[Pytor (OP)]

  Given that any environmental niche will be exploited by life,could we create an environment,as yet unknown and,given enough time see what evolution would fill it with.

[RD]

[charles1948]

  Given that any environmental niche will be exploited by life,could we create an environment,as yet unknown and,given enough time see what evolution would fill it with.

This is an interesting suggestion.  The trouble is that evolution generally takes a long time to work.  At  least it does with big, slow-breeding,  multicellular organisms, such as fish. These took millions of years to evolve into amphibians, then reptiles, and eventually to mammals and birds.  So a research program based on these organisms might take too long to produce practical results.

 Faster results could be expected with smaller organisms such as insects.  Or better still - bacteria.

For example, I've read that some bacteria can survive, and even thrive, in very hostile conditions, such as in the cooling water surrounding a nuclear reactor.  This is an artificial radioactive environment which was "unknown", to use your word, until created by humans in  the last century.  It's interesting that bacteria have been able to occupy this new niche.

How far could the bacteria be "pushed", in terms of increasing radiation in the niche, before it became untenable to them.  Would stronger, more radiation-resistant bacteria continually evolve? Or would they reach an end-point where adaptation was no longer possible.  What would the maximum dosage of radiation be for bacteria in the form that we know them.  Would the bacteria evolve into some new form, as yet unknown?

I'd be rather surprised if experiments along these lines haven't been conducted.  Perhaps not just for scientific purposes, but with some military aim in view.  Is there any evidence of it?
 

[Bored chemist]

Is there any evidence of it?

https://en.wikipedia.org/wiki/Dog_breed

[RD]

... I've read that some bacteria can survive, and even thrive, in very hostile conditions, such as in the cooling water surrounding a nuclear reactor  ...

Some fungi are loving it ... https://en.wikipedia.org/wiki/Radiotrophic_fungus