[APWG] Invaders Article

Sat Sep 13 00:04:49 CDT 2008

>
> Hey Everyone,
>
>    While I agree with Mike that this article highlights the threat of
> species invasions, I would like to offer another important conclusion.  In
> the original Proceedings of the National Academy of Sciences article by Dr.
> Sax & Dr. Gaines, the authors discuss not only the impact of exotic plants,
> but also of exotic birds.  In the case of plants (as pointed out in the
> NYTimes) we see that there is a continual addition of new species, whereas
> with birds, we see that additions of new species often result in extinction
> events of pre-existing birds.  While I will not argue that species
> invasions aren't as threatening for plants as they are for birds (because we
> all know they are), I think that the most important thing is that we are
> beginning to realize that certain types of communities aren't saturated with
> species.  Forever we have thought that communities and ecosystems are
> tightly co-evolved and are the result of succession of species that are
> optimally adapted for certain environments.  In the case of plants, I
> think that we now see that this isn't always the case.  As always, I think
> that we will see problems down the line resulting from these invasions (e.g.
> extinction time-lags), but maybe there is more hope than we thought for
> native taxa to not always be forced out.
>
> Feel free to bash this commentary as you see fit,
>
> Matt Heard
>
> On Thu, Sep 11, 2008 at 11:49 AM, Michael Schenk <schenkmj at earthlink.net>wrote:
>
>> Bob, thanks for the article.
>>
>> This article contains an excellent summary of the unprecedented threat of
>> the modern spread of invasive species: the vastly accelerated rate of
>> invasion, coupled with the stress placed on ecosystems by induced rapid
>> changes. Read through to the latter part, past the feel-good stuff about the
>> fossil record. Of course the fossil record doesn't contain anything
>> comparable. There was no highly mobile technological species imposing
>> geological rates of change in decades as opposed to millions of years.
>>
>> Change in species diversity and ranges happens constantly. It's the rate
>> of change which is worrisome. The rate of change from a major asteroid
>> strike, scaled in weeks or years, is more similar to the current rate of
>> change than the megayears we'll find in the fossil record.
>>
>> Mike
>>
>>
>> >Message: 1
>> >Date: Wed, 10 Sep 2008 14:53:13 -0400
>> >From: Bob Beyfuss <rlb14 at cornell.edu>
>> >Subject: [APWG] Fwd: Friendly Invaders
>> >To: apwg at lists.plantconservation.org
>> >Message-ID:
>> >       <6.2.1.2.2.20080910145256.051d6008 at postoffice8.mail.cornell.edu>
>> >Content-Type: text/plain; charset="iso-8859-1"
>> >
>> >
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>> >>To: rlb14 at cornell.edu, <jrh45 at cornell.edu>
>> >>From: Gary Goff <grg3 at cornell.edu>
>> >>Subject: Fwd: Friendly Invaders
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>> >>>To: CCE-INVASIVESPECIES-L at cornell.edu
>> >>>From: "Robert J. Kent" <rjk13 at cornell.edu>
>> >>>Subject: Friendly Invaders
>> >>>Cc: Charlie Scheer <cfscheer at optonline.net>
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>> >>>X-LYRIS-Message-Id:
>> >>><LYRIS-7370812-3026195-2008.09.09-08.57.30--grg3#cornell.edu@
>> list.cornell.edu>
>> >>>
>> >>>NY Times
>> >>>September 9, 2008
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>Friendly Invaders
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>By <http://query.nytimes.com/search/query?ppds=bylL&v1=CARL
>> >>>ZIMMER&fdq=19960101&td=sysdate&sort=newest&ac=CARL
>> >>>ZIMMER&inline=nyt-per>CARL ZIMMER
>> >>>
>> >>>New Zealand is home to 2,065 native plants found nowhere else on Earth.
>> >>>They range from magnificent towering kauri trees to tiny flowers that
>> >>>form tightly packed mounds called vegetable sheep.
>> >>>
>> >>>When Europeans began arriving in New Zealand, they brought with them
>> >>>alien plants ? crops, garden plants and stowaway weeds. Today, 22,000
>> >>>non-native plants grow in New Zealand. Most of them can survive only
>> with
>> >>>the loving care of gardeners and farmers. But 2,069 have become
>> >>>naturalized: they have spread out across the islands on their own.
>> There
>> >>>are more naturalized invasive plant species in New Zealand than native
>> species.
