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At 06:48 AM 21/05/01 -0400, John Bois wrote:
I think this was _my_ point.  Others are arguing that opossum radiation in
NA shows they are competitive with placentals.  But, if man has disturbed
the environment so much that competition doesn't occur, this argument is
nullified. (I reiterate that I would not be surprised if the opossum were
fully competitive or even superior in specific niches)

Then what is the point? How many species are competitive in all niches? The fact remains that the opossum has expanded its range and numbers considerably in North America at the same time as placental species with similar tendencies have also increased in human-disturbed areas (eg raccoons, foxes, skunks, even Norway rats). Didelphis opossums are very common in South America, as are many other species despite the presence of placentals of many species that could be potential competitors (including primates, procyonids and rodents). There is no evidence AT ALL that these species are being "outcompeted" by any placental that I am aware of.

John seems to be reasoning teleologically: he has decided that all marsupials are "inferior" to all placentals, therefore opossums must be unable to compete with placentals no matter what the facts say. This is in the same category as the Feduccia argument that dino integument can't be feathers because there are no feathered dinos, dammit....

Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2 mailto:ornstn@home.com