Re: What species of animal or plants will reproduce with other species?

Hi there

The standard definition of a species is one that has evolved to the extent 
that it can't reproduce successfully with other types of organism. For 
example, if a population of mice were suddenly separated by a mountain 
range (unlikely I know), they would all be the same species until they had 
evolved to become sufficiently different that they could no longer 
interbreed - then they would be two different species. This is called 
speciation and happens due to changes in body structure, behaviour (in 
animals) or other factors such as pollen structure and flowering time (in 
plants). 

However, some closely related species do seem to be able to interbreed 
such as lions and tigers (making 'tigons' and 'ligers' depending on which 
is the mother and which is the father) and more famously horses and 
donkeys which produce mules. However, in all these cases, the offspring 
are sterile and therefore are unable to reproduce further. So, the rule 
remains - separate species can never successfully reproduce and that is 
how species are defined.

You may also read or hear about 'sub-species' - these are populations of a 
species which are becoming different (maybe they are speciating) but are 
still able to reproduce, although they may not do so in nature because 
they have been separated and no longer meet. This is very true of plants 
as many have complicated mixtures of subspecies and species which can be 
difficult to tell apart and which can interbreed to form 'hybrids'.

I hope that answers your question - and adds a bit more interesting 
information too - of course there is much more, especially regarding 
plants!

Bye for now

Dr Dave Hubble, Hampshire, UK