EG The mule isn't a species, its a hybrid.
In other words, unless they errata it so that the Nidorans can have homosexual reproductive sex with each other (which would be awesome!), they are both either technically one species or both are not species.
I think this could be a good opportunity to get the first naturally homosexual pokemon XD. I mean, other than male Gardevoirs.
I see the major response is, too late. The thing is, Pokemon has gone back and changed things in the past to upgrade them.
Remember when Magneton was only an electric type?
How about when Charizard was incapable of using the move fly?
What about when a male and female Pikachu looked exactly the same?
With almost every generation Pokemon has fixed some things that they knew needed to be looked at.
According to their dex entries, which always refer to them as the male and the female of the species, they are in fact the same species, unlike say Volbeat and Illumise (as brought up by Roronoa Zorua) which are only closely related species.
True enough, It was before breeding even became part of the game, It isn't so bad the way it is, it is just basically a more in depth seperation of genders than the other pokemon.
Charmeleon - It is very hotheaded by nature, so it constantly seeks opponents. It only calms down when it wins. (pokedex)
Illumise will give birth to a male Volbeat, just like a Nidoran(f) will give birth to a Nidoran(m), no matter who their sexual partner is.
They are the same.
I'll breed a female Eevee with a male Pikachu...but I'll never get a Pikachu. That's what sets the Nidorans and Volbeat/Illumise apart from most of the other pogeys.
And adding moves has and will probably always happen.
I don't want the change, because they both look different, learn different moves (I think) and it would mess up the count.
And yeah, Pikachu did change, along with half of the others. But I believe that is only for aesthetic difference, and has nothing to do with game play.
The inconsistency is already remarked on within the games: people didn't know that Pokemon had genders, so they were marked as different species. We may well consider them the same species, but they've already gained separate Dex entries. It works in-universe and out of universe. Why mess with that?
"You know that dragons are mythical Pokémon! They’re hard to catch and raise, but their powers are superior!" - Lance
Princess of Hoenn id peperit.