SEED DISPERSAL CURVE OF A MEDITERRANEAN MYRMECOCHORE - INFLUENCE OF ANT SIZE AND THE DISTANCE TO NESTS

Euphorbia characias is a Mediterranean spurge with a diplochorous disp ersal system: after a ballistic dispersal that scatters the seeds, som e ant species find and retrieve the seeds to their nest (myrmecochorou s dispersal). The seed dispersal curve generated by ants in an abandon ed field was described and partitioned according to ant size and to th e distance to nest entrance from where seeds fell after ballistic disp ersal. Both variables (ant size, distance to nest) affected dispersal distance. The seed dispersal curve showed a peak at short distance (me dian = 1 m) and a tail extending to 9.4 m. The peak and the tail are e xplained differently. Short distances are usually generated by small a nts (Pheidole pallidula and Tapinoma nigerrimum; 0.56 +/- 0.41 m [n = 48]) both from the nearest or farther nest entrances. The tail of the curve is generated disproportionately by big ants (Aphaenogaster senil is and Messor barbarus, 2.09 +/- 1.71 m [n = 61]) from farther nests. Seeds have a much greater probability (P = 0.734) of being transported to nests which are not the nearest. This effect is largely due to tra nsportation by big ants.