Complex sentence: The majority of the Tatar population are Volga Tatars, native to the Volga region, and the Crimean Tatars of Crimea, there are smaller groups of Lipka Tatars and Astrakhan Tatars in Europe and the Siberian Tatars in Asia.
Split into simpler sentences: The majority of the Tatar population are Volga Tatars, native to the Volga region, and the Crimean Tatars of Crimea. There are smaller groups of Lipka Tatars and Astrakhan Tatars in Europe and the Siberian Tatars in Asia.