My view of a niche is similar, except I imagine them in terms of jobs =20= or occupations needed to fill a particular role in the environment. =20 For example "someone" needs to clear up dead animals, but the job =20 description (or niche description) will be variable in terms of =20 habitat, part of the animal needing broken down etc.
Or a slightly different example would be weasels and stoats in the =20 British Isles where there is obviously a niche (or job) for a small =20 long bodied predator. In the UK this is filled by stoats and weasel, =20 but in Ireland it is filled only by stoats. But the stoats in Ireland =20= have a wider range of body sizes that cover roughly the same size =20 range covered by the two species in the UK. So in the Ireland =20 circumstances have created a niche filled by one species where the UK =20= two niches have evolved. Maybe too simplistic and anthropomorphic for many, but I find it =20 useful as an initial concept when students are struggling with the =20 idea of niche and seem to think its another name for a habitat or a =20 physical place. Graham Graham Smith [EMAIL PROTECTED] On 24 Nov 2007, at 04:11, Osmar Luiz Jr wrote: > Well, I usually don't think in the niche as some sort of "entity" =20 > like some > people do. > > > > In my vision, the niche is a set of opportunities that an organism =20 > is able > to explore. It can be constrained in part by the conditions offered =20= > 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 =20= > 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 =20 > condition > driven speciation, but by the other hand there are examples of mass > extinctions of entire clades that could not adapt its morphologies =20 > to new > environmental conditions. Determine when one factor is more =20 > important than > other is a way to assume this dual facet of the niche and may =20 > 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 =20= >> the >> niche >> define the species? David seems to be saying that the species =20 >> defines the >> niche and Bill seems to be arguing that the niche exists =20 >> 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 =20 >> general >> definition is more useful. For example, if a species becomes =20 >> extinct, does >> its niche vanish with it? Since generally something will replace =20 >> it, it >> makes sense to describe the displacing species as moving into a =20 >> vacant >> niche. >> >> Of course the new species may have a somewhat different niche, but =20= >> I think >> of a niche as similar to an apartment -- new occupants my move the =20= >> walls >> and >> make some changes, but basically they occupy the same space. >> >> Unfortunately any attempt to generalise the niche concept runs =20 >> into the >> philosophy that definitions should never change. I have written =20 >> about the >> niche as a fuzzy set for example (which is basically what you see =20 >> 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 =3D93niche=3D94 is very much defined around a = specific =3D >>> species- the >>> term itself is something of a misnomer in ecological terms =20 >>> because we =3D >>> assume >>> the traditional noun to describe a physical space or an element of =3D= >>> habitat, >>> or in the argument of some posted here, a set of >>> habitat/ecosystem/geographical parameters that are independent of =20= >>> the >>> species itself as though somehow =3D93vacant=3D94, yet the term as I = =20 >>> have =3D >>> always >>> understood it to be refers more accurately to the way in which a =3D >>> particular >>> organism fits into the ecosystem... >> >> Esta mensagem foi verificada pelo E-mail Protegido Terra. >> Scan engine: McAfee VirusScan / Atualizado em 23/11/2007 / Vers=E3o: >> 5.1.00/5170 >> Proteja o seu e-mail Terra: http://mail.terra.com.br/ >> >> >> >> --=20 >> 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 >> >>
