Role of ants as dispersers of native and exotic seeds in an understudied dryland

Abstract

1. Seed dispersal by ants, i.e. myrmecochory, is important in drylands because ants may contribute to overcoming the typical resource limitation imposed on plants in these environments. Dispersal distance and directed dispersal of seeds to nutrient-enriched ant nests benefit plants by reducing parent or sibling competition and improving growth, survival, and reproduction. 2. This study investigated the role of ants as seed dispersers in the semi-arid Patagonian steppe. In particular, this study surveyed native and exotic plants potentially dispersed by ants (i.e. those with nutritive tissues attached to seeds that could attract ants), identified seed disperser ants, and compared their effectiveness as dispersers (i.e. number of removed seeds, transport distance, and seed fate). 3. It was found that 9% of plant species could be potentially dispersed by ants, and field experiments were carried out with five of them (three natives and two exotics). Six ant species dispersed seeds, with Dorymyrmex tener being the most effective seed disperser, interacting preferably with an exotic seed. Finally, the types of nutritive tissues of the seeds are important in determining the attractiveness towards different ant foraging groups. 4. This study's results highlight that ant foraging group and seed's nutritive tissues are relevant traits that could help in understanding ant–seed interactions. Furthermore, in the Patagonian steppe, there are effective seed disperser ants that could play an important role in the distribution of native plants, as well as the spread of invasive species, being especially relevant in nutrient-poor drylands due to the benefits provided by myrmecochory.