Re: sidents

From: Scott Chase (
Date: Fri Jul 20 2001 - 18:10:27 BST

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    From: "Scott Chase" <>
    Subject: Re: sidents
    Date: Fri, 20 Jul 2001 13:10:27 -0400
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    >From: Chris Taylor <>
    >Subject: Re: sidents
    >Date: Fri, 20 Jul 2001 16:33:26 +0100
    > > Well if 'system in equilibrium' includes the regime of checks and
    > > that the resident must deal with you may need to rethink the above. What
    > > a native or resident species has homegrown predators and parasites to
    > > with and the invader species comes in on a ship sans parasites from
    > > and enters the resident species' turf sans the invader species normal
    > > of predators? What will hold the invader in check as it competes within
    > > niche that it shares to whatver degree with the resident? What if the
    > > invader carries a parasite or pathogen that it has become immune to over
    > > course of many generations in its homeland and this parasite/pathogen
    > > spread to the resident species or population without immunity or any
    > > of defense? If a resident species has a tenuous grip on its niche and is
    > > just scaping by and an invader has the means to outcompete "hitting the
    > > ground running" with more efficient strategies and an explosive
    > > potential it could wipe out or seriously displace the resident species.
    > >
    > > I do not have much for actual evidence to support the above hypothetical
    > > situations, but the logic alone is possibly damaging to the resident
    > > wins argument.
    >Absolutely - we have to bear in mind here that the principle is just
    >that, and adding factors to the scenario will indeed make it breakdown.
    >If as you say, the invader is unburdened by parasites or specialised
    >predators, because it is an alien species to the ecosystem, it may well
    >displace members of another species from their preferred habitat. Really
    >though this principle applies best within a species, when members of
    >that species are competing for resources.
    OK, I'll have to give that more thought.
    >Also, to put the opposite case
    >for the sake of it, if the invader was not prepared for some aspect of
    >the resident's environment (say some generalist predator that the
    >invader had no experience of) then the ressie would have the jump on the
    Yes, the situation could be reversed and the potential invasive would not
    have a means of displacing the resident. The resident could carry a disease
    organism which it can deal with but the invasive could not or maybe the
    local predators could just as well eat the invasive too.
    >An example of the (entirely valid) scenario you describe might be the
    >demise of the marsupial wolf (Aussie), displaced I think by the dingo.
    >I'm not sure whether Dingos are just better all round (big fast etc.)
    >whether they came to Australasia unburdened by parasites/predators, or
    >were perhaps better at coexisting with humans, but something meant they
    >became the new residents in that niche.
    Speaking of Australia, we in Florida have several invasive plant species
    (eg- australian "pine" and melaleuca) which they can come and take back any
    time they'd like ;-) They also share a problem that we have with "marine
    toads" or "cane toads".

    An example I had in the back of my mind for invasive species possibly
    displacing native species was the two anole species in my area (*Anolis
    carolinensis* and *Anolis sagrei*). The former resident is green yet able to
    change its colors somewhat so people have tended to refer to it with the
    misnomer "chameleon". The latter is the invasive brown anole. I have not
    seen very many green anoles compared to brown anoles lately. I could walk
    out into my front yard right now and see lots of brown anoles scampering

    Using a google search with keywords "Anolis sagrei", "Anolis carolinensis"
    and "invasive" I came up with only a couple pages but it does appear someone
    named Arthur Echternacht is studying the two species in a direction possibly
    pertinent here.

    There were a couple pdf files which are also relevant. Try

    If you do not have Adobe Acrobat reader then google furnishes text versions.

    There is an invasive Cuban treefrog that I have noticed more of lately in
    these parts. I do not know to what degree their niche overlaps with that of
    our native treefrogs, but supposedly the Cuban treefrog can *eat* the native
    treefrogs and just about anything else it encounters.

    How do we fit memes in here...well...possibly how trends of introducing
    non-native species into a region can impact that region. If I'm not mistaken
    Brazilian pepper trees are a shining example and we in Florida are now
    paying the price. The meme shift has recently been towards eradicating these
    nuisance plants when possible.

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