Chocolate lowland climate in the narrow band of latitudes where cacao is grown (20 degrees north and south of the equator), the commercial company Mars, Incorporated and the University of California, Berkeley are conducting genomic research in 2017–18 to improve the survivability of cacao plants in hot climates. Chocolate is made from cocoa beans, the dried and fermented seeds of the cacao tree ("Theobroma cacao"), a small, 4–8 m tall (15–26 ft tall) evergreen tree native to the deep tropical region of the Americas. Recent genetic studies suggest the most common genotype of the plant originated in the Amazon basin and
Madeira-Tapajós moist forests excelsa" and "Duckeodendron cestroides". At one time the endemic tree "Polygonanthus amazonicus" grew near Maués, the western limit for the emergent "Dinizia excelsa" and the eastern limit for the "Theobroma cacao". The Tapajós basin is the eastern limit of "Theobroma microcarpum". The "Physocalymma scaberrima" has red hardwood used by furniture makers. The montane forests of the upper Marmelos and middle Tapajós hold "Hevea camporum", "Euterpe longibracteata", "Huberodendron ingens" and "Brachynema ramiflorum". Further south in Mato Grosso there are forests in the transition between the Amazon and cerrado biomes. 183 species of mammals have been reported, including 90 bat species and