02252nas a2200229 4500008004100000022001400041245010200055210006900157260001200226490000800238520151000246653002601756653002401782653001501806653001701821653001901838100001801857700002101875700002701896700002501923856007401948 2014 eng d a0962-845200aMutualism between co-introduced species facilitates invasion and alters plant community structure0 aMutualism between cointroduced species facilitates invasion and  c12/20140 v2823 a

Generalized mutualisms are often predicted to be resilient to changes in partner identity. Variation in mutualism-related traits between native and invasive species however, can exacerbate the spread of invasive species (‘invasional meltdown’) if invasive partners strongly interact. Here we show how invasion by a seed-dispersing ant (Myrmica rubra) promotes recruitment of a co-introduced invasive over native ant-dispersed (myrmecochorous) plants. We created experimental communities of invasive (M. rubra) or native ants (Aphaenogaster rudis) and invasive and native plants and measured seed dispersal and plant recruitment. In our mesocosms, and in laboratory and field trials, M. rubra acted as a superior seed disperser relative to the native ant. By contrast, previous studies have found that invasive ants are often poor seed dispersers compared with native ants. Despite belonging to the same behavioural guild, seed-dispersing ants were not functionally redundant. Instead, native and invasive ants had strongly divergent effects on plant communities: the invasive plant dominated in the presence of the invasive ant and the native plants dominated in the presence of the native ant. Community changes were not due to preferences for coevolved partners: variation in functional traits of linked partners drove differences. Here, we show that strongly interacting introduced mutualists can be major drivers of ecological change.

10aco-introduced species10ainvasional meltdown10amutualisms10amyrmecochory10aseed dispersal1 aPrior, K., M.1 aRobinson, J., M.1 aDunphy, S., A. Meadley1 aFrederickson, M., E. uhttp://rspb.royalsocietypublishing.org/cgi/doi/10.1098/rspb.2014.2846