Thorny questions (my guess)

Robin Leech robinl at CONNECT.AB.CA
Tue May 16 16:33:40 CDT 2000


And I note that there are few thorny things in the Arctic and Subarctic
floral areas.  And there are not that many grasses relative to dicots up
there, either.  And there are relatively few species of grazers in the
Arctic - muskox, hares, lemmings, caribou mainly, and not very many of them
over wide areas.

Mebbe my old timer's disease is catching up with me, but I do not recall as
many thorny things in Australia as I do recall in Africa amongst the
Acacia-type trees.  Dorn oder Stachel - long prickly ones, short ones,
wait-a-bit ones, you name it, Africa had them.   It occurs to me that hooved
animals could stand to walk without problems among dropped thorns much
better than could soft-pawed marsupials.  Let the ideas flow.
Robin Leech

----- Original Message -----
From: "Panza, Robin" <PanzaR at CARNEGIEMUSEUMS.ORG>
To: <TAXACOM at USOBI.ORG>
Sent: Tuesday, May 16, 2000 3:37 PM
Subject: Re: Thorny questions (my guess)


> >>>>>
> 1)  Why are thorny plants more abundant in savannas and areas like the
> Black Belt than elsewhere?
> 2)  If thorns were an adaptation against Pleistocene and earlier browsers,
> what kept these browsers from going into habitats where plants were less
> thorny?  Why wouldn't other plants outside savannas develop thorniness as
a
> defense against these browsers.
> <<<<<
>
> My *guess* would be that it has to do with the competition (grass).  Grass
> is not a great source of animal nutrition, relative to the effort.  Any
> dicots in a sea of grass would seem to be pretty prime food.  By
definition,
> there are relatively few dicots in a grassland, so there are few plants
> "sharing the load" of vertebrate predation, so to speak.  That's pretty
> strong selection for anti-predator tactics.
>
> One dicot species surrounded by other dicots (in a woodland, say) has much
> lower risk of debilitation or death from predation, so there's less
> selective advantage to using its resources for strong woody projections.
>
> just the 2 cents of a zoologist,
> Robin
>
> Robin K Panza                         panzar at carnegiemuseums.org
> Collection Manager, Section of Birds          ph:  412-622-3255
> Carnegie Museum of Natural History       fax: 412-622-8837
> 4400 Forbes Ave.
> Pittsburgh  PA  15213-4008  USA
>




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