Tag Archive for introduced ants

Pheidole flavens-complex introduced to the southwestern Pacific

Here’s the story behind the new Bioinvasions Records article on that just came out. Christian Rabeling and Ed Wilson went to Vanuatu a few years back in 2011 because it was one of the few Melanesian islands that Wilson had never collected from. They collected all the ants they could find in a general survey and kindly sent their Pheidole to the Economo lab at OIST so that I could match them against our other Pacific Pheidole collections and Evan could include them in our phylogenetic analysis. Christian and Ev caught some great Pheidole from the island, including this beautifully spinescent endemic from the sexspinosa complex shown below (CASENT0282641).

An elegant Vanuatu endemic ant species (Pheidole epem198, CASENT0282641) from the Pheidole sexspinosa complex

But one species came out in an unexpected branch on the phylogeny. Instead of coming out with the Old World clade with all the other native Melanesian ants, this one species was reliably nested within the New World clade. It’s closest relatives on the tree were two species that had been included in Corrie Moreau’s 2008 Pheidole phylogeny and id’d as P. moerens and P. flavens–both of which are considered to be invasive.

Major worker of a species from the Pheidole flavens-complex from Espiritu Santo, Vanuatu; collection code CR111110-15, specimen code CASENT0248836. (1) Lateral view, (2) fullface view, (3) dorsal view, (4) hypostomal bridge.

Major worker of a species from the Pheidole flavens-complex from Espiritu Santo, Vanuatu; collection code CR111110-15, specimen code CASENT0248836. (1) Lateral view, (2) fullface view, (3) dorsal view, (4) hypostomal bridge.


Minor worker of a species from the Pheidole flavens-complex from Espiritu Santo, Vanuatu; collection code CR111110-15, specimen code CASENT0248835. (5) Lateral view, (6) fullface view, (7) dorsal view

We wanted to let other researchers know about the spread of this trampy species into the Pacific, so we wrote up a rapid communication article for Bioinvasions Records. The idea was to get the basic information about the new discovery out as quickly as possible, so others in the region could be on the lookout for additional incursions.

The most frustrating part of this study was trying to get a name on the species. Unfortunately, the taxonomy of P. flavens and its close relatives like P. moerens and P. exigua is a super sticky mess, rife with infra-specific names, lost holotypes, and inaccurate determinations. It seems like these taxonomic morasses plague trampy species (like P. flavens and friends) much more often than your average ant species.

Why is it that trampy species so often belong to species-complexes? What are species-complexes, anyways? I suppose I’d define them as geographically distinct populations that are somewhere on the continuum of streching from a recently coalesced species radiation on one end to a network of geographically isolated groups with some low amount of gene flow still persisting. For the taxonomist or even the molecular systematist there is no clear way to know whether to call these things five geographically isolated species or one widespread species.

Whatever the population on Vanuatu turns out to be, it doesn’t match the neotype of P. flavens or the syntypes of P. moerens, so for now we have to settle for calling it a member of the flavens-complex and hope that someone tries to untangle this taxonomic knot in the near future.

EM Sarnat, C Rabeling, EP Economo & EO Wilson (2014) First record of a species from the New World Pheidole flavens-complex (Hymenoptera: Formicidae) introduced to the southwestern Pacific. Bioinvasions Records 3: 301-307. | PDF


How to identify Solenopsis invicta using Antkey

In this tutorial I demonstrate a few different approaches to identifying Solenopsis invicta, also known as the Red Imported Fire Ant (RIFA), using Antkey. The key can be accessed at antkey.org/content/key.

How to identify Solenopsis invicta using Antkey from Eli Sarnat on Vimeo.

How to use Antkey’s Lucid3 interactive key

In this tutorial I demonstrate how to make the most effective use of Antkey’s interactive Lucid3 key for identifying invasive and introduced ants. There are tips on how to use features like the ‘best’ and ‘next best’ buttons, what the different panels mean, how to make effective use of thumbnail and pop-up images and how to adjust the text size.

How to use Lucid Key for identifying ants from Eli Sarnat on Vimeo.

Antkey release

Andy Suarez and I are excited to announce the release our Antkey.org project. The project was funded by USDA-APHIS-PPQ-CPHST and the Encyclopedia of Life (EOL) Rubenstein Fellowship program to provide an online identification guide to invasive, introduced and commonly intercepted ants.

