Kin Selection in Plants, a bit off topic

Joe Shaw
Wed, 13 Jun 2007 17:52:50 PDT
Hi Gang,

Kin Selection and Inclusive Fitness are important and not completely 
understood aspects of evolution.  The general idea is that natural selection 
may favor traits that help relatives of an individual to survive.  The 
reasoning is that relatives (kin) share some of the genes that an individual 
has, and that helping kin can help perpetuate shared genes.

Inclusive Fitness is apparently not the same as Altruism, but the concepts 
are similar and overlapping.  Helping kin has costs, and Altruism has costs. 
If an organism shares resources (nutrients, water, sunlight) there is 
typically a cost.  Sharing sunlight or soil nutrients can result in 
production of fewer flowers and seeds, and therefore fewer offspring.  Loss 
of offspring is the ultimate cost.

Therefore, whenever Inclusive Fitness is observed, it is proposed that there 
is some sort of evolutionary tradeoff, a mitigation of cost.  An individual 
might produce fewer direct offspring, but kin have nearly identical gene 
sets and a benefit can be realized (in evolutionary terms) if kin are able 
to propagate and so perpetuate identical (or similar) genes.

The interesting bit of news this week is that Dr. Susan Dudley and her 
colleagues at McMaster University have documented that plants seem to give a 
break to members of their own species in the never ending competition for 
resources.  The effect was observed in root growth.  Typically, plants will 
make extra roots if they are in proximity to other plants.  The extra roots 
help a plant acquire water and nutrients that might otherwise be usurped by 

Dr. Dudley has shown that plants produce more roots (and do so more quickly) 
when in proximity to unrelated plants.   When grown alongside siblings (same 
maternal line) the study plants produced fewer roots--the plants shared. 
This is all interpreted is Kin Selection, i.e., the plants are not as 
competitive with relatives as they are with strangers.

The experiments were conducted in the laboratory where plants (Cakile 
edentula) were grown in groups of four.  The Cakile were grown with same 
species (derived from the same maternal line) or with more distantly related 

The result is more than a bit of data showing the kin selection is a broad 
phenomenon in Nature.  The result raises really interesting questions.  How 
do plants recognize close relatives vs. not close relatives and how do the 
modulate their root growth accordingly.  The answer will be interesting to 
unravel; perhaps the mechanism is related to pollen acceptance or rejection 
wherein plants can recognize their own pollen and prevent 
self-fertilization.  Perhaps an unknown mechanism is involved such as 
related plants being able to share mycorrhizal fungi and perhaps gain by 

If one plant species has Kin Selection it seems most probable that other 
species will have the feature.  I'm confident that some bulbs will be shown 
to exhibit Kin Selection.

LINK:  Dr. Dudley, Home Page, McMaster Univ.…

LINK:  Page 1, The Ecology of Kin Recognition (JSTOR)


Conroe, TX 

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