Friday, March 26, 2010

introduced species

We are always hearing about how introduced species have hurt native species, through either predation or competition. On the other hand, what are some examples of introduced species becoming victims of native species? (Hint: there is one such example in the book!). What are some examples of introduced species overall helping the native community? What are some examples of introduced species overall hurting the native community? Looking at these examples, do you think that we should continue to take it upon ourselves to introduce species, or should we be working to make sure that it stops happening? Also, could introduced species eventually be strong evidence for evolution a couple of hundred of years from now, if we start recording if and how they change to their new environments now?


  1. An introduced species, according to, is defined as an alien, exotic, non-indigenous, or non-native species that is living outside its native distributional range as the result of human activity (action of moving species), which could either be deliberate or accidental. With the major technological advancements on the 19th and 20th century, the transplant of species in different geographical areas has been accelerated. Species can be moved by ships, cars, airplanes, etc. and nowadays is a common occurrence. Transplanted species because they are free of predators, parasites, and pathogens may be able to thrive in the new habitats and also can be devastating for an organism that thrives on a species that only inhabits their old environment.

    The fifth chapter of Coyne's novel begins with one of the "marvels of evolution:" the Asian giant hornet, which is the world's largest predatory wasp. This hornet is as long as the human thumb and is colored with orange and black strips. These predators live to serve their young larval grubs and raid the nests of social bees and wasps. Coyne later explains "One of the hornet's prime victims is the introduced European honeybee" (111). In this case, the introduction of European honeybees is beneficial for the voracious predators because they are virtually defense since this species of hornets is native only in Japan.

    "Humans have deliberately introduced many species with good intentions but disastrous effects" (Campbell et al., 2008). In 1890, a citizens' group intentionally brought the European starling into New York's Central Park. They intended to bring all the plants and animals that had been mentioned in Shakespeare's plays. Although the intentions were good, this species increased to a population of 100 million and ended up displacing many native songbirds across North America.

    All in all, whenever there is an example of introduced species being beneficial to its new geographical location there is always another point of view. Although a new habitat may give the species freedom from old environmental stress, it ends up creating new stress for native organisms (predation, disease, etc.). "Introduced species are a worldwide problem, contributing to approximately 40% of the extinctions recorded since 1750" (Campbell et al., 2008). Despite its threat to biodiversity, it could serve as a good evolutionary template because it could be a first hand display of adaptations in a specific environment. Evolution is not easy to spot in the present day (besides bacteria) because of microevolution, so scientists should consider all the dangers and consequences before going through with these procedures and let nature be natural and not artificial.

  2. The previous example of the introduced European honeybee being eaten by the Asian giant hornet is described as an encounter that “involves a merciless mass slaughter that has few parallels in nature.” (Coyne 112) The Asian giant hornet can eat 30,000 honeybees with only a group of 20 to 30, also stated on page 112 of the book. Those numbers are surely staggering, but the fact that the giant hornet is killing off an introduced species makes that startling statistic much less alarming. However, even though that slaughter has “few parallels” in the natural world, undoubtedly some exist. But what could they be? And what kind of ecological horrors could they cause?

    That horror is all too real in the case of the Asian carp, an introduced species that was, “imported from China during the 1970s to clean fish farms of algae in the southern U.S.” (Horng) and migrated north near the great lakes by way of the Mississippi river and other major river channels. So, its source has been determined and reason of introduction (an original benefit) has been established as well, yet the danger has not. The danger behind these carps is that they eat about 1/3 of their body weight per day (which is around 40 pounds) and primarily munch on plankton. Imagine how much plankton, due to their small size, there is in 13.3 pounds! Thousands of these carp are speculated to exist and threaten the Great Lakes ecosystem because of their voracious appetites. Plankton exist close to the very bottom of the lakes’ food chain, which means that a reduction in their numbers subsequently results in major population death of every single species that lives off these plankton existing in the lakes right now. With all of our fresh water coming from lake Michigan, the upset in the ecosystem would undoubtedly affect the quality of water supply as well, which is an extremely unfortunate consequence as these carp set it all in motion.

    So, to answer the question about whether to continue introducing species, the answer would be no! Introduced species are so damaging because they are outsiders to the original ecosystem which is not “set up” to accommodate such invaders, and, as such, they cause massive problems. An ActionBioScience article by Daniel Simberloff states that introduced species “are a major threat to our environment because they can change an entire habitat, placing ecosystems at risk, crowd out or replace native species that are beneficial to a habitat, [and] damage human enterprise, such as fisheries, costing the economy millions of dollars” among other things. Introduced species are very problematic and difficult to control, so all measures should be taken to prevent their introduction into native ecosystems at any cost. The environment is too fragile, a concept oft-revisited in AP Bio, to take such a blow, so we must, continuing the metaphor, stop the punch from being thrown to begin with.

