Congeners and conspecificity

Congeners refer to organisms belonging to the same genus or species.

For two individuals to be conspecific, it means that they are from the same species.
Antonym: heterospecific

Reference:
http://en.wikipedia.org/wiki/Congener
http://en.wikipedia.org/wiki/Conspecific

Syntopic

To be syntopic means to be sharing the same habitat as another species and within their geographic range.

Reference:
http://www.practicalfishkeeping.co.uk/pfk/pages/glossary.php?entry_name=Syntopic

Allopatric speciation

Allopatric speciation, may also be referred to as geographic speciation, whereby populations of individuals are separated by a barrier and evolved such that when the barrier breaks down, these two groups no longer have the ability to interbreed.

"Allo" = other
"patra" = fatherland

Reference:
http://en.wikipedia.org/wiki/Allopatric_speciation