From: gil@tillage.DIALix.oz.au (Gil Hardwick)
Newsgroups: sci.environment
Subject: Temperate zone habitat loss
Date: 24 Jan 93 04:37:20 GMT
Organization: STAFF STRATEGIES - Anthropologists & Training Agents


In article <149180335@hpindda.cup.hp.com> alanm@hpindda.cup.hp.com writes:

 > Island biogeography is a theory which attempts to explain observed species
 > area relationships in terms of processes of immigration, extinction and
 > saturation. This theory is applicable in mainlands since at some level of
 > resolution habitat islands are ubiquitous -- they are not synonomous with
 > oceanic islands. The fact that the theory can be applied does not mean that
 > a single species-area curve holds everywhere *that* the theory can be applied.
 > It means that the same underlying biogeographic processes are at work producing
 > the various curves.

Would you accept, then, that each of these "islands" represents a
unique environment, the model also therefore applicable to human
ethnic/dialectal groups?

 > As Andrew Taylor pointed out, my remark that diversity and endemism tend
 > to increase towards the tropics is just a biogeographic fact, having nothing
 > to do with the applicability of a particular species-area relation.

Would this explain also the increasing linguistic/dialectal diversity
among human populations towards the tropic?

 > Like all models in science, models of MVP (minimum viable population) involve
 > omission of more details than they include, and are not overthrown simply
 > by pointing out that something has been omitted. Instead, what this means is
 > that a multiplicity of models, abstracting different aspects of reality, have
 > to be considered to understand any natural phenomenon. MVP is no exception.
 > It results from genetic factors, breeding biology, and environmental fluctation
 > acting together. The MVP when all these factors are taken together -- the
 > one which should be the basis for a conservation policy for that population 
 > -- is increasingly thought to be set mainly by environmental fluctuation 
 > rather than by genetics. However the MVP for the *specific* kind of genetic 
 > information I mentioned (neutral variation), considered in isolation from 
 > other factors, can be determined by the criterion that Ne >> (1/2u), where 
 > u is the mutation rate of the variation and Ne is effective population size. 

Do you see, for some reason, that human populations *differ* in some
marked or extra-ordinary way from basic conformity with this analysis?

 > By "MVP" in this case I mean the minimum size for persistance, not against 
 > population extinction, but just of population polymorphism. The result is 
 > robust and can be derived in numerous ways, both by starting with diffusion 
 > models of genetic drift and by simpler means (one of which I gave in ECO 
 > CENTRAL 24, I think it was). Derivations can be found in any standard text 
 > on population genetics. The result is also experimentally very well confirmed
 > by electrophoretic measurements of single-locus polymorphism in Drosophila 
 > and other species, demonstrating that what was left out of consideration when
 > the model was formed nevertheless left a phenomenon of importance behind. 
 > [This is how real science is done -- not by aprioristic rejection of ideas 
 > for failure to achieve instant universality, but by creative construction 
 > of ideas that can survive observation and experiment in some insight-producing
 > area of application. Universality is *extremely* elusive in biology. But 
 > universality is not at all the same thing as *understanding*.]

Indeed! Now, what would explain such elusiveness? Insufficient data?
Or after 120 years of biologists working all over the world as *yet*
unable to supply proof, simply a fundamental flaw in the whole theory
of universality?

 > A fairly large amount of neutral polymorphism can probably be lost in any 
                                .
                                .
                                .
       [rest goes off into more purely biological discussion]
                                .
                                .

Gil
Xref: sparky sci.environment:14717 ca.environment:1193 ba.transportation:3174