Narrowing the geographic gap between the disjuncts Aristolochia subsect. Pentandrae and the A. lindneri group (Aristolochiaceae): new records of A. pentandra and A. stuckertii in Brazil

Aristolochia subsect. Pentandrae is a monophyletic assembling of nearly 50 species distributed across the southern USA, Mexico, Guatemala and Belize, and the Antilles. The most consistent characters of the subsection are the pentamerous androecium and gynoecium, two traits not found elsewhere in the family Aristolochiaceae. Here, we report the first record of A. pentandra in Brazil, which also represents the first continental occurrence of Aristolochia subsect. Pentandrae in South America. This finding significantly expands the geographic range for the entire subsection. Here we fully document and discuss the morphology, conservation, and biogeography of this unexpected collection of A. pentandra in the Amazon basin. Additionally, we report the presence of A. stuckertii in Brazil, one of the hexandrous species belonging to the ‘A. lindneri group’, an informal group of five species from central and southern South America, proposed as sister to the subsection Pentandrae. The discovery of A. pentandra in Brazil significantly narrows the geographical disjunction between these two closely related clades.