Size of the overwintering monarch populations - published data.

Stanley A. Gorodenski stan_gorodenski at
Tue Oct 14 12:39:46 EDT 2003

Notwithstanding the fact that "There is no clear cut minimum effective 
population size that leads to inability to evolve or to mutational 
meltdown" as Patrick stated (I arbitrarily chose 5,000 for illustration 
purposes, but purposely chose not to use the term 'mutational meltdown') 
I still think a study pursuing the general idea I outlined would be an 
interesting project. We could learn more about the dynamics of this 
butterfly, and it would provide additional research topics (including 
theoretical population genetic topics) for graduate students and post 
docs.  :-)  

Some readers on this list may not have read all the way through my 
message and therefore did not get to the last paragraph. After reading 
it myself  I see it could have been written with better clarity. I had 
some questions at the end that I do not expect an answer to but would 
like to raise them again. They immediately follow. To them I want to add 
two more:
1. I assumed 400 local populations for illustration purposes, but what 
do we know about how many local populations might exist as a result of 
geographic barriers or neighborhood size considerations?
2. As important as it is to determine the size of the returning 
population (which Brower is focusing on), it is also important, from my 
perspective, to know how many make it back and reproduce. What do we 
know about this from tag counts?
3. It is widely recognized that the Monarch is a 'widely outbreeding' 
species as Patrick said. But how certain can we be of the degree of it? 
If  the Monarchs on their return randomly distribute themselves over the 
northern attitudes, then there would indeed be a large degree of 
outbreeding, but if they generally go back to the same area they 
emigrated from, the outbreeding would not be as large as we think.

Some of the answers to these questions may be already common knowledge 
amongst those studying the Monarch. I do not know that much about 
Monarchs, but if I were to get into studying them there sure would be a 
lot to learn.

> What do we know about the return distribution of Monarchs? Are there 
> any tag counts of returning butterflies to determine if they return to 
> the same area, or generally the same area? I recall reading on this 
> list of an indication from some research that some geographic 
> differentiation was taking place. Not knowing more about this 
> research, it could indicate Monarchs are returning pretty close to the 
> areas from which they emigrated.


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