Contribution to the taxonomic elucidation of the Geonoma maxima complex (Arecaceae) in Central Amazonia, Brazil

Abstract

Geonoma maxima (Poit.) Kunth is an example of a species complex, among many others restricted to Neotropical rain forests, which contribute to their high species diversity. Using environmental, morphological, karyological, and molecular data, we aim to test the taxonomic circumscription of 3 of the 11 G. maxima subspecies defined in the latest taxonomic treatment. We evaluated 217 samples of G. maxima complex from Ducke Reserve in the state of Amazonas, Brazil. Environmental preferences were significant at the 0.1% level. Subspecies maxima occurred in the slope, subsp. chelidonura in the floodplain, and subsp. spixiana in the plateau. Leaf morphology and height were different for each subspecies, but not leaf anatomy. The karyotypes of subspp. c helidonura and maxima were symmetrical with 2 n = 28 chromosomes, 16 metacentric and 12 submetacentric. Molecular analysis revealed two groups, one comprised subspp. maxima and chelidonura, and the other formed exclusively by subsp. spixiana. At Ducke Reserve, it is clear that the three subspecies are easily recognizable morphologically and ecologically, and it is likely that they do not interbreed locally. However, if these subspecies are analyzed on a larger geographic scale, it may not be possible to separate them.