How specialized are fruit-bird interactions? Overlap of frugivore assemblages within and between plant species

Both location and plant species identity significantly influence the composition of frugivore assemblages of local plant populations. This is revealed by an analysis of assemblages of pulp-eating birds of European plants. When comparing assemblages of plant populations at different sites, those from the same plant species are more similar to each other than those from different species. Thus, interspecific differences in fruit or plant traits seem to cause recurrent differences in frugivore assemblages. On the other hand, the similarity between the frugivore assemblages of plant populations belonging to different species is significantly higher if the populations grow at the same site. This site effect seems to be as strong as the species effect. The similarity within sites is not statistically different from the similarity within species. This indicates that the interactions of plants and pulp-eating birds are little specialized. Interspecific differences in most fruit traits (including color, pulp composition, etc.) probably do not generally result in great or predictable differences in avian fruit consumers.