>> >>>
>> >>>It sounds like the makings of an ecological disaster: an epidemic of
>> >>>invasive species that wipes out the delicate native species in its
>> path.
>> >>>But in a paper published in August in The
>> >>><
>> http://topics.nytimes.com/top/reference/timestopics/organizations/p/proceedings_of_the_national_academy_of_sciences/index.html?inline=nyt-org
>> >Proceedings
>> >>>of the National Academy of Sciences, Dov Sax, an ecologist at
>> >>><
>> http://topics.nytimes.com/top/reference/timestopics/organizations/b/brown_university/index.html?inline=nyt-org
>> >Brown
>> >>>University, and Steven D. Gaines, a marine biologist at the University
>> of
>> >>>California, Santa Barbara, point out that the invasion has not led to a
>> >>>mass extinction of native plants. The number of documented extinctions
>> of
>> >>>native New Zealand plant species is a grand total of three.
>> >>>
>> >>>Exotic species receive lots of attention and create lots of worry. Some
>> >>>scientists consider biological invasions among the top two or three
>> >>>forces driving species into extinction. But Dr. Sax, Dr. Gaines and
>> >>>several other researchers argue that attitudes about exotic species are
>> >>>too simplistic. While some invasions are indeed devastating, they often
>> >>>do not set off extinctions. They can even spur the evolution of new
>> diversity.
>> >>>
>> >>>?I hate the ?exotics are evil? bit, because it?s so unscientific,? Dr.
>> >>>Sax said.
>> >>>
>> >>>Dr. Sax and his colleagues are at odds with many other experts on
>> >>>invasive species. Their critics argue that the speed with which species
>> >>>are being moved around the planet, combined with other kinds of stress
>> on
>> >>>the environment, is having a major impact.
>> >>>
>> >>>There is little doubt that some invasive species have driven native
>> >>>species extinct. But Dr. Sax argues that they are far more likely to be
>> >>>predators than competitors.
>> >>>
>> >>>In their new paper, Dr. Sax and Dr. Gaines analyze all of the
>> documented
>> >>>extinctions of vertebrates that have been linked to invasive species.
>> >>>Four-fifths of those extinctions were because of introduced predators
>> >>>like foxes, cats and rats. The Nile perch was introduced into Lake
>> >>>Victoria in 1954 for food. It then began wiping out native fish by
>> eating them.
>> >>>
>> >>>?If you can eat something, you can eat it everywhere it lives,? Dr. Sax
>> >>>said.
>> >>>
>> >>>But Dr. Sax and Dr. Gaines argue that competition from exotic species
>> >>>shows little sign of causing extinctions. This finding is at odds with
>> >>>traditional concepts of ecology, Dr. Sax said. Ecosystems have often
>> been
>> >>>seen as having a certain number of niches that species can occupy. Once
>> >>>an ecosystem?s niches are full, new species can take them over only if
>> >>>old species become extinct.
>> >>>
>> >>>But as real ecosystems take on exotic species, they do not show any
>> sign
>> >>>of being saturated, Dr. Sax said. In their paper, Dr. Sax and Dr.
>> Gaines
>> >>>analyze the rise of exotic species on six islands and island chains.
>> >>>Invasive plants have become naturalized at a steady pace over the last
>> >>>two centuries, with no sign of slowing down. In fact, the total
>> diversity
>> >>>of these islands has doubled.
>> >>>
>> >>>Fish also show this pattern, said James Brown of the
>> >>><
>> http://topics.nytimes.com/top/reference/timestopics/organizations/u/university_of_new_mexico/index.html?inline=nyt-org
>> >University
>> >>>of New Mexico. He said that whenever he visits a river where exotic
>> fish
>> >>>have been introduced, ?I ask, ?Have you seen any extinctions of the
>> >>>natives?? ? ?The first response you get is, ?Not yet,? as if the
>> >>>extinction of the natives is an inevitable consequence. There?s this
>> >>>article of faith that the net effect is negative.?
>> >>>
>> >>>Dr. Brown does not think that faith is warranted. In Hawaii, for
>> example,
>> >>>40 new species of freshwater fish have become established, and the 5
>> >>>native species are still present. Dr. Brown and his colleagues
>> >>>acknowledge that invasive species can push native species out of much
>> of
>> >>>their original habitat. But they argue that native species are not
>> >>>becoming extinct, because they compete better than the invasive species
>> >>>in certain refuges.