    Page 112 of the book

  3. (Part 1 of 2)

    The above comments provide phenomenal examples of introduced species affecting the ecosystems of various locations. Unfortunately, all too often humans don’t see the connections between our species and the world we live in. They shrug off stories of carp invading the Great Lakes, don’t care about the replacement of native songbirds in Central Park by European starlings, and react to vicious battles between native American alligators and introduced Burmese pythons with awe, not anger. So maybe people will be moved to stop the introduction of nonnative species if they realize that it can directly affect us, too. Luckily there is a historical precedent for that: the European conquest of the Americas, with the help of the trusty smallpox virus.

    Living in the presence of a deadly killer for thousands of years tends to cause a species to adapt and create ways to survive the predator’s lethal attacks. Coyne uses the example of Japanese honeybees to illustrate this point, showing how they vibrate their abdomens in unison within their nest to raise the temperature to 117 degrees Fahrenheit. They do this to kill the Asian giant hornets which are fond of attacking them; they first lure the hornets into their nest and then use their unique temperature-raising behavior to cook the hornets to death (112). This process was a product of natural selection; honeybee colonies that acquired this practice survived and passed the innate behavior on to their offspring, while honeybee colonies that did not acquire this practice were easy pickings for the giant hornets. Similarly, people of the Eastern Hemisphere have been exposed to a plethora of diseases due to their practice of domesticating animals, a practice which began ten thousand years ago. The close proximity with animals allowed diseases to be passed easily from the animals to their human companions, and because humans in the Eastern Hemisphere domesticated a wide variety of animals (cows, sheep, pigs, horses, chickens, etc.) they received a wider variety of diseases. One such disease was smallpox, which first appeared in Egypt over 3000 years ago and ran rampant in periodic epidemics, killing 30% of those who caught the virus and leaving permanent scarring on the faces of the majority of the survivors. However, in the process of killing off so many humans, the virus ensured that many of the survivors would survive because they were naturally resistant to the disease. In addition, those who managed to survive the virus became immune to it afterward. These survivors could then reproduce and pass their resistance to the disease on to their offspring, making it less likely that smallpox would kill them. Because Europeans had shared living space with smallpox for so many years, many of them were either naturally immune thanks to their ancestors or had survived the disease and acquired immunity. Therefore, they could carry the virus to new places (like America) and not be affected.

  4. (Part 2 of 2)

    The introduction of species tends to end badly for either the invaders or the natives because the species have not evolved in conjunction with each other; they haven’t been selected for adaptations that would ensure their survival in the other’s presence. This is what happened to the unfortunate European honeybees that were introduced to Japan. Because they had never encountered the Asian giant hornet in their evolutionary past, they were unprepared to deal with its predatory tactics and fell victim to mass slaughter. Coyne says that “natural selection did not build a defense” for the European honeybee (113). Unlike its Japanese counterpart, the European honeybee has not been selected for the temperature-raising defense mechanism, simply because it has not had to deal with the threat of Asian giant hornets for millions of years. While people may not care about the mass death of honeybees, they probably perk up when they hear of masses of humans being slaughtered, and the Aztec and Inca provide a sad example of this. The Aztec did not have domesticated animals, and the Inca only domesticated the llama and alpaca, which did not carry many diseases. Therefore, there were very few opportunities for those people to contract diseases from animals and proceed to develop immunity or resistance. In addition, viruses such as smallpox depend on a host to carry them to new places, so until the first conquistadors crossed the Atlantic, the natives of America had no exposure to the lethal disease. Like the European honeybee, the Aztec and Inca had not developed a defense through natural selection, and when smallpox was introduced to them by the friendly conquistadors, the eager virus went wild: it reduced the Aztec population from 20 million to 1.6 million in one hundred years, and it killed off 94% of the Inca. Not only did this massive decimation destroy the population, it destroyed the Aztec and Inca cultures and made the discouraged survivors easier for the Spanish to defeat. The Aztec and Inca may have defeated the conquistadors if not for the help of smallpox (and of course the conquistadors took all the credit for this victory for most of the time afterward; not until recently have historians begun to explore the role of smallpox in bringing down the civilizations of pre-Columbian America).

    Now, this all happened five hundred years ago; why should we care about the introduction of nonnative diseases today? The answer is that smallpox is no longer native to Earth. Edward Jenner developed a technique for smallpox inoculation in 1796, and in the time since then the virus has been eradicated from all humans on the planet. Because it is no longer a natural threat, America no longer mandates smallpox inoculation; in fact, it hasn’t done so since 1972. Therefore, if a terrorist group should manage to steal one of the smallpox samples that are still stored in laboratories for scientific purposes and release the virus in America, those born after 1972 (and thus not inoculated against smallpox) would be in serious danger of catching the disease and dying. The natural defenses of the human body against the now-extinct virus have undoubtedly diminished in its absence. But it isn’t only smallpox that we have to worry about. In today’s global society, people can travel virtually anywhere from virtually anywhere, taking with them gratuitous gifts from their homelands. Deadly viruses such as H5N1 and Ebola are not native to America, and as such Americans have not developed resistance against them. If a person from either Southeast Asia or Africa (the respective natural habitats of the above two viruses) were to carry the virus to America, either accidentally or deliberately, it could wreak havoc on an American population that carries no resistance against either virus.

    If that isn’t enough to wake people up to the danger of introduced species, I don’t know what is.

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