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Science

Why Alien Species Thrive 43

Posted by timothy from the perverse-incentives dept.
planux writes "The Sacramento Bee has an interesting article about why invasive animal species thrive, pushing out native species -- sometimes to the point of extinction. Kevin Lafferty, a U.S. Geological Survey marine ecologist at the Western Ecological Research Center in Santa Barbara says "Invasive species end up with about half the parasites, or diseases, they had at home." Animals with an average of 16 parasites on their home turf typically bring about three of the parasites with them to new locations. And only about four new parasites will typically adapt to attack the invading species. Net gain: 9 fewer parasites!"
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Why Alien Species Thrive More

Why Alien Species Thrive

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  • Parasites... (Score:3, Funny)

    by Sunlighter ( 177996 ) on Monday February 10, 2003 @08:41PM (#5275681)

    Makes sense. That's why the colonists came to America. Damned European parasites.

    • HA! If only it were all true - there's actually an interesting point here. When colonists came to America, they brought a whole host of diseases, parasites, etc. with them. They weren't as saturated among the colonies as in Europe, however, leading to some interesting outcomes - e.g. Smallpox. Many colonial Americans were not exposed to it as children in the same manner as Europeans were, making smallpox a highly feared disease that would break out at random amongst the colonies killing many adults. Hell, it almost changed the course of the revolutionary war - for a good review, check out Pox Americana [amazon.com] by Elizabeth Fenn.
    • Is this what allowed the invading alien culture to almost wipe out the indigenous people? The fact that they weren't constrained by such parasites as law enforcement and a sense of ethics?

  • So (Score:2, Insightful)

    by Apreche ( 239272 )
    The logical conclusion is that species that change location more often thrive more often and are therefore "more fit". So when some new weed comes in and starts killing all the grass, let it do so. It's the darwin way.

    • But.. (Score:2, Funny)

      by ApharmdB ( 572578 )
      The problems caused by invasive species are not due to the natural migration or spreading of species. They are caused when humans start shipping stuff all over the world. For example, there was that Chinese lung-fish that some dope in Delaware threw in to a pond roughly a year ago because he didn't want it as a pet anymore.

      If you consider all of this to still be part of Darwinism, then you can look at it from another perspective. People want to protect the environment for their own sakes. For example, they like the varied swamp plants that they have in the Northeast US and hate seeing them all wiped out and replaced with a single invasive plant, a la purple loosestrife.

  • Really simple concept (Score:4, Interesting)

    by Cokelee ( 585232 ) on Monday February 10, 2003 @08:51PM (#5275728)

    A species new to an area has no known predators in that area. Hence, they may thrive and continue to do so until they have wiped out the population of the prey in that area. By that time overpopulation fixes itself because of a shortage in food supply. (or, think long term the development of resistence - if the given species feeds on plants, eventually they will start to taste bad to the species.

    Basically, this is a built-in function of nature. It's just like life. When things are new and great you're happy, but you will adapt to your enviroment and will be bitchin about something soon - I promise.

    It's just like a plant that I've always heard called the "devil's weed." It is a plant that takes over and kills all plant life it touches in the US. It came from China (IIRC), and it exists well in its naturally habitat - there are checks that make sure it doesn't grow like cancer. However, in the US these checks are not in place and it wipes out and strangles every plant it comes in contact with.
    Don't mess with nature, I suppose.

    • Re:Complex concept (Score:5, Insightful)

      by MacAndrew ( 463832 ) on Monday February 10, 2003 @09:35PM (#5275983) Homepage
      Most species are going to have predators pleased to greet them, as most plants and animals are edible. What's important is the edge, a relative rather than absolute advantage over native species.

      A couple of examples are kudzu and zebra mussels -- they don't complain about much. Our local favorite is the Asian "tiger" mosquito. But there are serious bad effects from monoculture -- one disease can destroy everything in its path. Think Windows desktops and a nasty virus.

