Seed dispersal by ants: are seed preferences influenced by foraging strategies or historical constraints?

Abstract

Summary The objective of this study was to quantify preferences of ants for seeds of different plant species and to test if these preferences were caused by foraging strategies or by historical constraints. We compared seed removal rates of ten different ant-dispersed plant species found in temperate forests, along forest edges and in grassland. We found significant differences in seed removal rates among the ten species. To test if these differences were caused by foraging strategies we examined the relationship between seed and elaiosome size and seed removal rate. We found that seeds with larger elaiosomes had significantly higher removal rates. To test the historical constraint hypothesis we investigated whether plants from forest, forest edge or grassland habitats were preferred by ant species found in the same habitat type. If historical constraints exist we would expect that ants remove preferentially the seeds of plant species which they are used to handle in the course of their phylogenetic and ontogenetic history. In contrast to this prediction, we found that plants of a certain habitat type were in general not preferred by ants of the same habitat type. These results demonstrate that seed preferences of ants are mainly determined by foraging strategies and not by historical constraints.