SPATIAL VARIATION IN THE INTERACTIONS BETWEEN PRUNUS MAHALEB AND FRUGIVOROUS BIRDS

In three nearby habitats which differ in both vegetation structure and floristic composition, and presumably also in bird species composition, Prunus mahaleb fruits are eaten by different bird species. As a consequence of this variation and of the bird species differing in both their fruit handling methods and seed-dispersing efficiency, there is among-habitat variation in the proportion of fruits that are swallowed whole in situ, carried away, pecked, destroyed to eat the seeds and dropped to the ground. To the extent that the seed dispersal success affects plant fitness, this variation may result in spatial variation in the selective pressures acting upon the plant. However, the spatial scale on which these changes occur is probably too small for the differentiating effect of natural selection, in case it is acting, to override the homogenizing effect of gene flow.