Mucilage-binding to ground protects seeds of many plants from harvester ants: a functional investigation

The seeds of many plant species produce mucilage on their surfaces that when wetted and dried, firmly adheres seeds to surfaces and substrates. Previous studies have demonstrated that seed anchorage to the ground can reduce seed predation, though only a few species have thus far been tested.

Here we investigated whether binding to the ground reduces seed removal by harvester ants (Pogonomyrmex subdentatus), an important granivore, for 53 species with mucilaginous seeds. We also explored functional traits that associate with seed removal risk to understand the ecological and evolutionary context of this granivory resistance trait.

Using a field cafeteria choice experiment, we compared harvester ant seed removal of wetted ground-bound seeds to dry unbound control seeds for these 53 species. In the lab, we developed a simple assay to score dislodgement force. We examined whether this force, seed mass, and seed mucilage production explained the interspecific variation in protection th...