Pardon my math, but that would mean there's far greater diversity, no?

No. If you were making a good faith effort to understand the article, you would realize that the article is referring to the threat to the Galapagos' contribution to the overall biodiversity of the planet. Introducing nonnative species to the Galapagos may lead to the extinction of those species unique to the Galapagos, thereby reducing the overall number of unique species in existence on Earth.

Except that they aren't even unique species and you're begging the question of why these Galapagians should be preserved if they're so maladapted to their environment.

Except that they aren't even unique species

The Galapagos is home to many unique species, i.e., species found nowhere else on Earth.

http://www.cnn.com/EARTH/9803/12/galapagos/

Whether or not they should be preserved is a separate question. That's a question about the worthiness of biodiversity as a goal. If you think it's unworthy, say so and say why.

However, the suggestion you made with your "pardon my math" comment was that introducing a larger number of nonnative species that may drive the smaller number of unique, native ones to extinction somehow increases biodiversity. This suggestion betrays a misunderstandng of the concept of biodiversity.

Are the Galapagos now more or less diverse than they were?

Those aren't unique species, just variants within species.

Where in that WP article does it make clear that none of the threatened species are unique?

You may want to read this. Excerpt:

Endemic species - those found nowhere else on Earth - are common throughout the terrestrial parts of the island group. Approximately 80 percent of all the islands land birds, 97 percent of reptiles and land mammals, and more than 30 percent of plants are endemic

If 30 percent of the plant species are endemic, i.e. unique, that implies that about 150 of those 500 plant species at risk of disappearing are unique. Not to mention the fact that the vast majority of reptile and mammal species are unique, and many of them are threatened by the nonnative ones.

Are the Galapagos now more or less diverse than they were?

No one is claiming that it is a valuable goal to maximize the number of distinct species living in any one particular small region of the world. Nobody wants to make sure zebras and grizzly bears and so on are living on every island in the Pacific. The overall diversity of the globe is the concern- a concern you may or may not share, but you should at least understand what the concern is.

Doesn't say it in the article, but the "species" can interbreed with otthers, so aren't unique species.

So the Galapagos are in fact more diverse, no?

Doesn't say it in the article, but the "species" can interbreed with otthers, so aren't unique species.

Do you have a link that demonstrates this? Wow, how incredibly irresponsible of the Post not to mention that every single one of the threatened species referred to in the article is not a unique species in any meaningful sense, and how incredibly knowledgeable you are to know this about every single one of the species discussed in the article, even though the article doesn't say so. I am very impressed, but would be even more impressed if you have a link that backs your statement up.

So the Galapagos are in fact more diverse, no?

If we were to count up the number of unique species on the Galapagos, write the number down, wipe out all signs of life on the islands, then repopulate the islands with a number of nonnative species larger than the number of the unique species that existed prior to our decimation, then yes, viewed locally I suppose you could say that the Galapagos themselves would then in some sense be more diverse than before. If this is your point, it is frankly not a very interesting point, since maximizing this narrow-mindedly local sense of diversity is no one's goal. As I have already said repeatedly, the overall diversity of the globe is what environmentalists are concerned about.

...the archipelago's isolation from the mainland 600 miles to the east makes it especially vulnerable to new arrivals: "This is a big, big problem. For a long time the animals, the plants, the insects in this area, they didn't have competition."

A discussion on diversity is well and good, but there is another aspect to this which seems more important to me. The Galapagos was the catalyst for Darwin's theory and modern dogma is that new species arise precisely from such isolated breeding groups. How is it then that these, presumably better adapted to this island environment, are unable to compete against other species? Doesn't this call into question the efficacy of the whole "island" paradigm?

Isn't the evolutionary ideal precisely that species unable to compete disappear? Aren't the scientists involved acting in an anti-evolutionary manner and trying to "intelligently design" the islands' ecosystem?

Posted by: jd watson at March 27, 2006 4:18 PM

Jack:

The finches are the most notorious of the putative species that turn out to breed rather easily:

http://ublib.buffalo.edu/libraries/projects/cases/galapagos2.html

As the old saying goes: Only God and Peter Grant can tell the finches apart....

Glad we agree that there is increased diversity.

OJ,

Well done! You have cited a single example of 2 Galapagos-specific species being able to interbreed with each other. If I recall correctly from when I took logic, if a property holds for 2 members (2 particular finch species) of a set (the set of unique Galapagos species) then it must necessarily hold for every member of the set, especially if that set numbers in the hundreds if not thousands.

I'll allow you may have a small legitimate point, i.e., if a pair of unique Galapagos species can actually interbreed, then debatably the total number of unique species on the islands is being overcounted. However, you have provided no estimate of how many distinct species there would be if they were counted in the most conservative way, i.e., taking into account possible interbreedings. But I'm sure every tortoise unique to the Galapagos can interbreed with every unique snail, which can interbreed with every unique hawk, which can interbreed with every unique rodent, so undoubtedly the true number of unique species on the islands is trivially small.

Also, you have provided no evidence that any putatively unique Galapagos species can interbreed with any nonnative species, and you would have to show that this is true for all putatively unique Galapagos species in order possibly to dismiss the environmentalists' concerns. And who knows, maybe you can come up with a single example of this... from which we'll be able immediately to conclude that it holds for all putatively unique Galapagos species, through the airtight logic described above, and therefore we can stop worrying. That'll be great to have my mind put at ease.

