co-evolution

David Haas dhaas at CHI1.UNCFSU.EDU
Mon Apr 22 11:50:29 EST 1996


Dear Plant-eders,

   The other day I showed my botany class part of the Private Life of 
Plants video on flowers and pollinators.   There was a part 
where a hover fly with an extremely long proboscis was visiting 
flowers with extremely long corollas.  I explained how this was an 
example of co-evolution where the population of hover flies through 
natural selection evoleved long proboscises to reach the nectar 
and the flowers long corollas accomodate the insect.
 
   This situatuation seems to suggest  a positive feed back loop where 
long proboscises select for long corollas and long corollas for long 
proboscises.  I can see how  long proboscised flies would have an 
advantage over short proboscised flies by being able to obtain more 
nectar and  thus more offspring but what about the flowers?  Why would 
longer corollas be selected for?   Is it exclusively  the hover flies  doing the
 selecting or is it  possibly other pollinators which are able to remove nectar
 without pollinating the smaller corollaed flowers?   Any thoughts?


Dave Haas  



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