      Nature will tend to reach an equilibrium, or oscillate wildly, or the newcomers either exterminate the old, or vice versa. There are equatios for estimating equilibrium. Only in a really catastrophic situation does shortage of food supply rein in the invader. But evolution, as opposed to natural selection, is slow, so an alien species can easily exterminate native species before they have a chance to develop defenses, even to the point of suicide. Hawaii is suffering significant losses of species diversity because of newcomers. [hear.org] It takes thousands or millions of years for a new species to develop, yet perhaps the blink of an eye to perish.

      I hate seeing natural selection described as some sort of moral quest for the "best," when it's just a way of explaining natural phenomena (I'm not saying you're doing that, but lots of people do). Darwin didn't judge was was "best," just tried to predict which species would do better under given circumstances. Nature doesn't care about the outcome, or become improved as a result. Species diversity is often the preferable situation.

      Maybe I'm being clueless, but I'm hazy on your relevance to "devil's weed," slang for pot (which does grow quite nicely in the wild).

      • It takes thousands or millions of years for a new species to develop, yet perhaps the blink of an eye to perish.

        Makes you wonder what could happen to humans, with just the right set of environmental/climate changes.
      • I hate seeing natural selection described as some sort of moral quest for the "best," when it's just a way of explaining natural phenomena (I'm not saying you're doing that, but lots of people do).

        I agree.

        Take sickle cell anemia for example. It is a deadly disease, but being heterozygous (that is, having the trait, but only partially or not exhibiting it) for it makes you unsusceptible to malaria. Hence, sickle cell is common in tropical cultures. Is sickle cell a good thing, has it made nature a better place? No, and no, but it has simply continued until evolution produced immunity towards a disease. Was this because cells and our genome have minds. No it's because people that are not heterozygous sickle cell lived, and those that weren't died because of malaria.

        "devils weed"

        Ah yes, that would be kudzu. I apologize in the South that is what I have often heard it called, and I could not remember the real name. On a sidenote, are you saying pot came from China?

        • Re:Complex concept (Score:4, Informative)

          by MacAndrew ( 463832 ) on Monday February 10, 2003 @11:28PM (#5276676) Homepage
          I just checked, and marijuana (from the hemp plant) apparently was cultivated thousands of years ago in central asia (yes, China), then made its way west to Europe. It was imported (alien species!) to the New World very around 1600, as the hemp provided valuable fiber. I saw the stuff growing wild many feet tall in Asia, which was kind of startling. The varieties grown for drug use has been refined to have many times the THC of the wild variety. The US prohibits growing low-THC hemp for the idiotic reason that it makes law enforcement look bad. Soem argue it does have economic value.

          Don't ask me to connect pot and natural selection....

          Sickle cell is oh-so-nasty, and even the heterozygotes show some mild symptoms. Yes, I learned the same thing sickle cell and malaria [nih.gov]. Only a fraction (8-45% by region) of Africans have the trait, so probably people with it simply survive somewhat more often. I guess it was a glitch at some point that helped, but was not do-or-die essential to survival.

          • Re:Complex concept (Score:3, Interesting)

            by Alsee ( 515537 )
            Only a fraction (8-45% by region) of Africans have the trait, so probably people with it simply survive somewhat more often.

            The key to understanding the genetics of sickle cell is to realize that the benefit is in having one normal gene and one sickle gene. In that case you get most of the protection against malaria and little of the harm of sickle cell.

            Anyone with 2 sickle cell genes tends to dies of sickle cell anemia and anyone with no sickle genes tends to die of malaria. Most survivors will have one of each gene. The problem is that a population entirely of people with one of each gene is not "stable". When they reproduce their children will be 25% double sickle cell anemic, 25% sickle-cell-free and malaria vulnerable, and 50% healthy and protected.

            The greater the malaria threat the closer the population will get to 50% sickle cell genes. As the threat diminishes the percentage will shift towards zero.

            -
      • Darwin didn't judge was was "best," just tried to predict which species would do better under given circumstances. Nature doesn't care about the outcome, or become improved as a result. Species diversity is often the preferable situation.

