Why Alien Species Thrive

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!"

Comments

Exploitation, diversity and evolution.

[goombah99]

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.