what is a species

[Michael.Chamberland]

> From:         John Trueman <trueman at RSBS-CENTRAL.ANU.EDU.AU>
> In response to my suggestion re conceptualising species as sets of
> populations having "a separate evolutionary future", Richard Jensen asked
> >What about "minimally diagnosable entities"?
>
> That is a good question!  I see three problems with the use of 'minimally
> diagnosable entity' as a species concept or in species diagnoses:
>
> First, many diagnosable entities ought not to be called species.
> Daschund/greyhound might be one example.
>
> Second, diagnosability results from the past aquisition of differences but
> says nothing about whether those differences will persist.  One reason why
> daschunds and greyhounds ought not to be considered two separate species is
> that although their separate pasts result in present differences there is a
> reasonable expectation that, over evolutionary time, they are going to
> share a common future.

I have difficulty with making assumptions about a taxon's evolutionary
future.  Given the wide-scale destrution and alteration of habitats
around the world, I think we can rarely assume that a species will continue
to evolve "naturally".  Evolution seems now more likely to favor those taxa
which can redily adapt to disturbance, or those which are "lucky" enough to
get a ride to a new habitat lacking natural controls (ie. Opuntia in
Australia, or gypsy moth in New England).  These twists of fate cannot be
easily predicted.

This raises a question I've been wondering about.  If a plant is extinct in
the wild (habitat gone, pollinators lost or unknown), but this plant is
maintained in cultivation... is it still a "species"?  Or is it now better
considered a cultivar, even though the morphology was shaped by natural
selection rather than by artificial selection?

Michael Chamberland