        No, you're wrong. Modern evolutionary theory avoids talking about 'best'; Darwin certainly had no such compunctions. Here's a quote from On The Origin of Species:


        To my mind it accords better with what we know of the laws impressed on matter by the Creator, that the production and extinction of the past and present inhabitants of the world should have been due to secondary causes, like those determining the birth and death of the individual...And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress toward perfection.


        Now, in the context of 'perfecting' mental endowments, read the following excerpt from The Descent of Man:


        The belief that there exists in man some close relation between the size of the brain and the development of the intellectual faculties is supported by the comparison of the skulls of savage and civilized races, of ancient and modern people, and by the analogy of the whole vertebrate series.... Dr. J. Bernard Davis has proved by many careful measurements that the mean internal cpacity of the skull in Europeans is 92.3 cubic inches; in Americans, 87.5; in Asiatics, 87.1; and in Australians, only 81.9 cubic inches.


        Darwin was a good scientist, but he never entirely shook off the prejudices of his day.
        • You're right, and I do recall Darwin's racist streak. However, I also remember it as something engrafted on the basic theory, and relatively isolated.

    • Not so simple concept (Score:2, Interesting)

      by jearbear ( 10099 )
      At the same time, said new individual may be emerging into an environment it is totally unprepared for. Think of a plant going into an environment with lots of herbivores. While all of the native plants may have evolved nasty chemicals and physical defenses which have co-evolved with the local herbivores, the non-native plant has bupkis, and gets hammered as soon as it establishes itself.

      Of course, there are a huge number of other wrinkles to this - higher dispersive ability and more efficient resource usage due to a the new plant not devoting any energy to costly defenses, etc., but this hypothesis was by no means a sure thing - that it has borne out is really quite extraordinary, and may yield some interesting insite into top-down versus bottom-up control of species invasions.

    • Yes, I knew it had to do something with monopoly and all that.

  • Any info on why they adapt so well to the new cuisine?
    • Well, common sense would dictate that in order for an organism to survive and reproduce in the first place, and hence invade, it has to be able to get its food from somewhere - there's an immense literature out there about attempts by man to introduce a variety of organisms for aquaculture, farming, etc, and failing due to those organisms not being able to eat, reproduce, or what have you. It follows then that if we see a succesful non-native organisms, its pappy was able to eat something when he first landed, and so can it!

  • Ripley: How do we kill it? Ash: You can't. Parker: Bullshit! Ash: You still don't know what you're dealing with do you? Perfect organism. Its structural perfection is matched only by its hostility. Lambert: You admire it. Ash: I admire its purity, its sense of survival; unclouded by conscience, remorse, or delusions of morality. Parker: I've heard enough and I'm asking you to pull the plug. Ash: One more word. I can't speak for your chances, but... you have my sympathies.

  • Exploitation, diversity and evolution. (Score:5, Interesting)

    by goombah99 ( 560566 ) on Monday February 10, 2003 @09:29PM (#5275917)
    this reminded me of an older paper that tried to rationalize why optimal growing conditions does not seem to favor rapid evolution of a species. That is what scant evidence there is, it appears that evolutionary diversity and advancement occurs under not the optimal growing conditions but rather in the harshest. e.g. at the highest altitude, hottest temperaures or any place life struggles to survive.

    While its obvious that harsh conditions by themselves impose evolutionary pressure this does NOT promote diversity--after all that pressure only is placed on genes that govern adaptation to the environment, and even there there is generally a narrowing of the gene pool not an expansion.

    No instead the diversity arises because you have left your old balanced environment and predators, and thus have LOST the finely honed evolutionary pressure on those genes. thus you can evolve semi randomly with little selective pressure, leading to diversity. Another factor leading not to diversity but to rapid differentiation is that when these new traits that have nothing to do with survival get chromosomally linked to the features that enhance a species survival in the harsh environment, they get amplified.

    some people call this the poker hand effect. You dont need a royal straight flush to win. all you have to do is beat your opponents. Or to put it another way if you are trying to live in a chemical wasteplant out flow, you dont have to generate a a very good enzyme for digesting plastics, anything that is better than your competitors is good enough for now. You can evolve it more later.

