same species

[The Flying Tench]

How come the same freshwater species can be found in different continents? (eg trout, pike, I think were native fish in America and Europe). Did they maybe start as sea fish and move into fresh water? Or maybe they swam across the Baring Straits?! I don't know if any native Australian fish are the same as for Europe?

[Ken L]

III. Fresh water distributions

Because freshwater is isolated, might expect restricted ranges; but this is not the case (in fact, they often have distributions even broader than terrestrials): How is this explained?

A. Distribution of Fish

B. Distribution of Shells (molluscs)

C. Distribution of Plants (often very wide ranges)

In all cases, dispersal of freshwater organisms depends largely on animal (esp. bird) transport

[Mickm8]

In days of old it was just one land mass.... and then bits broke off!

[Vagabond]

Some species have spread due to colonisation from sea, others due to what used to be called "continental drift" but is now known as plate tectonics. ie Continents splitting apart.

 

Its a huge subject, the geological timing of each continental split vis a vis the evolutionary process being important. ie that's why N American fauna/flora is very like that of Europe, and why S America has similar (but fewer) links with Africa.

 

At the other extreme, Australian fauna/flora is very different from elsewhere, because it split off much farther back in time. NO Native Australian freshwater fish resemble European fishes.

 

The most interesting links are the lungfish. Three continents have them - South America, Africa, and Australia. They have evolved into different species, but have a common ancestor from the time that these three continents were joined.

 

 

In addition to Ken's links, look at http://en.wikipedia.org/wiki/Plate_tectonics which gives the underlying cause.

Edited May 18, 2008 by Vagabond

[The Flying Tench]

Very interesting.

 

Thanks