MadSci Network: Zoology

Re: is there a case for a separate subspecies of urban vulpes vulpes?

Date: Mon Jan 8 06:12:45 2001
Posted By: Will Higgs, Grad student, Zooarchaeology, University of York
Area of science: Zoology
ID: 978689852.Zo


I'm afraid I am not Dr Susman, but I will do my best !

Urban foxes certainly look different from 'wild' ones, although it is worth 
remembering that all land in this overcrowded country is managed to some 
extent, so it is questionable whether there are any genuinely 'wild' 
animals !  I think they look different because they are living in a very 
different environment from the wild ones.  Urban foxes often live at much 
higher densities than is natural, resulting in raised levels of stress from 
many factors, especially increased levels of disease and parasites.

Certainly, populations of animals living in different environments are 
subjected to different selective pressures, and will diverge genetically 
until they become separate subspecies, or even species.  However, each city 
has its own population of foxes, so each might become a separate 
subspecies.  This is unlikely because the populations are small and 
unstable, for instance the population of foxes in Bristol became virtually 
extinct after reaching a very high density, due to an epidemic of mange.

In this event, the population will probably be replaced by foxes from 
outside the city, and any genetic uniqueness will be lost.  Even if the fox 
population of a city does not crash, there will be continuous gene flow 
across the boundary between urban and wild foxes, preventing the isolation 
of a genetically unique sub-population.

So - to answer your question, yes, I do think the environmental differences 
between the inside and outside of a city are great enough to drive 
evolutionary change, but I don't think it will happen because populations 
of city foxes are too small and unstable.

I looked up the taxonomy of foxes in Corbet & Harris - The Handbook of 
British Mammals, 3rd edition, and it has been suggested that Scottish foxes 
should be a separate subspecies because they are larger than English ones. 
This suggestion was rejected (I'm not sure who by !) and they go on to 
discuss whether British foxes should be a different subspecies from 
European, or a different species from N American - etc.  Basically, if you 
compare any two populations of animals, you will find differences.  Home 
counties humans are an obvious case in point, but the question is - at what 
point do the differences become great enough to justify creation of a 
subspecies ?  The answer, as with that old chestnut 'What is a species ?' 
is 'What a good taxonomist says it is'.

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