Complex sentence: Starchy root vegetables are important staple foods, particularly in tropical regions, overshadowing cereals throughout much of West Africa, Central Africa, and Oceania, where they are used directly or mashed to make foufou or poi.
Split into simpler sentences: Starchy root vegetables are important staple foods, particularly in tropical regions. They overshadow the cereals throughout much of West Africa, Central Africa, and Oceania, where they are used directly or mashed to make foufou or poi.