Wild Relatives of Guaraná (<i>Paullinia cupana</i>, Sapindaceae) in Southwestern Brazilian Amazon

Abstract Paullinia species are generally laticiferous, woody climbers with a pair of watch-spring tendrils at the middle of the inflorescence, stipules, compound leaves with mostly pinnate organization, zygomorphic flowers with white corollas, septifragal capsules, and black or dark brown seeds with a white arillode. Paullinia is a Neotropical genus with approximately 220 species, one of which (P. pinnata) is also naturally found in Africa and Madagascar. Currently, 99 species are listed for Brazil, most of which are found in forest formations. The Amazon and the coastal Atlantic Forest are the two Brazilian biomes that hold the greatest diversity of Paullinia, with 73 and 26 species respectively. Surprisingly, nearly half of the Brazilian species of Paullinia (45 species, five new records for Brazil) are recorded for the Amazonian state of Acre. In the present work, we provide keys and brief species descriptions to identify the species of Paullinia found in the state of Acre. We also provide information on their distributions within Acre, and within their total range. It is noteworthy that about 70% of the species had their distribution restricted to the Amazonian domain and 44% are restricted to southwestern Amazonia, suggesting this region is a center of diversity for the genus.