[Coral-List] Exotic vs. Invasive
douglasfennertassi at gmail.com
Fri Feb 15 19:13:38 EST 2013
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.
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.
> John F Bruno, PhD
> Department of Biology
> The University of North Carolina at Chapel Hill
> 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
> 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?
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