FIRST EVIDENCE OF MYRMECOCHORY IN FLESHY-FRUITED SHRUBS OF THE MEDITERRANEAN REGION

In the mediterranean ecosystems of South Africa and Australia, the role of ants in the dispersal of seeds is well known and antagonistic interactions as well as myrmecochory occur. The high prevalence of seed dispersal by ants, relative to that by vertebrates, is viewed as evidence of adaptation to the nutrient poor soils typical of these environments. Ant dispersal has been considered unimportant in the Mediterranean region and, until now, no systematic study of ant-seed interaction has been undertaken. In the Mediterranean shrubland of Southern Italy the seed content of functioning nests of the ant Messor minor (Andre) has been quantitatively analyzed. The existence in the nest of seeds from shrub species, as well as those of the Fabaceae and Poaceae, suggest that ant dispersal may be much more widespread in the Mediterranean environments than has been realized. A large proportion of the seeds came from fleshy-fruited shrub species previously reported to be bird dispersed, e.g. Rhamnus alaternus L., Myrtus communis L., Smilax aspera L., Pistacia lentiscus L. and Phillyrea latifolia L. Analysis of nest mounds showed that, although many seeds had been partially predated by the ants, a very large number had been collected, transported to the nest and subsequently removed to the mound without damage. Examination of the structure of the fruits and seeds of Ii. alaternus and M. communis, and summer fruiting phenology of R. alaternus, provided further evidence of specific adaptation to ant dispersal. The presence of an elaiosome on the seed is reported for the first time in both species. Feeding trials showed that ants selectively remove specific diaspores, preferentially collecting the seeds with the elaiosome.