Of course I know what you mean. And yes, species' is how I would have typed or written it although it would sound the same as species. I cases like that, I just say "species" but the apostrophe indicates possesive noun. Doesn't it? I dunno. Anyway, I failed english miserably most of my acedemic career anyway. No matter. (here comes the evidence of my failure)

I got big snakes!

(I know better, but speak to the contrary)

I gots big snakes. I do haz big snakes? There. That's better.