[Coral-List] Exotic vs. Invasive
phoetjes at gmail.com
Mon Feb 18 15:48:22 EST 2013
---------- Forwarded message ----------
From: paul hoetjes <phoetjes at gmail.com>
Date: Mon, Feb 18, 2013 at 2:24 PM
Subject: Re: [Coral-List] Exotic vs. Invasive
To: Douglas Fenner <douglasfennertassi at gmail.com>
Living on Bonaire I feel compelled to come to the defense of the dive
instructor mentioned in the anecdote at the beginning of this
The IUCN defines an alien invasive species as "an alien species which
becomes established in natural or semi-natural ecosystems or habitat,
is an agent of change, and threatens native biological diversity."
"Alien" is synonymized with non-native, non-indigenous, foreign,
exotic, and is taken to mean "a species, subspecies, or lower taxon
occurring outside of its natural range (past or present) and dispersal
potential (i.e. outside the range it occupies naturally or could not
occupy without direct or indirect introduction or care by humans)"
The key distinction for an invasive species then, is that after
introduction by humans it is established outside of its natural range,
and threatens native biological diversity.
A species that has been introduced and has established itself outside
its natural range, but does not threaten native biological diversity
is, therefore, not an invasive species, but merely an established
species, 'established' meaning "successfully producing viable
offspring with the likelihood of continued survival" (CBD). Many
introduced plants that are able to maintain their presence but not to
out-compete native plants fall into this category.
With respect to the Bonaire anecdote: lionfish must be considered
invasive in the Caribbean since they have been shown to threaten
native biodiversity (79% reduction in fish recruitment, Albins and
Tubastrea on the other hand, as far as I know, has not been reported
as having any effects that might indicate any threat to native
biodiversity, and thus cannot be termed an invasive species. In my
book the dive instructor was quite correct, lionfish are invasive,
tubastrea is just an exotic.
As to cute or not cute, rabbits are generally considered cute, but I
don't think there is any doubt that they are an invasive species in
Australia.The "cuteness" of invasive species (remember, many of them
were introduced through the pet trade, i.e., were considered to be
cute enough to buy as a pet) is actually often a problem in the
efforts towards their eradication.
On Fri, Feb 15, 2013 at 8:13 PM, Douglas Fenner
<douglasfennertassi at gmail.com> wrote:
> To me, an introduced species is one that has been moved (intentionally or
> unintentionally) by humans into a new area outside their natural range. In
> my view, an invasive species is an introduced species that goes on to
> invade new areas. Invading new areas often implies effects on the
> ecosystem. There are many marine species that are introduced into harbors
> by shipping. They tend to be species that live in harbors because that is
> where ships are and can pick up species, that is the species' habitat, and
> so often they don't spread outside harbors they are introduced into. But a
> few do, and then I would call them invasive species. I'd argue an
> introduced species that doesn't subsequently expand could sometimes have
> major effects on an ecosystem, if I remember there is a clam in San
> Francisco Bay that came from China and become so abundant that it had
> altered the ecosystem in part of the bay. Invasive species may have larger
> effects simply because they may expand to live in much larger areas, but
> maybe also because they may be strong competitors for native species.
> Level of harm to an ecosystem would probably be hard to quantify.
> Large range expansions can happen naturally, thought they are surely
> much less common than when assisted by people. An example might be the
> cattle egret, which is naturally in Africa, but at one point flew to South
> America, and has subsequently spread throughout much of the Americas.
> The evidence suggests *Tubatraea coccinea* was probably introduced
> into the Caribbean, and probably then spread throughout the Caribbean, Gulf
> of Mexico and to Florida. The evidence is even stronger that Lionfish are
> both introduced and invasive in the Western Atlantic (a number of other
> fish species have also been introduced). There is also genetic evidence
> that the soft coral, *Carijoa*, in the Caribbean came from the Pacific
> relatively recently, and thus is quite likely introduced. It was
> introduced into Hawaii, is invasive and spread widely, and is damaging
> since it grows on back corals and kills them. We talk about "harmful algae
> blooms" so I think we could talk about "harmful invasive species." A
> species that is invasive could in theory be more or less harmful, I suppose.
> Cheers, Doug
> Fenner, D. and Banks, K. 2004. Orange cup coral, *Tubastraea coccinea*,
> invades Florida and the Flower Garden Banks, Northwestern Gulf of Mexico.
> Coral Reefs 23: 505-507.
> Concepcion, G. T., Kahng, S. E., Crepeau, M. W., Franklin, E. C., Coles, S.
> L., Toonen, R. J. 2010. Resolving natural ranges and marine invasions in
> a globally distributed octocoral (genus *Carijoa*). Marine Ecology
> Progress Series 401: 113-127.
> On Sat, Feb 16, 2013 at 6:13 AM, Bruno, John <jbruno at unc.edu> wrote:
> > Hi John
> > Exotic is any introduced species. And there is a gigantic and never
> > ending debate about what to call them, eg, exotic, introduced, alien,
> > non-native, etc
> > The distinction with invasive is somewhat subjective and isn't set in
> > stone, but in general, Invasive exotics are very common, probably to the
> > point of being community dominants and potentially having negative effects
> > on native species. They are also considered to have become "naturalized"
> > ie, established self-sustaining populations, which is a much lower bar than
> > the dominance threshold and Tubastraea would certainly qualify. In fact,
> > in their microhabitat, I think Tubastraea can be quite common and Id be
> > comfortable labeling them as "invasive". And funny, but I just had a
> > manuscript reviewer say lionfish were not invasive, so don't be surprised
> > to hear disagreement about this stuff.
> > Cheers,
> > JB
> > John F Bruno, PhD
> > Professor
> > Department of Biology
> > The University of North Carolina at Chapel Hill
> > www.johnfbruno.com<http://www.johnfbruno.com/>
> > species are exotics that
> > Dear List,
> > Ken Marks recent post concerning Tubastraea micranthus reminded me of an
> > incident that occurred on a recent trip to Bonaire. A divemaster was
> > bemoaning the "invasion" of lionfish. When I mentioned that the "poster
> > coral" for Bonaire (Tubastraea sp) was invasive, I was severely
> > chastised. Lionfish were "invasive", Tubastraea was "exotic".
> > I noted that Ken Marks used both "exotic" and "invasion" in his e-mail.
> > I had never thought about the distinction before.
> > After Googling around a bit, I concluded that if the species under
> > consideration was sort of cute, it was "exotic". If it was ugly, it was
> > "invasive".
> > While that is a vast oversimplification, I wonder if the coral-reef
> > community distinguishes "exotic" from "invasive" and, if so, is there a
> > precise definition of the difference?
> > John
> > _______________________________________________
> > Coral-List mailing list
> > Coral-List at coral.aoml.noaa.gov
> > http://coral.aoml.noaa.gov/mailman/listinfo/coral-list
> PO Box 7390
> Pago Pago, American Samoa 96799 USA
> The views expressed are those of the author alone.
> Coral-List mailing list
> Coral-List at coral.aoml.noaa.gov
More information about the Coral-List