Family Tree?


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By Elsa Youngsteadt
Photo by Carsten Niehaus

Plants can tell when they're growing in a pot with their siblings rather than strangers, according to a new study by biologists from McMaster university. And they're nicer to their relatives. That is, when they're growing with family, they don't put so much energy into growing roots to outcompete the neighbors for water and nutrients. Kin recognition has been previously demonstrated only in animals.

The biologists discovered kin recognition in plants by growing groups of Great Lakes sea rocket (Cakile edentula) plants in groups of four-- consisting of siblings from the same mother, or with offspring of all different mothers. The plants growing with relatives were less competitive. Because they invested less energy growing extra roots to compete with neighbors, they may have had more energy left over for flowering and reproduction. This could explain why, in nature, groups of sibling rocket plants growing together have a higher reproductive output than groups of strangers.

From the evolutionary perspective of getting one's genes into the next generation, it could be counterproductive for siblings to compete-- since they have so many genes in common. Sibling groups should maximize their overall reproductive output-- their so called inclusive fitness-- rather than that of a single individual. On the other hand, there would be no evolutionary advantage to sharing resources with distantly related strangers. In this case, a plant would get more of its own genes into the next generation by trying to outcompete the neighbors rather than risk having them use resources that it could be applying to its own reproductive output.


Original article in Biology Letters (open access!)

News release from McMaster University story

Explanation of kin selection

Questions for review and discussion

1. What experiment did the researchers use to test whether the plants could tell if they were growing with siblings or strangers?

2. How is root allocation related to competition? To reproductive fitness?

3. Define kin selection. How does this study in plants relate to the theory of kin selection?

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