Certainly the tortoises will be able to breed with other tortoises, so there are no unique species of tortoise just as finches breed with finches.

First of all, you have not even come close to demonstrating that all Galapagos tortoises can interbreed with each other, nor have you demonstrated that all finches can interbreed with each other. Very unlikely that that's true, in fact.

In any case, if you have a set, set A, of Galapagos tortoises, all of which can interbreed with each other, but none of which can interbreed with anything not native to the Galapagos, then that still counts as a single Galapagos-unique species and an addition to the overall number of species in existence in the world. Now, it's possible that some biologists might count more than one species within set A for other reasons (sometimes the notion of a species is a bit slippery, and that's the kind of situation you pointed out with the finch link) but at the very minimum set A counts as 1 unique species.

Even counting as conservatively as possible there are many such sets like set A and therefore many species found nowhere else but on the Galapagos. Hence, the Galapagos makes a substantial contribution to the overall number of distinct species in existence in the world, and this contribution is threatened by the introduction of nonnative species.

No, they don't. They feature some interesting variations within species.

So far I have provided a link that states that the majority of the bird species, the vast majority of the reptile and mammal species, and about 30% of the plant species found on the Galapagos can be found nowhere else in the world, and you have provided a link showing that a couple of the putatively unique finch species actually can interbreed and therefore should only collectively count as 1 unique species contributed by the Galapagos to the total number of unique species in the world rather than 2.

How do you arrive at the conclusion that there are no unique species contributed by the Galapagos?

Because there's no such thing as species. Take a Galapagos tortoise and you'll be able to breed it with another from Guam. Take a Galapagos finch and you'll be able to breed it with a finch in Maine.

No such thing as species, huh? You really ought to clue in the world's leading biologists on that revelation.

So you're claiming that for every animal native to the Galapagos, there is another animal not native to the Galapagos with which it can interbreed?

I will be absolutely stunned if you can provide credible documentation supporting this claim (note: not documentation of the existence of a single Galapagos species that can interbreed with a non-Galapagos one, documentation of your claim that every Galapagos species can interbreed with a non-Galapagos one.

They know. The best of the lot, Ernst Mayr, was quite frank about their just making it up as they went along:

http://members.aol.com/darwinpage/mayrspecies.htm

Tigers can crossbreed with lions and you think two kinds of finches can't?

The textbook definition of species is a group that can interbreed and produce fertile offspring. I had been presuming you knew this and that our uses of "interbreed" were shorthand for "interbreed and produce fertile offspring", but I was probably presuming too much. Male tigons and ligers are infertile, hence lions and tigers are not the same species. And yes, female ligers and tigons are fertile, but males are infertile, so lions and tigers are 2 different species.

I don't know how you got what you think you got out of that page about Mayr, but Mayr basically crystallized the notion of species with the fertile offspring definition, and only prior to this definition was the notion of species a bit arbitrary. Any reasonable reading of that link you cited does not lead to the conclusion that the notion of species is meaningless. Of course, there are cases where it's a bit hazy whether 2 populations are the same species or not, but the notion is far from meaningless.

I'm not denying there may be a finch here and there that can interbreed with mainland finches; I'm not saying that none of the Galapagos animals can interbreed and produce fertile offspring with non-Galapagos animals. You're in a position where you need to demonstrate that all purportedly Galapagos-unique animals can interbreed and produce fertile offspring with non-Galapagos animals.

If you think this is patently obvious and not in need of demonstration, then I think there's no point in us discussing this further.

No. I'm not. You're in a position where you have to show that each "species" can not breed with any other. They all can as it turns out. In fact some of the offspting of the tiger lion cross are fertile.

What Mayr argued, wrongly, was that species could be differentiated because they chose not to breed with one another. We now know that they will breed or can be bred, so that definition is reduced to an argument for intelligent choice by the creatures, not biology.

They all can, as it turns out

Great, please demonstrate, if you like. Again, a single example does not prove this all-encompassing statement.

I have on my side mainstream, respectable publications referring to numerous unique Galapagos species and the mainstream definition of different species being incapable of fertile offspring. Yes, Mayr also argued for distinctions based on (1) actual failure, as a matter of behavior or geographical distance, to mate and produce fertile offspring in addition to(2) an inability to mate and produce fertile offspring. I take your point that the distinctions based on (1) may have been bogus, but the distinctions based on (2) are quite meaningful. If a goat mounts a dog, they're not going to get an offspring out of it, no matter how hard they try-> 2 different species.

Do you really know for a fact that every single Galapagos species is capable of mating and producing fertile offspring with a non-Galapagos animal?

How do I know that many of them are not capable? Admittedly, it's pretty tough to find an explicit statement on the Web along the lines of "this species of Galapagos tortoise cannot mate and produce fertile offspring with any animal not native to the Galapagos" because that would be a redundant statement, seeing as that is what is meant by species.

If you want to take this as meaning I have failed to demonstrate that the Galapagos has unique species, that's fine- I am happy to leave it here and let the reader judge who is being reasonable.

Yes, I agree that by the time you get as far apart as goats and dogs we may be able to speak seriously about different species. Of course, the canidae are actually a different family than goats, so you've disproved species.