The climate of most lowland zones is arid and semiarid. Riparian zones in arid and semiarid environments have been called biodiversity hotspots. Arid deserts receive between in a year and semiarid deserts between . Cape ground squirrels live mainly in arid or semiarid areas. Brazil has five climatic regions&colon; equatorial, tropical, semiarid, highland tropical, and subtropical. The caper bush requires a semiarid or arid climate. Sorghum is well adapted to growth in hot, arid or semiarid areas. The climate is semiarid in moisture and subtropical in temperature. Pigeon pea is an important legume crop of rainfed agriculture in the semiarid tropics. "Cucurbita foetidissima" requires little water and grows best in semiarid and arid environments. Rainfall was seasonal, alternating between semiarid and mesic conditions. "Myrmecocystus" nests are found in a variety of arid or semiarid environments. Traces of these events are reflected in ratite distribution throughout semiarid grasslands and deserts today. In the United States, "Prosopis" has become the dominant woody plant on of semiarid grasslands. Most species, however, occupy semiarid habitats.