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

Geonoma maxima is an example of a species complex, among many others restricted to Neotropical rain forests, and which contribute to their high species diversity. Using environmental, morphological, karyological, and molecular data, we aim to test the taxonomic circumscription of three 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 of 0.1% level. Subsp 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 chelidonura and maxima were symmetrical with 2n=28 chromosomes, 16 metacentric and 12 submetacentric. Molecular analysis revealed two groups, one comprised by subsp 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.