Elaiosomes

Elaiosomes are lipid-rich structures attached to the seeds of many plant species. The term elaiosome comes from Greek elaios, oil, and soma, body, reflecting their oily composition. These seed appendages are typically fleshy and vary in size and shape; in many taxa they arise from tissues associated with the seed coat or funiculus.

The primary function of elaiosomes is to attract ants, a dispersal strategy known as myrmecochory. Ants feed on the fatty tissues of the elaiosome and then transport the seed to their nest. There the elaiosome is consumed, and the seed is discarded, often in a nutrient-rich cache or midden, which can enhance germination conditions. This mechanism promotes distance dispersal, reduces seed predation by other animals, and can place seeds in favorable microhabitats for growth.

Elaiosomes are common in temperate and tropical regions and occur across a variety of plant groups. They have evolved multiple times in different lineages, contributing to the ecological role of ants in plant communities. In some ecosystems, myrmecochory influences plant distribution and recruitment patterns, aiding seeds in overcoming challenges such as unsuitable microhabitats near the parent plant.

Evolutionary notes indicate a coevolved relationship between plants bearing elaiosomes and local ant species. While many species rely on elaiosomes for dispersal, others lack such structures and employ alternative strategies. In some taxa, the composition or presence of elaiosomes can affect ant behavior and seed fate. Viability and germination outcomes can vary with species and environmental conditions.