    this explanation is perhaps the simplest and best answer to creationists who want to insist that life is too complex a process to spring into existance fully developed (.e.g. behe's mouse trap argument). The answer is that being adaptive can beat being the best.

    anyhow its interesting that a species poised to exploit an opportunity will evolve faster than one that dominates its native environment.
    • Or to put it another way, people with a family history of being prone to genetic mutation, or behavioural disorders, may in the long long long term have a greater influence on the genetics and sociology of future humanity, than those beautiful, well behaved people. What I cant decide is if this slash dot community represents a breeding place for diversification under harsh conditions or is a swarm fuzzy well balanced world for a particularly obnoxious phenotype and is thus not promoting its own evolution.
    • this explanation is perhaps the simplest and best answer to creationists who want to insist that life is too complex a process to spring into existance fully developed (.e.g. behe's mouse trap argument). The answer is that being adaptive can beat being the best.

      But being adaptive is a part of the most basic life functions we observe. The creationist statement that life is too complex to spring into existance fully developed is targetted primarily at abiogenesis research. All our current knowledge does not have an accepted natural mechanism by which DNA or even RNA could come into being. They are the simplest known mechanism that provide the adaptive ability of life. Thus there still isn't any known adaptive mechanism to get to DNA/RNA. Creationists disagree with the assumption that such a mechanism exists. And our current evidence really doesn't strongly(I said strongly, so no troll/flamebait rating please) support the assumption of a naturalistic mechanism existing. I don't think this observation of adaptivity will win many arguments with creationists.
      • in my own defense this is not a thread about creationism, its about adaption. So I spent very few words on it. I was just trying to make an observation about a link between the two, not a full argument. Creationist tend to look at evolution statically and want to say see this critter is optimal but theres no way it could have reached this perfect state incrementally. I wanted to remark, that evolution is a dynamics process and its not about being optimal, its about who survives, and adatation is one survivial strategy.

        but since you brought it up let me address one small point in your comment.

        Thus there still isn't any known adaptive mechanism to get to DNA/RNA.

        While of course we cant say "whence dna" there are a lot of good leads at the moment. The most promising in my opinion is the growing realization is that RNA can do both the functions of DNA and Proteins. That is it is an information storage system that can replicate itself and edit itself, and it can form chemically active self-folded structures just like proteins. In fact in a perfectly benign environment its not absurd to suggest that life could be composed entirely out of RNA and small naturally available molecules.

        The reason life could not currently be composed out of RNA is that its a hostile world and a lot of the precursur molecules dont exist anymore (other animals used them up). RNA is chemically unstable and easily digested. plus its reaction rates are too slow making it a lousy catylist for many activities. On the other hand in a primordial world, without hostile agents, and no competiton one has all the time in the world to wait for a slow catylist. Its the poker hand again: a pair of twos wins if everyone has has dick. thus its not unthinkable that RNA is the missing link. the fact that RNS still is the middle man speaks volumes. But we will probably never really know unless we find some alternate biospace that evolved differently (the possible discovery of nanobes in deep mines and maybe asteroids comes to mind).

        Now the sentence in my discourse you keyed on ("The answer is that being adaptive can beat being the best." ) could obviously be made into a book length discussion. I probably could have chosen my words more carefully too. perhaps I should have said "being adaptive can beat being the most optimally adapted organism to a current environment". For example, if every one lives on mice then the one with the perfect irreducibly complex mouse trap may be the dominant species, but a crappy one that also floats or catches fish on out of every thousand tries might be a more adaptive but marginal species in the present environment (e.g. imagine a speer planted in the ground that requires the mouse or fish to fall on it. Not exactly irreducibly complex, but definitely adaptive. one does not need the perfect mouse trap to get started if a shift (e.g. waterworld) in environment suddenly gives you an advantage.). There are others who have actually taken behe mouse trap argument literally and shown one can infact reduce it.

        but I'm getting off point here.

      • Creationist don't seem to be too adaptive.