Download USDA Antkey Announcement

Frontpage of the Antkey.org site


Over 15,000 species of ants have been described, and more than 200 have established populations outside of their native ranges. A small subset of these have become highly destructive invaders including five which are currently listed among the world’s 100 worst invasive species. Unfortunately, detection of non-native ants is hampered by the taxonomic specialization required for accurate species identification.  Antkey seeks to mitigate the spread of established introduced ants and prevent the incursion of new introductions by providing quarantine personnel, inspectors and conservation biologists with a user-friendly identification resource specifically designed for non-specialists.

Antkey focuses on over 115 ant species that are introduced, invasive or commonly intercepted in North America and the Pacific Islands. Features include an interactive Lucid key, dynamically generated species pages, a searchable media collection of over 1150 images, over 70 live video clips of introduced ants, a fully illustrated glossary with over 400 terms, a searchable database of introduced ant literature, over 12,000 specimen records of introduced ants imported from Antweb (www.antweb.org), and community features such as blogs, discussion forums and comment options.

Tabbed species page for Linepithema humile on Antkey.org

The interactive Lucid key allows users to start at multiple entry points, skip ambiguous or difficult characters, and keep track of the choices already made. Novice users can use the ‘best’ feature to determine which available characters will lead to the most parsimonious pathway. More advanced users can skip straight to subfamily or genus. The characters are illustrated with original line drawings and link to glossary definitions and additional specimen photographs.

The Antkey taxonomic classification includes 8 subfamilies, 43 genera and 116 valid species. Taxon pages include tabs for overview, descriptions, media, maps, literature and specimens. In addition to original diagnostic descriptions and overview sections, all the species pages dynamically import relevant articles from the Encyclopedia of Life (www.eol.org) and specimen images from Antweb. The Google maps are dynamically generated from specimen data imported from Antweb and distribution data imported from GBIF.

The media feature contains over 1150 images and uses a faceted search tool that allows users to filter images by media gallery, taxonomic name, keywords, description and creator. Each thumbnail links to a lightbox window that displays the standard scaled image and associated metadata, and also offers a link to download the original, full-sized image. All images tagged with a taxon name automatically appear on that taxon’s species page.

Media feature in Antkey allows users to filter their searches based on morphological terms, taxonomic names, image type, media galleries and keywords.

The site includes approximately 75 video clips of 22 species. There are many important identification characters for ant species that are only possible to detect while the ant is alive. The standardized thirty-second video clips feature ants feeding at and recruiting to baits, foraging in natural environments, and entering and exiting their nests. The videos can be downloaded by users or embedded in other webpages.

A fully illustrated glossary of over 400 terms, including all the character states used in the Lucid key, allows users to quickly learn the important morphology needed to make accurate identifications. The terms are integrated throughout the site so that whenever one appears in the text the user can point to it and the definition will automatically display.

One of the greatest strengths of Antkey is that it was developed using the Scratchpads platform.  Scratchpads (http://scratchpads.eu/) is a social networking platform that allows communities to bring taxonomic information together without the limitations of traditional paper-based publications. Web systems and content can be developed and updated in minutes so websites can reflect the latest knowledge of a particular group. The platform also allows multiple authors to create and edit content without using any html code. The Scratchpads platform relies on the content management system Drupal (http://drupal.org/) for its underlying architecture.

Introduced Nylanderia of the United States

I’ve spent the last couple of days parsing the differences among the many introduced species of Nylanderia. I still haven’t gotten a good look at the Rasperry Crazy Ant or Caribbean Crazy Ant or the Hairy Crazy Ant or whatever folks are calling the species that has been spreading across the southeastern United States, but apparently it is close to N. fulva and N. pubens. Hopefully John LaPolla’s revision of the Nearctic Nylanderia will be out soon, and I’ll be able to update my provincial key characters.

In the meantime, here’s a link to an illustrated comparison chart of Nylanderia introduced to the United States (including Hawaii).

And here’s a gallery of the various illustrations I’ve put together thus far for the key.

Selected references and resources of introduced Nylanderia species. (Note that all these species of Nylanderia were treated as Paratrechina prior to LaPolla et al. (2010)).

