Wilson, but then, most ant books have a mellifluous forward by Ed Wilson. Ant Ecology‘s real strength is that each chapter is written by researchers actively working on their chosen topics. Thus, the full volume is a collaboration across the leading edge of myrmecology, and the perspectives they offer are a glimpse into the burning scientific questions of the day from the mouths of the very people working hard at answering them. Among others, Brian Fisher covers ant biogeography, Christian Peeters does ant life history, and Anna Dornhaus & Scott Powell write about ant foraging strategies. As a teaser, Amazon previews part of Phil Ward’s chapter on systematics here.
I’m still only a couple chapters in, so that’s all the detail you get for now.
disclaimer: You probably shouldn’t trust me for an unbiased review. I provided most of the book’s images, and many of the authors are friends of mine. Plus the editors- bless them- sent along some simply lovely ant attire as thanks for the images (I’ll post photos shortly…)
If I were to mention an ant-fungus mutualism- that is, an ecological partnership between an ant and a fungus that benefits both- most biologically literate people might think of the famed leafcutter ants and the edible mycelia they cultivate. But that is just one example.
Several other fungi have entered into productive relationships with ants, assisting especially in ant architecture. Consider:
An ant lion captures prey not by passively sitting at the bottom of its sand trap, but by aggressively flinging debris at its target, enveloping it in a sand storm.Continue reading →