Posts Tagged ‘invasive species’

Harmonia axyridis, the Asian Multicolored Lady Beetle

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:

Figure 1 from Lombaert et al 2010 showing the most likely path of introductions of H. axyridis.

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

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Anochetus mayri

Anochetus mayri is an ant most North American myrmecologists will not have encountered in the field.  This toothy exotic is a small brown insect, less than half a centimeter long, known in the United States only from scattered locations in suburban Florida.  I photographed one this summer on a collecting trip to West Palm Beach.

Anochetus mayri illustrates a couple recurring themes in myrmecology.  (more…)

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Survivor: Invasive Ants

from an interview with Survivor contestant Kelly Sharbaugh:

When your name showed up, you looked flabbergasted, shocked, dumbfounded.
All of the above. I had no idea that Russell had the idol. When [host Jeff Probst] said my name, I was like. “What just happened? What did I do?” I was so emotional because I was so unprepared. I didn’t even wear my favorite boots to tribal because the thought that I could go never crossed my mind.

Did you ever get them back?
No, fire ants nested in them so I left them in Samoa and after the tsunami I’m pretty sure they got washed away.

Good for Kelly, I say, for helping stop the spread of pest ants.  When contestants are voted off the island, how many do you suppose check their luggage for invasive species?


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The ant invasions continue…

In the past week:

Solenopsis invicta reaches Missouri

Wasmannia auropunctata reported on Maui


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From my inbox, a postdoctoral job announcement:

The Department of Botany, La Trobe University, Melbourne, Australia seeks to appoint a Postdoctoral Fellow to conduct research in Invasion Biology on Christmas Island.  Over the last decade, supercolonies of the invasive yellow crazy ant Anoplolepis gracilipes have spread across island rainforest and caused a variety of significant impacts.  High ant densities are consistently associated with high densities of exotic honeydew-secreting scale insects. This project will determine the dependence of ant supercolonies on associated scale insects specifically, and the role of mutualism in facilitating biological invasions generally.  We are looking for a well motivated, independent person with a track record of research in multi-species interactions. Experience with large-scale field experiments and stable isotope analysis would be an advantage. The three-year position will be based on the island, which is an external territory of Australia.

To view the full application, click here.  The deadline is March 27.  Contact Dr Dennis O’Dowd (odowd [at] sci.monash.edu.au) or Dr Peter Green (p.green [at] latrobe.edu.au) for more information.

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The port at Mobile, Alabama, photographed from across the bay.

The port city of Mobile, Alabama holds special significance for students of ant science.  Jo-anne and I took a weekend trip down to the gulf coast in January, and as we are both myrmecologists we felt compelled to stop and take a few photographs.  Not only is Mobile the childhood home of ant guru E. O. Wilson, but the city’s docks have been the point of introduction into North America for some notorious pest ants.  We’d have neglected our intellectual heritage to just drive through.


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humilewhite There’s been a debate simmering among Argentine Ant researchers about the difference between the ant’s ecology in its native South America and in the introduced populations.  The heart of the disagreement is this:  is the introduced Argentine ant dominant because its biology changed during introduction, or because the ecologies of the native and introduced ranges are different?

Like most scientific debates, some aspects are factual in nature while others are semantic.  Sometimes the semantic and the factual become confused in a way that makes it difficult to tease the arguments apart without careful parsing of words, and I think this debate is one of those cases with much needless confusion.

The classic story, raised by Neil Tsutsui et al, is that Argentine Ants passed through a genetic bottleneck at introduction (a natural consequence of founding a new population from a few transported individuals) and the resulting homogenous population lacked the genetic diversity needed to recognize nestmates from non-nestmates.  (more…)

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Pheidole moerens, Louisiana

Pheidole moerens, major worker, Louisiana

Pheidole moerens is a small, barely noticeable insect that travels about with human commerce, arriving without announcement and slipping quietly into the leaf litter and potted plants about town.   As introduced ants go, P. moerens is timid and innocuous- it’s certainly no fire ant.  The species is now present in the southeastern United States, a few places along the west coast, and Hawaii.  Conventional wisdom suggests that P. moerens originated in the Greater Antilles, but even though the ant was first described from Puerto Rico a century ago its exact origin remains uncertain.

The Greater Antilles were a major hub in the global trade of the colonial era, receiving slaves from Africa and shipping sugar north to the distilleries.  A great number of pests had already been carried to the islands by the time European scientists started to fully describe the fauna, so it’s not unlikely that many animals considered native there may have merely used the archipelago as a way-station between their actual origin and their ultimate global distribution.

Now that scientists are equiped with the tools of molecular genetics, we have the ability to determine more precisely the historical routes of spread. It would not take too much work to pin down the origin of P. moerens.  But this ant is just one species of many that are both globally trampy and not particularly troublesome.  Elucidating its origin is thus more an academic than an applied matter, so Pheidole moerens will likely remain mysterious for some time yet.


Pheidole moerens, minor worker, Louisiana

photo details: Canon MP-E 65mm 1-5x macro lens on a Canon EOS 20D
ISO 100, 1/250 sec, f/13, flash diffused through tracing paper

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Pacific Invasive Ants

This just in:  Eli Sarnat’s “Pacific Invasive Ants” website is up.  It’s got something for everyone: fact sheets, videos, keys, links.   Eli’s got an eye for design, too, so the site is aesthetically pleasing and easy to navigate.


(postscript:  yeah, yeah.  Pacific Disturbance Specialist Ants.  I know.)

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Solenopsis invicta- invasive or just disturbed?

Solenopsis invicta - invasive or just disturbed?

Prevailing wisdom holds that imported fire ants marched across the southern United States on the virtue of their fierce nature and superior competitive ability.  The fire ant conquest of the south reads like a tale of bravery and intrigue, but according to Walt Tschinkel and Josh King it is also not true.   They have a must-read study in PNAS this week detailing a tight set of field experiments that turns the conventional wisdom upside-down.


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