Trager, J.C. (1984) A revision of the genus Paratrechina (Hymenoptera: Formicidae) of the continental United States. Sociobiology, 9, 49-162. [Includes keys and descriptions of N. bourbonica, N. flavipes, N. guatemalensis, N. fulva, N. vividula all in addition to the native species].

LaPolla, J. S.; Hawkes, P. G.; Fisher, B. L. 2011. Monograph of Nylanderia (Hymenoptera: Formicidae) of the World, Part I: Nylanderia in the Afrotropics. Zootaxa 3110:10-36. [PDF] [Covers three spp. of Nylanderia purportedly introduced to the Afrotropics, including N. bourbonica, N. vaga and N. vividula.]

LaPolla, J.S., Brady, S.G. & Shattuck, S.O. (2010) Phylogeny and taxonomy of the Prenolepis genus-group of ants (Hymenoptera: Formicidae). Syst. Entomol., 35, 118-131. [PDF]

Ivanov, K. & Milligan, J. (2006) Paratrechina flavipes (Smith) (Hymenoptera: Formicidae), a new exotic ant for Ohio. Proc. Entomol. Soc. Washington, 110, 439-444. [Nice small paper on N. flavipes and how to distinguish it from N. vividula.]

Ants of the Southeastern United States – key to species of Nylanderia. [Excellent website of Joe MacGown with a key adapted from Trager (1984).]

Vollenhovia emeryi in Washington DC

Vollenhovia emeryi nesting in dead log. Notice how these cylindrical short-limbed ants are so adept at weaving among their shallow nest tunnels. This colony had hundreds of workers and many queens. Units in mm. Collection data: USA Washington DC, C&O Canal, 16.vi.2011, 38.902739°, 77.057704°, 3m, E.M. Sarnat.

Vollenhovia emeryi is one of the more recent ants to have established in North America. The first record of this Japanese transplant came from Stefan Cover of Harvard’s Museum of Comparative Zoology. Cover discovered the species in 1986 while sampling for ants in Washington, DC. Vollenhovia species tend to be generalists and the native range of the genus is restricted to Asia, northeastern Australia, and the Pacific Islands, and are not generally thought of as successful tramp ants.

How then did this demure little species come to arrive in the capital city of the United States? The answer might be linked to a tale often told of that city’s namesake, George Washington. Legend has it that when George Washington was a six-year-old lad he chopped down a cherry tree. When confronted by his father, young George replied, “I cannot tell a lie, father, you know I cannot tell a lie! I did cut it with my little hatchet.”

Cherry trees may, in fact, have been how Vollenhovia emeryi became introduced into the United States. Japan has gifted the cities of Washington DC and Philadelphia thousands of cherry trees during the past century, many of which were planted in localities where V. emeryi is known to occur. Dan Kjar raises the possibility that colonies of these little ants stowed away in the rootballs of the cherry trees, and have slowly been expanding their range along the riparian habitats of the District of Colombia, Virginia, Maryland, and Pennsylvania ever since.

During my recent research trip to the Smithsonian’s entomology collection I took a brief expedition in search of a Vollenhovia emeryi colony to collect and film. Dan Kjar suggested I take a look around the C & O Canal area near Georgetown. By the time I exited the Metro station it was pouring down rain, so I concentrated my search to a relatively dry area under a freeway overpass. Searching for invasive ants often leads one to rather unsavory habitats, such as dumps, ports, and urban filth. After turning over all variety of garbage and refuse in search of a colony, I finally found one nesting under a dry branch.

Eli Sarnat collecting live colony of Vollenhovia emeryi from beneath an overpass in Washington DC. Notice the graffiti and garbage strewn across the site. Invasive ant research is not always the stuff of romance.

I took some video of the ants as they scurried about in their signature slinky style. Then I searched about the garbage some more until I found a suitable empty Gatorade bottle and a mismatched cap into which I collected the live colony. The colony had many queens, so I split it in two. One colony is now residing happily in Ted Schultz’s ant lab at the Smithsonian, and the other is at the Suarez Lab at UIUC. Alex Wild took some excellent photographs of these ants from the Suarez lab colony that are available on his Myrmecos website.