>> >>>
>> >>>These scientists also point out that exotics can actually spur the
>> >>>evolution of new diversity. A North American plant called saltmarsh
>> >>>cordgrass was introduced into England in the 19th century, where it
>> >>>interbred with the native small cordgrass. Their hybrid offspring could
>> >>>not reproduce with either original species, producing a new species
>> >>>called common cordgrass.
>> >>>
>> >>>Long before humans moved plants around, many plants hybridized into new
>> >>>species by this process. ?Something like a third of the plant species
>> you
>> >>>see around you formed that way,? Dr. Sax said.
>> >>>
>> >>>Biological invasions also set off bursts of natural selection. House
>> >>>sparrows, for example, have moved to North America from Europe and have
>> >>>spread across the whole continent. ?Natural selection will start to
>> >>>change them,? Dr. Sax said. ?If you give that process enough time, they
>> >>>will become new species.?
>> >>>
>> >>>?The natives themselves are also likely to adapt,? Dr. Sax added. Some
>> of
>> >>>the fastest rates of evolution ever documented have taken place in
>> native
>> >>>species adapting to exotics. Some populations of soapberry bugs in
>> >>>Florida, for example, have shifted from feeding on a native plant, the
>> >>>balloon vine, to the goldenrain tree, introduced from Asia by
>> landscapers
>> >>>in the 1950s. In five decades, the smaller goldenrain seeds have driven
>> >>>the evolution of smaller mouthparts in the bugs, along with a host of
>> >>>other changes.
>> >>>
>> >>>In Australia, the introduction of cane toads in the 1930s has also
>> >>>spurred evolution in native animals. ?Now that you have cane toads in
>> >>>Australia, there?s a strong advantage for snakes that can eat them,?
>> said
>> >>>Mark Vellend, of the University of British Columbia. Cane toads are
>> >>>protected by powerful toxins in their skin that can kill predators that
>> >>>try to eat them. But in parts of the country where the toads now live,
>> >>>black snakes are resistant to the toxins in their skin. In the parts
>> >>>where the toad has yet to reach, the snakes are still vulnerable.
>> >>>
>> >>>Dr. Brown argues that huge negative effects of invasions are not
>> >>>documented in the fossil record, either. ?You see over and over and
>> over
>> >>>again that this is never the case,? he said. Species have invaded new
>> >>>habitats when passageways between oceans have opened up or when
>> >>>continents have collided.
>> >>>
>> >>>?The overall pattern almost always is that there?s some net increase in
>> >>>diversity,? Dr. Brown said. ?That seems to be because these communities
>> >>>of species don?t completely fill all the niches. The exotics can fit in
>> there.?
>> >>>
>> >>>In a recent paper in the journal Science, Peter Roopnarine of the
>> >>>California Academy of Sciences and Geerat Vermeij of the University of
>> >>>California, Davis, looked at the history of invasions among species of
>> >>>mollusks, a group that includes mussels, clams and whelks. About 3.5
>> >>>million years ago, the mollusks of the North Pacific staged a major
>> >>>invasion of the North Atlantic. Before then, the Arctic Ocean had
>> created
>> >>>a barrier, because the mussels could not survive in the dark,
>> >>>nutrient-poor water under the ice.
>> >>>
>> >>>A period of
>> >>><
>> http://topics.nytimes.com/top/news/science/topics/globalwarming/index.html?inline=nyt-classifier
>> >global
>> >>>warming made the Arctic less forbidding. Yet the migration did not lead
>> >>>to a significant drop in the diversity of the Atlantic native mussels.
>> >>>Instead, the Atlantic?s diversity rose. Along with the extra exotic
>> >>>species, new species may have arisen through hybridization.
>> >>>
>> >>>The Arctic Ocean is now warming again, this time because of human
>> >>>activity. Computer projections indicate it will become ice-free at
>> least
>> >>>part of the year by 2050. Dr. Roopnarine and Dr. Vermeij predicted that
>> >>>today?s mollusks would make the same transoceanic journey they did 3.5
>> >>>million years ago. They also expect the invasion to increase, rather
>> than
>> >>>decrease, diversity.
>> >>>
>> >>>But critics, including Anthony Ricciardi of
>> >>><
>> http://topics.nytimes.com/top/reference/timestopics/organizations/m/mcgill_university/index.html?inline=nyt-org
>> >McGill
>> >>>University in Montreal, argue that today?s biological invasions are
>> >>>fundamentally different from those of the past.
