I've never seen the niche defined as just a physical space. Hutchinson referred to "multidimensional hyperspace" and, setting aside the jargon aspects, what this means is that the niche includes temperature ranges, salinity ranges, moisture, food, etc. A species normally occupies the same niche in different ecosystems, e.g. marine organisms may be found in different water bodies but always within the same temperature and salinity ranges.
Bill Silvert ----- Original Message ----- From: "Malcolm McCallum" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Friday, November 23, 2007 3:44 PM Subject: Re: "unoccupied" niches and 'coppetitive exclusion" >I agree with Hilmy that a niche is more than just a physical space, I > think of a niche in "functional" terms more than "geographical." The > niche is its "fuctional space in a particular ecosystem." Any given > species may occupy different niches within different ecosystems, and there > is typically much niche redundancy in which some species in a given > ecosystem are dominant during certain conditions whereas when conditions > change in that same ecosystem (drought vs wet years for example) other > species may prevail. Despite this, even within a said set of conditions, > a high degree of redundancy should prevail, especially for producers, > grazers, and decomposers. there tends to be minimal redundancy at higher > levels such as tertiary consumers.
