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Jeroen Speybroeck wrote:The origin of the species on Sicily may relate to an ancient introduction.
http://www.telegraph.co.uk/news/worldne ... f-war.html
At first, this seemed far-fetched, but if the species is really restricted to the area where it was now
found, an introduction seems likely? Genetics will have to tell us if the Greek snake throwers collected
there snakes at home or in northern Africa .

(1) What does the term "introduced" really refer to? Brought in by humans and their activities only
(whether on purpose or unintentionally), or in any other ("more natural"?!) way as well? What if the
animals just raft on something and get there without any human influence, is that still considered
an "introduction"? Are there any agreed-upon criteria you know of? (I mean, regarding the technical
term, since the outcome itself can be pretty much the same...)

(2) If an "introduced" species (the "newcommers") happens to survive for, say, 2000 years in it's new
homeland, should one still term that population as "introduced", or just accept it as "indigenous"...
or at least as "permanently present"... or what?
(Of course, 2000 years refers just to the above particular example, it might as well be 100 years or
only 15 years, depending on the species, the circumstances, and the outcome...)

That's an interesting question...I've wondered about this myself.
My personal opinion is that it should only be considered "introduced" if it is intentionally brought by humans. Nobody considers the brown rat "introduced" in the UK anymore althouh it does not originate here...or species of flees and mosquitos...It is part of their natural behavior to parasitise humans like it is natural for the rat to scavange around humans (including ships). So if Eryx (naturally) seeked refuge in a crate of sand because it was attracted onto a human ship by the rats, for example, and was than brought to Sicily by humans is this introduction or natural extend of the distribution? Such natural inter-species introductions happen between other species as well (without human involvement), e.g. when amphibian spawn sticks to the legs of water birds which transport them outside their distribution. So if humans are another species of animal (which they are) why should something that "sticks" to us be considered introduced?

...is this introduction or natural extend of the distribution?
So if humans are another species of animal (which they are) why should something
that "sticks" to us be considered introduced?

That was my question, in a nutshell, thank you.

My personal opinion is that it should only be considered "introduced" if it is intentionally brought by humans.

What about unintentionally, but also by humans? Some 10 or 15 years ago, a load of stones arrived from
the island of Brač to the island of Cres/Lošinj, at the town of Osor, and along with it some Dalmatolacerta oxycephala. Now we have a (very local, for the time being) population of D. oxycephala there, but thriving
and spreading, in perfect coexistence with the local (really indigenous) Podarcis melisellensis. What should
one say about that a decade or a century from now?

So if Eryx (naturally) seeked refuge in a crate of sand because it was attracted onto a human ship by the rats, for example, and was than brought to Sicily by humans is this introduction or natural extend of the distribution?

In the alleged warfare of those times, snakes were caught (in large quantities), put in sealed ceramic jars,
and catapulted at enemy ships or fortresses, to scare away the defenders. The jars would burst at the
impact and the snakes would spread all around... instigating utter panic among the defenders, no doubt.
I've always thought that venomous snakes of any available kind were used for that purpose, which could
explain some unexpected local populations of them two millenia thereafter... So, why should one use e.g.
Eryx jaculus or any other nonvenomous snake to that end?
Well, once the defenders leave in panic, you still want to take over their abandoned ship or fortress - but
not crawling with venomous snakes, if possible. It does make sense. Whether they really organized it like
that, I've never found a clear confirmation in the available historical writings, much as I tried.

'Introduced' can be intentional or unintentional but always anthropogenic. Arrival as unintentional stowaway to a new area is just as unnatural as deliberate release, both for the moved animals as for the newly colonised ecosystem.

Rafting etc. are (uncommon) dispersal methods, not introductions.

After how many years you treat a species as naturalised, is obviously not a hard scientific question. I've seen periods of 50 years or a century being mentioned. But still, that brown rat will always be introduced, regardless of how long ago.

Berislav Horvatic wrote:I've always thought that venomous snakes of any available kind were used for that purpose, which could
explain some unexpected local populations of them two millenia thereafter...

That would mean that the soldiers collecting snakes all know how to tell species apart. Also, I'm guessing that if during a battle someone throws a snake at you, you're not going to sit down and look if you should be scared or not. What puzzles me more is that they would have had to collect a fairly decent amount of Eryx for it to persist, but this should also be settled by genetics - maybe the genetic diversity of the Sicilian population tells us that they all stem from very few ancestors/founders.

'Introduced' can be intentional or unintentional but always anthropogenic.

What about species which natural behavior includes parasitising humans (e.g. flees, ticks, or others)? If such a parasite hitches a ride on some bird species during it's long migration route and then manages to survive at the final destination(which is not it's original range), this will not be considered introduction by that logic. However, if it hitches a ride on a human on that same route and destination it would be considered introduction...? This would make us somehow special... If what you're saying is the correct definition of "introduction" maybe we(humans) should come up with a new term to describe this, something that specifically explains the anthropogenic bit.

Ilian Velikov wrote:What about species which natural behavior includes parasitising humans (e.g. flees, ticks, or others)?

Maybe there's a term for it, dunno. You could throw expensive words like 'epizoic' and 'exogenous' around, I guess. I personally don't really care - it's all human nature trying to fit things into clear discrete categories, while the natural world and life are not clear-cut.

Jeroen Speybroeck wrote:I personally don't really care

Me neither, I'm just having fun discussing it

Jeroen Speybroeck wrote:it's all human nature trying to fit things into clear discrete categories, while the natural world and life are not clear-cut.

Indeed...Silly humans.

Ilian Velikov wrote:

Jeroen Speybroeck wrote:I personally don't really care

Me neither, I'm just having fun discussing it

Me too, but I'd also like to know what the "big shots" offer as definitions - after all, in any science,
one has to have them... Artificial as they might be, we still have to know the meaning of the basic
technical terms we use.

Ilian Velikov wrote:Indeed...Silly humans.

Ilian, either you "surrendered" too easily, or you're teasing the admin a little bit...?

I'm not gonna play, Bero = just google it.

Jeroen Speybroeck wrote:I'm not gonna play, Bero = just google it.

I'm not playing with you or anyone or anything, I'd just like to know - in case biology is a "grownup/adult"
natural science - which I've come to doubt... but I won't elaborate why - not here and now. Let me just
say that it appears to me somewhat "softer" than e.g. physics or chemistry or geology... even meteorology.

I know how to "google", thank you. It doesn't help, not in cases like that.

BTW, I asked Ilian a question, not you. Maybe he would like to "play", that is, have the fun of discussing.
He started very well.