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

In the mediterranean ecosystems of South Africa and Australia, the rol e of ants in the dispersal of seeds is well known and antagonistic int eractions as well as myrmecochory occur. The high prevalence of seed d ispersal by ants, relative to that by vertebrates, is viewed as eviden ce of adaptation to the nutrient poor soils typical of these environme nts. Ant dispersal has been considered unimportant in the Mediterranea n region and, until now, no systematic study of ant-seed interaction h as been undertaken. In the Mediterranean shrubland of Southern Italy t he seed content of functioning nests of the ant Messor minor (Andre) h as been quantitatively analyzed. The existence in the nest of seeds fr om shrub species, as well as those of the Fabaceae and Poaceae, sugges t that ant dispersal may be much more widespread in the Mediterranean environments than has been realized. A large proportion of the seeds c ame from fleshy-fruited shrub species previously reported to be bird d ispersed, 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 b y the ants, a very large number had been collected, transported to the nest and subsequently removed to the mound without damage. Examinatio n of the structure of the fruits and seeds of Ii. alaternus and M. com munis, 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.