>> >>>
>> >>>?What?s happening now is a major form of global change,? Dr. Ricciardi
>> >>>said. ?Invasions and extinctions have always been around, but under
>> human
>> >>>influence species are being transported faster than ever before and to
>> >>>remote areas they could never reach. You couldn?t get 35 European
>> mammals
>> >>>in New Zealand by natural mechanisms. They couldn?t jump from one end
>> of
>> >>>the world to another by themselves.?
>> >>>
>> >>>It is estimated that humans move 7,000 species a day. In the process,
>> >>>species are being thrown together in combinations that have never been
>> >>>seen before. ?We?re seeing the assembly of new food webs,? said Phil
>> >>>Cassey of the University of Birmingham in England. Those new
>> combinations
>> >>>may allow biological invasions to drive species extinct in unexpected
>> ways.
>> >>>
>> >>><
>> http://health.nytimes.com/health/guides/disease/botulism/overview.html?inline=nyt-classifier
>> >Botulism,
>> >>>for example, is killing tens of thousands of birds around the Great
>> >>>Lakes. Studies indicate that two invasive species triggered the
>> outbreak.
>> >>>The quagga mussel, introduced from Ukraine, filters the water for food,
>> >>>making it clearer. The sunlight that penetrates the lakes allows algae
>> to
>> >>>bloom, and dead algae trigger an explosion of oxygen-consuming
>> bacteria.
>> >>>As the oxygen level drops, the botulism-causing bacteria can multiply.
>> >>>The quagga mussels take up the bacteria, and they in turn are eaten by
>> >>>another invasive species: a fish known as the round goby. When birds
>> eat
>> >>>round gobies, they become infected and die.
>> >>>
>> >>>?If you pour on more species, you don?t just increase the probability
>> >>>that one is going to arrive that?s going to have a high impact,? Dr.
>> >>>Ricciardi said. ?You also get the possibility of some species that
>> >>>triggers a change in the rules of existence.?
>> >>>
>> >>>Dr. Ricciardi argues that biological invasions are different today for
>> >>>another reason: they are occurring as humans are putting other kinds of
>> >>>stress on ecosystems. ?Invasions will interact with climate change and
>> >>>habitat loss,? he said. ?. We?re going to see some unanticipated
>> synergies.?
>> >>>
>> >>>Both sides agree, however, that decisions about invasive species should
>> >>>be based on more than just a tally of positive and negative effects on
>> >>>diversity. Invasive weeds can make it harder to raise crops and graze
>> >>>livestock, for example. The Asian long-horned beetle is infesting
>> forests
>> >>>across the United States and is expected to harm millions of acres of
>> >>>hardwood trees. Zebra mussels have clogged water supply systems in the
>> >>>Midwestern United States. Exotic species can also harm humans? health.
>> >>>?<
>> http://health.nytimes.com/health/guides/disease/west-nile-virus/overview.html?inline=nyt-classifier
>> >
>> >>>West Nile virus,
>> >>><
>> http://health.nytimes.com/health/guides/disease/the-flu/overview.html?inline=nyt-classifier
>> >influenza
>> >>>? these things are invasions,? Dr. Ricciardi said.
>> >>>
>> >>>On the other hand, some invasive species are quite important. In the
>> >>>United States, many crops are pollinated by honeybees originally
>> >>>introduced from Europe.
>> >>>
>> >>>?It?s not that this is all good or all bad, and I?m not sure science
>> >>>should be the arbiter,? Dr. Brown said. ?Placing values on these things
>> >>>is the job of society as a whole.?
>> >>
>>
>> >>-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-
>> >>
>> >>Gary R. Goff
>> >>104 Fernow Hall, Cornell University, Ithaca, NY 14853.
>> >>ph. 607/255-2824;  fax 607/255-2815;  e-mail: grg3 at cornell.edu
>> >>www.cornellmfo.info
>> >>http://www.dnr.cornell.edu/people/ra/profiles/goff.html
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>
>
> --
> ********************************************************
> Matt Heard
> PhD Student
> Brown University
> Ecology and Evolutionary Biology
> 80 Waterman St. Box G-W
> Providence, RI 02912
> heard.m at gmail.com
> heard.m.googlepages.com
>


-- 
********************************************************
Matt Heard
PhD Student
Brown University
Ecology and Evolutionary Biology
80 Waterman St. Box G-W
Providence, RI 02912
heard.m at gmail.com
heard.m.googlepages.com
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