Are there "Identical Twin" plants?

Jacqueline Dyer jd6 at soas.ac.uk
Sun Dec 17 14:09:45 EST 2000


Dear George

Unfortunately for you, your hypothesis isn't your hypothesis, but a well 
known fact: ANY genotype of ANY species is overwhelmingly likely to exhibit 
phenotypic variation depending on what environment it is raised in. This is 
known as PHENOTYPIC PLASTICITY - what happens is that different genes get 
EXPRESSED depending on the environment. For example, exactly the same 
genotype of some plants can produce a completely different looking plant 
depending on the environment it happens to grow in - not just different 
size, but such different phsyiognomy that it would not be recognisable to 
the inexpert eye as the same species, let alone the identical genotype.

Another thing you have to realise is that being big is not an advantage if 
it means, for example, that you stick out and are therefore more likely to 
get eaten. If your environment doesn't include a key predator (that is, a 
herbivore if you are a plant) then being big might have advantages, like 
maybe you are better able to compete for light, but if there are herbivores 
around, it may be best to stay small. The small plant should not be 
considered to have a 'growth deficit' - its size is optimal for its 
environment, which happens to include herbivores. You could argue that an 
environment with herbivores is a sub-optimal environment for the plant, its 
ideal environment being one without herbivores, but the same argument would 
apply to an environment without competitors, in which there was no 
advantage to being big!  Adaptation is all about overcoming constraints and 
being big is  just one solution to a number of problems. Being small is 
equally a solution to a different set of problems. THERE IS NO SUCH THING 
AS AN IDEAL TYPE THAT IS NOT RELATIVE TO A GIVEN ENVIRONMENT.



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