Well, I usually don't think in the niche as some sort of "entity" like some people do.
In my vision, the niche is a set of opportunities that an organism is able to explore. It can be constrained in part by the conditions offered by the environment and part by the phylogenetic restrictions of the organism. In this way, the niche in neither pre-defined by the environment or by the organism, but by a conjunction of both. Of course, we have a lot of examples of convergent evolution in quite non-related taxons that lead us to assume some defined particular condition driven speciation, but by the other hand there are examples of mass extinctions of entire clades that could not adapt its morphologies to new environmental conditions. Determine when one factor is more important than other is a way to assume this dual facet of the niche and may render better conclusions than keep trying to find rigid theoretical definitions. apologizes for the english Osmar Luiz Jr. Brazil ----- Original Message ----- From: "Warren W. Aney" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Friday, November 23, 2007 4:18 PM Subject: Re: "unoccupied" niches and 'competitive exclusion" > Does the species define the niche? Or (in evolutionary terms) does the > niche > define the species? David seems to be saying that the species defines the > niche and Bill seems to be arguing that the niche exists independent of > the > species filling it. Did Darwin's Galapagos finches evolve to fit > pre-existing niches, or did they define the niche as they evolved? > > Warren W. Aney > Tigard, Oregon > > -----Original Message----- > From: Ecological Society of America: grants, jobs, news > [mailto:[EMAIL PROTECTED] Behalf Of William Silvert > Sent: Friday, November 23, 2007 1:31 AM > To: [email protected] > Subject: Re: "unoccupied" niches and 'coppetitive exclusion" > > > This is how Hutchinson defined it, and his disciples have blocked any > attempt to generalise the term, but many of us feel that a more general > definition is more useful. For example, if a species becomes extinct, does > its niche vanish with it? Since generally something will replace it, it > makes sense to describe the displacing species as moving into a vacant > niche. > > Of course the new species may have a somewhat different niche, but I think > of a niche as similar to an apartment -- new occupants my move the walls > and > make some changes, but basically they occupy the same space. > > Unfortunately any attempt to generalise the niche concept runs into the > philosophy that definitions should never change. I have written about the > niche as a fuzzy set for example (which is basically what you see in any > book on niche packing even though they don't use the word), but since > Hutchinson didn't use the word fuzzy, the concept is verboten. > > Bill Silvert > > > ----- Original Message ----- > From: "David Hilmy" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Friday, November 23, 2007 4:25 AM > Subject: Re: "unoccupied" niches and 'coppetitive exclusion" > > >> The concept of =93niche=94 is very much defined around a specific = >> species- the >> term itself is something of a misnomer in ecological terms because we = >> assume >> the traditional noun to describe a physical space or an element of = >> habitat, >> or in the argument of some posted here, a set of >> habitat/ecosystem/geographical parameters that are independent of the >> species itself as though somehow =93vacant=94, yet the term as I have = >> always >> understood it to be refers more accurately to the way in which a = >> particular >> organism fits into the ecosystem... > > Esta mensagem foi verificada pelo E-mail Protegido Terra. > Scan engine: McAfee VirusScan / Atualizado em 23/11/2007 / Versão: > 5.1.00/5170 > Proteja o seu e-mail Terra: http://mail.terra.com.br/ > > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.503 / Virus Database: 269.16.4/1147 - Release Date: > 23/11/2007 09:19 > >
