Seed production, predation and dispersal in the Mediterranean myrmecochore Euphorbia characias (Euphorbiaceae)

Seed production of a population of 193 reproductive individuals of Euphorbia characias from the north-east Iberian peninsula was estimated at 155 000 seeds per year. The dehiscence period lasts for four weeks. The timing of ballistic dispersal is uniformly distributed throughout the day. Seeds remain on the surface a mean time (± SE) of 52.3 ± 6.7 min. Several ant species take the seeds in varying proportions: Messor barbarus (0.225), a granivorous ant which eats the seeds; Aphaenogaster senilis (0.313), Pheidole pallidula (0.296) and Tapinoma nigerrimum (0.162) which take the seeds to their nests but do not eat them. Half a million ant foraging trips per day indicate a very strong short term influence of ants on fate of Euphorbia seeds. Ants as a group have a dual role of predation and dispersal of Euphorbia characias seeds. The characteristics of this Euphorbia (sclerophylly, diplochory, firmness of elaiosome, absence of subsidiary myrmecochorous features) better fit the syndrome described for Australian myrmecochores than the one proposed for European and North American myrmecochores.