As far as I know, the word "species" can pronounced either as spee-sheez or as spee-seez. I understand that neither of these is incorrect: they're just two different ways to say the same thing. I also know that the second one is pretty much only used in the US. Not being a speaker myself, I'd like to know: is this a regional variation, or is it just something that depends on the speaker?
The Received Pronunciation (which is the "British Standard", in a way, the one which is also exported) suggests the first one "spee-sheez". Source: Oxford English Dictionary
The US pronunciation accepts both. Source: Macmillan Dictionary
Probably the biologists would use the second one, as internationally there is more consensus on that variant. Also, it comes from ecclesiastical Latin, where the /ˈspiʃiz/ pronunciation was used.
There is more likely a professional/academical difference in pronunciation, than a geographical one, as the word is not everyday language.