Checkerspot on the news

[Neil Jones]

In article <3917ABDF.7BC338F9 at helsinki.fi>
           niklas.wahlberg at helsinki.fi "Niklas Wahlberg" writes:

Thanks for making these points they are very useful.


> Dear Leps-Listers,
>   To continue on the metapopulation theme, I would like to remind you
> that the spatial population structure of a species is not constant over
> its range. For instance the species that has been discussed in this
> thread (Euphydryas editha) has a so-called "mainland-island" population
> structure in the San Fransisco area (as was discussed by John and
> Patrick), whereas in the Sierra Nevada mountains the same species
> (albeit a different subspecies) has a more classical metapopulation
> structure (Thomas and Singer 1998). The main implication of this is that
> one can't really generalize _even within the same species_ without
> taking into account the local landscape structure.
>   Also touting numbers derived from models is not a good idea in
> practical conservation. Models allow us to get crucial insights into how
> Nature works, but the bottom line is that they are (usually extreme)
> simplifications of what really happens. This means that some factors
> that might have a large effect on the dynamics of natural populations
> may be missed out or wrongly modelled.

Yes, Of course the numbers are not exact. I was wrong not to have followed
the simplification with the proviso that the models specified an exacting
and "perfect" case which will differ in real life. This is due to things we
cannot allow for. I usually do when I am explaining it to people as I did the
last time I quoted it here.
I try to put things so that the ordinary layman lepidopterist, who is not
into reading long complicated books and papers full of mathematics, can 
understand them. "3 times the Square root" is problably complicated enough.
It is not that people are stupid it is just that mathematics can frighten
people.
I regularly have to get this point across to keen naturalists who don't
have a background in  mathematics so I try to put it simply.
To give you an example which I might have mentioned before. I was once
trying to convince a British Planning Inspector about the need to conserve
empty habitat patches. He was deciding on the building of a new
road which might impact on the habitat of  the Marsh Fritillary.
E. aurinia. I used the single equation  dP/dt=cP(1-p)-eP.

His repsonse was to ask in a "posh educated" voice.
"Is that an equals sign or a proportional to sign?" 


> The best example that is still
> hanging is how to incorporate environmental stochasticity into our
> models. We all know that the meteorologists have difficulties in
> predicting the weather next month, so how can we rely on the
> quantitative predictions of our models that are usually run for hundreds
> or thousands of "generations"?!
>    Nevertheless, I think that the concept of metapopulations has brought
> much to conservation. A good rule of thumb is that suitable habitat that
> does not have a certain species is as important as habitat that does
> have the species. We've been studying a relative of E. editha, Melitaea
> cinxia, for the past 7 years here in Finland. In a patch network of
> several thousand suitable habitat patches there have been several
> hundred local populations each year. All but a handful have gone extinct
> _at least_ once during the study period (read all about it in Hanski
> 1999, Metapopulation Ecology.). This, I think, underlines the importance
> of habitat that is empty today. It might not be tomorrow.
> 
> Cheers,
> Niklas

Yes, That is exactly what I was saying empty habitat MUST be conserved.
Thanks for putting this argument across. It is VERY important.


-- 
Neil Jones- Neil at nwjones.demon.co.uk http://www.nwjones.demon.co.uk/
"At some point I had to stand up and be counted. Who speaks for the
butterflies?" Andrew Lees - The quotation on his memorial at Crymlyn Bog
National Nature Reserve