With the new episode today, the mane six consists of all five different pony races.

Those races include Unicorn, Pegasus, Earth Pony, Alicorn, and the Semi-permanent Batpony.

In the first season the ratio of species was even with there being two of each "common" pony types

and this ratio lasted until the season three finale. Now Earth Ponys are the dominant species within the Mane Six.

Wonder if they will undergo some change...