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- the evolutionary adaptations that the organism (not the space) has acquired in terms of behavior, morphology, physiology, etc. And so no two species can indeed share the exact same niche, and even if two species shared almost identical ecological = features, the principle of competitive exclusion would apply- in the case of = invasive aliens, quite often =93generalists=94, the advantage in terms of feeding = and then reproducing is taken by the interloper. The term =93niche=94 is = therefore better described as =93functional niche=94 (as in the early work of = Elton and Gause, ca.1935.)
=20 I believe it was Charlie, sometime around 1859, who wrote: "How strange = it is that a bird, under the form of a woodpecker, should have been created = to prey on insects on the ground; that upland geese, which never or rarely swim, should have been created with webbed feet; that a thrush should = have been created to dive and feed on sub-aquatic insects; and that a petrel should have been created with habits and structure fitting it for the = life of an auk or grebe! and so on in endless other cases. But on the view of each species constantly trying to increase in number, with natural = selection always ready to adapt the slowly varying descendants of each to any unoccupied or ill-occupied place in nature, these facts cease to be = strange, or perhaps might even have been anticipated." =20 =20 David =20 David Hilmy Director of Conservation KuTunza Environmental Education Program Europe: 27 avenue de l'Op=E9ra, 75001 Paris, France USA: 2804 Shepherd St., Mount Rainier, MD 20712; 202-316-4902 =20 =20 =20 -----Original Message----- From: Randy Bangert [mailto:[EMAIL PROTECTED] Sent: Wednesday, November 21, 2007 4:54 PM Subject: Re: Invasives =20 It seems to me that these exotic gallinaceous birds were really =20 introduced to have something different to shoot. Using them to occupy =20 vacant niches appears to just be a convenient excuse foisted on us. =20 After-all, are there really "vacant" niches? One perspective suggests =20 that the niche is defined around the species, so 'vacant' niches do =20 not exist. Another specious triumph for wildlife biology. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D RK Bangert =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 On Nov 21, 2007, at 12:23 PM, Warren W. Aney wrote: =20 > Decades ago there was discussion (and action) regarding the concept of > "unoccupied niches" -- a natural system would have a variety of =20 > niches that > species could occupy and function in. If there was an unoccupied =20 > niche, > than a species could be deliberately brought in to fill that niche to > benefit an entire system. Some examples: ring-necked pheasants and > Hungarian partridge introduced to fill unoccupied niches created by > agricultural development. Chukar partridge brought in to occupy =20 > niches > created by spread of cheatgrass and extirpation of native =20 > gallinules. Wild > turkey brought in to occupy woodland niches presumably unoccupied =20 > or not > fully utilized by native grouse. >=20 > Granted, much of this was done under a rather naive understanding of > ecosystem dynamics. Some might consider wild turkey outside its =20 > historic > range an invasive species, and some such introductions may now seem =20 > unwise > in retrospect. >=20 > This also seems to tie to Kelly's comments about biodiversity -- a =20 > very > diverse ecosystem would have many more niches than a simpler =20 > ecosystem. > This could suggest that a diverse ecosystem might provide =20 > opportunities for > invasive species without penalizing native species. However, I =20 > think we can > find way too many examples of invasives displacing rather than =20 > supplementing > native species. For example, take a look at what I call the dirty =20 > dozen of > Oregon invasives that have taken over or are taking over native-=20 > occupied > niches: >=20 > European starling -- competing with and replacing native passerines > European rock dove ("pigeons") -- replacing native columbids > Herb robert -- replacing native ground covers in otherwise undisturbed > Columbia River Gorge forests > Knotweed (more than one species/subspecies) -- invading and =20 > simplifying > riparian corridors > English ivy -- taking over and simplifying urban and suburban woodland > ground cover > Armenian (Himalayan) blackberry -- extensive monocultures in =20 > riparian areas, > meadows and uplands > Cheatgrass brome -- replacing native bunchgrasses in a variety of =20 > semi-arid > grass and shrubland systems > Bullfrog -- replacing native amphibians > Reed canarygrass -- creating extensive riparian and wetland =20 > monocultures > (may be a native species) > Nutria -- replaced native beaver and muskrat in many habitats > Carp -- replaced native warmwater fishes and degraded their water =20 > habitats > Starthistle (more than one species) -- replacing native rangeland =20 > vegetation >=20 >=20 > The basic questions become: should we (or can we) control and =20 > eliminate the > worst invasives? Or are we condemned to an eternal effort to just =20 > limit and > contain them? Or should we, as some have suggested, just accept the > inevitable and learn to live with them and the resultant degraded > ecosystems? >=20 > Warren W. Aney > Senior Wildlife Ecologist > Tigard, Oregon >=20 > -----Original Message----- > From: Ecological Society of America: grants, jobs, news > [mailto:[EMAIL PROTECTED] Behalf Of James J. Roper > Sent: Tuesday, November 20, 2007 4:32 AM > To: [email protected] > Subject: Re: ECOLOG-L Digest - 15 Nov 2007 to 16 Nov 2007 (#2007-310) >=20 >=20 > Kelly, >=20 > I respectively disagree. Introduced species are bad, no ifs ands or > buts.... Some of them are naturalized and so there is probably =20 > absolutely > nothing we can do about them. The others often have potential for =20 > causing > catastrophe, and it is hubris to think that we can just USE them to =20 > suit OU=3D > R > purposes (of what, fixing something that we already messed up?) =20 > with no > repercussions. >=20 > Also, your argument below is circular. An ecosystem that is very =20 > diverse > has the exotics as part of the calculation of diversity, so less =20 > diverse > will have fewer species overall. Also, healthy does not equal =20 > diverse - > else deserts and alpine systems are all unhealthy. If you say that =20 > within > any biome, the most healthy are the most diverse, I bet you do not =20 > have the > data to support that stand. >=20 > Is leaching copper good? What does "filter" toxics mean? The take =20 > toxins > from the soil and do what with them? And, what do they do in areas =20 > that > have no toxins when they escape cultivation? >=20 > Complicated issues, and I think the best answer is never introduce, =20 > plant > natives, eliminate exotics. >=20 > Cheers, >=20 > Jim >=20 > On Nov 19, 2007 4:54 PM, Kelly Stettner =20 > <[EMAIL PROTECTED]> wrote=3D > : >=20 >> Bill (and all): interestingly, it has been proven that ecosystems =20 >> with a >> large degree of biodiversity (read: "healthy ecosystems") have more >> varieties of invasives present than those ecosystems that have less >> biodiversity. I can dig up the studies, if anyone is interested. >>=20 >> There is always the question of what good do invasive species >> (particularly plants) do in an ecosystem? Yes, here I go again, =20 >> playing >> Devil's Advocate...but consider for a moment how some of these =20 >> rampant, >> densely-populated plant colonies effectively fix carbon from the =20 >> atmosphe=3D > re, >> alter the soil chemistry and hence the soil zoology and biology =20 >> (potentia=3D > lly >> for the better?), and some even filter toxic chemicals from the =20 >> soil. Fo=3D > r >> example, Japanese knotweed (Fallopia japonica, Polygonum =20 >> cuspidatum) appe=3D > ars >> to thrive in old mines, being quite adept at leaching out copper =20 >> from the >> soil. I think that a lot of ecological thought can be turned on =20 >> its ear =3D > by >> thinking outside one's paradigm, looking at the bigger picture. =20 >> But Bill=3D > is >> right in that so very many people make abolishing invasives their =20 >> life's >> work...their sole raison d'etre. Invasive =3D3D Evil, no ifs, ands =20 >> or buts=3D > . >> That is simply not a scientific approach, not is it realistic or =20 >> pragmat=3D > ic. >> Other scenarios and >> paradigms must be recognized and considered in order for =20 >> respectful and >> honest discussion can take place. >>=20 >> Working with knotweed in Vermont, >>=20 >> Kelly Stettner, Director >> Black River Action Team >> Springfield, VT >> www.blackriveractionteam.org >>=20 >>=20 >> --------------------------------------------------------------------- = >> - >>=20 >> Date: Fri, 16 Nov 2007 10:18:47 -0000 >> From: William Silvert >> Subject: Re: ECOSYSTEM Health Alien invasions persistence decline =20 >> limits >> control Re: semi-silly question from John Nielsen >>=20 >> I'll pick up on two of Wayne's points. One is that "some aliens =20 >> that do >> little harm" -- this is true, and some aliens are introduced =20 >> deliberately=3D > . >> Mustangs are alien to N. America, and are widely appreciated. Many >> ornamental plants are deliberately introduced. My mother was a =20 >> member of >> the >> Florida Native Plants Society, and felt that they were fighting a =20 >> losing >> battle against the imports. An interesting downside is that often >> introduced >> plants in dry areas require lots of water and this creates problems. >>=20 >> As for the comment that healthy ecosystems resist invasion, this =20 >> depends >> on >> whether they have had a chance to immunise themselves by past =20 >> experience. >> Because mammals were unknown in Australia, their introduction was >> impossible >> to resist. The same is often true when snakes or mosquitos arrive in >> regions >> where nothing similar has every been present. Often the best defence >> against >> an invading species is a predator that can control it, but if such >> predators >> are not already present, it may take a few million years for them to >> evolve. >>=20 >> Sometimes man has tried to counter one alien invasion by introducing >> another >> alien species to control it -- which brings into action the Law of >> Unintended Consequences. It's a tricky game to play. >>=20 >> Bill Silvert >>=20 >> --------------------------------- >> Be a better sports nut! Let your teams follow you with Yahoo =20 >> Mobile. Try >> it now. >>=20 >=20 >=20 >=20 > --=3D20 > James J. Roper, Ph.D. >=20 > Ecologia e Din=3DE2micas Populacionais > de Vertebrados Terrestres >=20 > Caixa Postal 19034 > 81531-990 Curitiba, Paran=3DE1, Brasil >=20 > E-mail: [EMAIL PROTECTED] > Telefone: 55 41 33857249 > Mobile: 55 41 99870543 >=20 > http://www.bio.ufpr.br/ecologia/ Ecologia e Conserva=3DE7=3DE3o na = UFPR >=20 > http://jjroper.googlespages.com Personal Pages
