Thanks to BA's list in another thread, it made me think....the point of the srticle is, Are Invasive Species bad? And the article, pretty much says Nope.

BUT....I'd argue that when invasive species crowd out almost all other species (natiev or not) so you are left with a mono-species environment, that that's bad, no matter which side of the debate you look at. Yes, some native species might use the invasive species as food/shelter, but bio-diversity plummets. Not good.

Heck, a human engineered example ist he mono-species cultivation of the forests out here in the Rocky Mountain States......plant all those single-species pine trees, that are all around the same age...and Whoa! favorable conditions come around for the (native) pine beetle and BAM! Good bye forests...

Funny sign, driving down the highway into the Arapahoe National Forest, someone had spray painted FAIL on the sign...I understood when I turnd a corner and as far as I could see.....dead gray trees.....it looked like 99% of the forest was dead.

In addition to the diversity problem, a large function of plants is to convert solar energy into calories in the form on insects who either host or feed on leaves. Since it usually takes thousands of years for the insect/host plant relationship to establish, this is one reason why alien plants can be so successful. Unfortunately it also deprives higher levels of the food chain of the bridge between solar energy and calories. If you are of a certain age you can remember driving at night and ending up with such a buggy windshield you would have to wash it. No more - and everything who lived off those insects in hungrier or dead.

Whoa! Okay, I really shouldn't have written/posted that right before trying to get out of my cube for a meeting. Typos galore! I apologize.

But I agree, invasives are bad because there is no natural balance with the introduced ecosystem regarding bacteria/viruses/insects/herbi­vors that would use the invasive (thinking plants here) as a food souce.....so they can multiply and press onward with little resistance (Like the Nazis martching across France)

But I have to wonder if invasive species taking over is just a form of evolution. The strongest ones survive - others die out? I know that sounds kind of crazy, but with the environment changing so much, it seems logical that the wildlife of the future may be vastly different than the wildlife of the past.

Its not crazy bunny. This has happened many times before humans. For example, lowly mammals exploited the collapse of the dinosaurs. With out this exploitation we wouldn't be here. People talk about ecology like it is static, it only looks that way because our lives are comparatively shor and we don't always look in the right places, but there are always cycles of equilibrium and exploitation by organism that find themselves in more favorable environments either following relocation or by mass extinctions.

yes, but what you are talking about is the natural progression of one dominant species to another.....caused by some sort of 'natural disaster'. (Fire, climate change, meteor strike, etc.) I doubt that mammals would have taken over any ecosystem in the Age of Dinos if something hadn't have happened to cause the demise of the dinos in the first place. mammals just happened to be int he right place at the right time, and were able to take advantage of the opened ecosystems (that they already inhabited).

Evolution is the natural mutation of species.

There is nothing natural about introducing a species into an ecosystem that it hasn't evolved with.

I doubt that if there was a fire that wiped out the forests of the Rockey Mountains, that somehow, a tree from Australia would miraciously appear out of nowhere to repopulate the now denuded slopes.

here is nothing natural about introducing a species into an ecosystem that it hasn't evolved with.

What about the organisms the found their way from asia and austrailia to Hawaii and other Pacific Islands? They all didn't get there at the same time. Many were "invasive species floating in on debris. Introduced species is absolutely natural. Organisms have migrated, or have found themselves isolated in new environments and then exploited those environments long before humans. Evolution is not just about mutations, it is about natural selection and exploiting niches. You see biology as static, but evolution didn't just stop, as we speak it is working on those new introduced species and they will reach an equilibrium at some point. Remember Darwin's finches? They all came from a few ancestral finches that found themselves in a new land (the Galapagos). They were introduced into an ecosystem that hadn't "evolved" with them.

Humans have always been involved with introducing new species to new places. What is the difference whether a snake from Australia finds its way to China via a typhoon or in the hold of a ship? You forget that we are also natural, therefore the things we do and build are also natural, even an ocean liner. By your definition a beaver dam is also "unnatural"

Your argument re Hawaii is disingenous (and the finches) an island springs up in the middle of nowhere, without the eons (and really Hawaii isn't that old in geologic or even biologic time) and conditions necessary, life would probably not evolve independantly. But fortunately the previously barren soils (and volcanic vents) of Hawaii didn't exist in a vacuum....and it was seeded with life from areas where life was already established, then flourished and evolved to fill the previously barren niches of the island(s).

Same with the finches....there were no birds there to begin with. So finches got there, and then evolved to take advantage of the previously underutilized niches. And both the birds and the plants evolved. there were no noative species of finches for the migrated species to overtake.

I do not see biology as static. And introduced species into an already established ecosystem is NOT evolution, (And you're a biologist? Geesh, even this geologist knows what evolution is) it's environmental supplantation.

Ah, the whoel dam argument.....an ocean liner isn't natural....it wouldn't arise out of nothing, while a dam across a river (constructed of trees) could be considered natural, since natural dams are caused all the time by downed trees and floods. So you could say the beaver is just mimiking a nature.

Plus, beaver dams create habitat and species diversity, while all humans (usually) do is cause monolithic species communities with little species diversity.

(and as a bologist, wouldn't you think that diversity is good? Heck, my example of the Rocky Mnt forests is a perfect example why monolithic species communities is bad)

So flotsam from a hurricane carrying organisms to Hawaii is the same as an ocean liner, just as a beaver dam is the same as sticks caused by a flood. You are just unwilling to see human activity as just another natural force.

BTW, species ending up in new environments does effect evolution if you can't see this I can't help you. I am a molecular biologist (immunologist), I do understand evolution. A new species in a new environment acts as a selective pressure on those native organisms around it.

I also reject the notion that we know what is "bad" and "good". Diversity will occur naturally over time. There have been countless examples of times where a species exploits a niche and explodes on to the scene and then dominates for a while until a countermeasure develops. Again, you are thinking staticly, over time an equilibrium will form. A brief lack of diversity is also helpful to evolution of species. For example, mammals existed as shrew-like creatures for a very long time but following the lack of diversity that followed the mass extinction which killed of the dinosaurs mammals were free to fill all sorts of niches from bats to elephants to humans.

Also, your finch argument is kind of weak. So an introduced species doesn't count unless there is already a similar species present?? And Hawaii doesn't count because it is not old enough? You are making up the rules as you go

Ohka:

I also reject the notion that we know what is "bad" and "good".

I'm having a tough time seeing how snakeheads killing off everything else in a pond can be seen as good for anybody but the snakeheads. It's possible something like that would have eventually occurred naturally...but that still doesn't mean it'd be a positive change.

And I'm curious as to where you draw the line on "human activity." If you're talking about unforseen events, like organisms on an ocean liner, I can see where you're coming from. But are you suggesting that it's okay for me to dump my snakeheads into the local pond because they might somehow have ended up there, anyway?

Well, with the snake heads I think it is a matter of perspective. In terms of life in general, no I don't think it is a bad thing to dump snakeheads in the local pond, it may however piss off your neighbors or anyone else that wants to use the pond.

Also, I never said "good for everybody". My point is that there is no good or bad in biology, there just is.