Media Releases

European fire ant impacts forest ecosystems by helping alien plants spread

December 24, 2014

TORONTO, ON — An inva­sive ant species that has become increas­ing­ly abun­dant in east­ern North Amer­i­ca not only takes over yards and deliv­ers a nasty sting, it’s help­ing the spread of an inva­sive plant species.  The ants are very effec­tive dis­persers of inva­sive plant seeds and new research sug­gests that togeth­er they could wreak hav­oc on native ecosys­tems.

Uni­ver­si­ty of Toron­to researchers have found that the Euro­pean fire ant, Myr­mi­ca rubra, dis­pers­es seeds of both native and inva­sive plants, but it does a much bet­ter job of help­ing an inva­sive plant to spread.

“Ecol­o­gists think inva­sive species might help each oth­er to spread, but there are few good exam­ples. They talk about ‘inva­sion­al melt­down,’ because ecosys­tems could be very, very rapid­ly tak­en over by inva­sive species if invaders help each oth­er out,” said evo­lu­tion­ary biol­o­gist Megan Fred­er­ick­son, one of the authors of the study, pub­lished in the jour­nal Pro­ceed­ings of the Roy­al Soci­ety B. “Our results sug­gest that inva­sion­al melt­down could be hap­pen­ing right under our noses, here in Ontario.”

The research was con­duct­ed at U of T’s field sta­tion, the Kof­fler Sci­en­tif­ic Reserve at Jok­ers Hill ( The team cre­at­ed arti­fi­cial eco­log­i­cal com­mu­ni­ties – meso­cosms – inside 42 small plas­tic children’s swim­ming pools.

The researchers filled each pool with soil and plant­ed four species of spring wild­flow­ers  –three native species (sharp-lobed hepat­i­ca, Cana­di­an wild gin­ger and blood­root) and one inva­sive species: greater celandine. They then col­lect­ed colonies of either the Euro­pean fire ant or a native wood­land ant and added the colonies to the pools. The ants picked up and moved seeds of these plant species and the researchers watched what hap­pened.

“The pools with the inva­sive ant were over­run by the inva­sive plant, but pools with the native ant had lots of native plants,” says co-author and ecol­o­gist Kirsten Pri­or. The inva­sive ant moved lots of seeds of all four plant species, but the inva­sive plant took advan­tage of being dis­persed more than the oth­er species and recruit­ed in very large num­bers.

“Unfor­tu­nate­ly, as a result of humans rapid­ly mov­ing species around the globe through trade and traf­fic, most ecosys­tems are now home to numer­ous inva­sive species,” said Pri­or. “Our find­ing that mul­ti­ple inva­sive species can accel­er­ate inva­sion and cause ecosys­tems to become dom­i­nat­ed by inva­sive species is a trou­bling one. Inva­sive species are a lead­ing threat to nat­ur­al ecosys­tems, and can have impacts on soci­ety. Research on how ecosys­tems become invad­ed and the con­se­quences of inva­sion is impor­tant. It sets us on the right path to devel­op solu­tions to reduce the spread and impact of these harm­ful species.”

Oth­er research team mem­bers includ­ed under­grad­u­ate stu­dents Jen­nifer Robin­son and Shan­non Meadley Dun­phy.  Research was fund­ed by the Nat­ur­al Sci­ences and Engi­neer­ing Research Coun­cil and the Ontario Min­istry of Eco­nom­ic Devel­op­ment and Inno­va­tion.

Images and paper at

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Kirsten Pri­or
Depart­ment of Biol­o­gy
Uni­ver­si­ty of Flori­da
Cell/Mobile: + 254–202- 639–251 *  Kirsten is in Kenya . Note that Kenya is 8 hours ahead of Toron­to time.

Megan Fred­er­ick­son
Depart­ment of Ecol­o­gy & Evo­lu­tion­ary Biol­o­gy
Uni­ver­si­ty of Toron­to
Cell/Mobile: +1 647–224-4449

Kim Luke
Com­mu­ni­ca­tions, Fac­ul­ty of Arts & Sci­ence
Uni­ver­si­ty of Toron­to
Tel: 416–978-4352