Ant dispersal in Aristolochia serpentaria (Virginia snakeroot)

Myrmecochory, the dispersal of seeds by ants, is a common adaptation among perennials growing in mesic forests, and the principal characteristic of seeds dispersed by ants is the development of the elaiosome, an oily, nutritive appendage that is attractive to ants. Allard (2002:4) reported that the seeds of Aristolochia serpentaria did not exhibit any specialized adaptations for dispersal and that they lacked an elaiosome. However, neither statement is correct as is indicated in the above photograph of a recently opened capsule of Aristolochia serpentaria. Note that the seeds are attractive to ants and that each seed is provided with a large, creamy-white, fleshy elaiosome. Although seemingly small relative to the size of the seeds, these ants were eventually able to remove all but one of the seeds from the capsule.

Dried Aristolochia serpentaria seeds, as might appear on an herbarium sheet, do not display signs of an elaiosome, which in this case quickly dries and shrivels up. It is thus easy to conclude that Aristolochia serpentaria is not adapted for dispersal by ants; however, the cultivation of this plant in pots, which makes very close observation possible, reveals myrmecochory and adds Aristolochia serpentaria to the long list of forest wildflowers with ant-dispersed seeds.

Reference:

Allard, D.J. 2002. Aristolochia serpentaria L. (Virginia Snakeroot) Conservation and Research Plan for New England. Framingham, Massachusetts: New England Wild Flower Societ. Retrieved on 8 August 2010 from http://www.newfs.org/docs/pdf/Aristolochiaserpentaria.pdf.

© 2010 Rufino Osorio.