  • I have seen this happen first hand. (Score:5, Funny)

    by Neck_of_the_Woods ( 305788 ) on Monday February 10, 2003 @09:34PM (#5275969) Journal

    On my native network where the domiant boxen is Windows, I have found that non-indiginous boxen such as Solaris, Linux, and Mac are slowly taking over one part of my network. They often don't fall victum to the numerous virus and dipshit users. Either by design or just from complexity built into thier mutated form. I have also noticed a cross pollonation that has caused a raise in stability in our fringe windows boxes that are protected by the Alien unix and linux boxen.

    It is all just nature at work, I one day hope to see all my boxeb being some kind of freakish hybrid of windows and unix/linux....or maybe the dominate boxen will take over the whole network.

  • J'Original (Score:4, Informative)

    by jearbear ( 10099 ) on Monday February 10, 2003 @09:55PM (#5276139) Homepage
    If you're somewhere that has access to Nature [nature.com]'s archives, you can read the two original articles this one was based off of:

    Release of invasive plants from fungal and viral pathogens [nature.com] and [nature.com]
    Introduced species and their missing parasites

  • Great argument for space colonization (Score:4, Interesting)

    by Mick D. ( 89018 ) on Monday February 10, 2003 @10:14PM (#5276230) Homepage Journal
    I am only half joking when I say that. With all the debate nowadays about the value of manned space flight, this is actually a very good argument for putting people out there. Space is harsh and there are many perils that we have to learn to deal with out there. But, those are the equivalent to the new parasites in any new environment.

    For a little idea of how many paraites we would bring with us just look at the Earth similar ailments that astronauts get. They rarely get sick and never get into car accidents.

    It just goes to show that getting into space and staying there might not be as daangerous for the log stay as just visiting is.

  • Good book that deals with complex systems etc. (Score:3, Interesting)

    by muonzoo ( 106581 ) on Monday February 10, 2003 @10:33PM (#5276338)
    There is a really good book that addressing this, along with lots of other geek interesting things. I read it a few years ago, but it is equally interesting today as it was then.

    If you have a favorite book search engine, then you might only want the details:
    ISBN number: 0679425632
    Title: Why things bite back: Technology and the Revenge of Unintended Consequences
    Author: Edward Tenner
    Publisher: Random House Canada [randomhouse.ca]
    Published: May 1996

    If you want, you can see it at Amazon [amazon.com], Barnes and Noble [barnesandnoble.com] and Indigo [indigo.ca].
    Go read it. It's interesting.

  • OK, this is a stupid question, but... (Score:3, Interesting)

    by Unknown Poltroon ( 31628 ) <unknown_poltroon1sp@myahoo.com> on Monday February 10, 2003 @11:18PM (#5276605)
    Whynot transplant the speices thats being wiped out back to the invaders home territory? Would the opposite apply? Cane toads are wiping out the austrailian frogs, would transplanting the austraialn frogs to the cane toads native habitat work the same way? I konw it would be bad enviornmentally, but it would be a fun experiment.
    • I konw it would be bad enviornmentally, but it would be a fun experiment.

      Chuckle. I can think of quite a few "fun experiments" that would be rather bad enviornmentally :)

      I bet with a hundred or so nukes we could break up the entire antarctic iceshelf. You could probably throw up temporary ski resorts on the several-hundred-mile long icebergs when they drift up to the equator. Cooool!

      -
  • Rats, cockroaches, and humans. (Some of, not sure if list is exclusive) the only species that exist on all 7 continents. If and when humans spread out far enough to interact with extraterrestrial species, chances are they'll not only have to cope with us, but those other two as well.
  • Only a few famous cases get the attention for surviving in alien environments.

    An extreme example would be why don't we have dolphins here in Oklahoma? Afterall, we are surrounded on all sides by their natural environment, why haven't they invaded? They've even been actively transported into the area by humans. Why haven't they taken over? The answer is simple, they just can't live in/on the dirt. They gotta have seawater and there's just not very much available in OK.

    Like I said, most don't. If you doubt the "most", just look around and count the number of species living in any particular ecosystem, then count the number of species living elsewhere and compare the numbers.

  • Do they need any insecteside?

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