11 June 2009

When plant siblings play nice, everyone loses

ResearchBlogging.orgA couple years ago, scientists studying the wildflower American searocket, noticed something funny: when grown in the same pot with sibling seeds, searocket plants grew smaller roots than they did when sharing a pot with unrelated plants. It looked as though searocket plants recognized their siblings, and tried not to compete with them.

If this were a widespread phenomenon, it could dramatically change how biologists think about plant's evolution and ecology. Right now, we think that the huge diversity of seed dispersal mechanisms -- from fruit, to ballistics, to ants -- evolved at least in part to minimize competition between sibling plants. But if plants can recognize and preferentially accommodate their siblings, clusters of related plants might actually improve their collective fitness -- or rather the fitness of the genes they share.

Lupinus angustifolius
Photo by enbodenumer.
A new paper in Proc. R. Soc. aims to test the hypothesis that sibling recognition boosts plants' collective fitness. The authors conducted a more precise version of the original kin recognition experiment, planting seeds from common European lupines (Lupinus angustifolius, pictured) alongside their siblings, unrelated seeds from the same source population, or unrelated seeds from a distant population. They then measured a variety of fitness traits to determine whether individual plants benefited from growing near siblings, or whether sibling groups performed better collectively than groups of unrelated competitors.

The results were pretty clear -- in staying out of each other's way, sibling plants had lower individual and group fitness. Plants growing near siblings produced fewer fruits and seeds than those growing near non-relatives, and groups of siblings collectively produced fewer fruits and seeds than groups of unrelated plants. This suggests that the kin recognition effect may actually contribute to selection for better seed dispersal, rather than provide a benefit for growing together.


Dudley, S., & File, A. (2007). Kin recognition in an annual plant. Biology Letters, 3 (4), 435-8 DOI: 10.1098/rsbl.2007.0232

Milla, R., Forero, D., Escudero, A., & Iriondo, J. (2009). Growing with siblings: A common ground for cooperation or for fiercer competition among plants? Proc. R. Soc. B, 276 (1667), 2531-40 DOI: 10.1098/rspb.2009.0369

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