Myrmecochory is seed dispersal by ants. ~23,000 plant species bribe ants to take their seeds by coating them with elaiosomes: fleshy seed caps rich in lipids and proteins. Ants cart such seeds to their nest and serve the elaiosome to their larvae.
Plants compete for ant services. Ants prefer larger seeds to smaller ones, so small-seed plants release their seeds in early spring, when ant foraging is unreliable. This advance release avoids competition from large seeds, which are let go later, when ant populations are at their peak.
The fatty acid content, particularly oleic acid, is the main trigger to prompt ant seed pickup.
Plants know what nourishes ant larvae. Some target their elaiosome content to entice specific ants, thus enhancing their fitness by choosing the most effective dispersers.
Some plants cheat, by coating their seeds with enough temptation to be taken, but not provide the ants with nutritious food. Puschkinia and Hepatica are exemplary myrmecochory cheaters.