Western Amazonia harbours one of the richest palm floras of the Neotropics. About 121 palm species and 33 genera occur in this region. Approximately 40% of these species and three monotypic genera ( Aphandra , Itaya and Wendlandiella ) are restricted to western Amazonia. Bactris (23 spp.), Geonoma (20 spp.), Attalea (17 spp.), Astrocaryum (11 spp.) and Oenocarpus (7 spp.) are the most well-represented genera in the region. Palms, however, are not homogeneously distributed across western Amazonia. A major change in palm composition occurs between Yasuní (eastern Ecuador) and Iquitos (eastern Peru). Species that are very abundant on the unflooded forest of Yasuní, such as Iriartea deltoidea or Prestoea shultzeana , are replaced by Socratea exorrhiza , Lepidocaryum tenue var. tenue or Iriartella stenocarpa in the Iquitos-Pebas region. Moreover, the distribution ranges of the majority of eastern Ecuadorean palms reach the Iquitos region, but the converse is not observed. Censuses of palm communities along transects, studies of microhabitat preferences of Oenocarpus bataua and documentation of the distribution limit of Astrocaryum species in the intermediate zone provide new insights on the floristic change that is occurring. Modern ecological constraints and geological history during the Cenozoic may explain the observed variations.

The fatty acid (FA) composition of Oenocarpus bataua oil from 38 samples collected over a large geographical range (i.e. French Guiana and Peru) was analyzed. Fifteen fatty acids were obtained from the mesocarp of this palm species. Oleic (72.7%) and palmitic (18.1%) acids were the predominant FAs. Minor FAs were cisvaccenic acid (2.3%), linoleic acid (1.9%), stearic acid (1.7%), palmitoleic (0.9%) and alpha-linolenic acid (0.8%). The mean lipid content of the dry mesocarp was 51.6%. The O. bataua oil samples analyzed were remarkably rich in a-tocopherol. By contrast, the other fractions of the unsaponifiable matter (sterols, carotenoids) did not show any noteworthy specificity in comparison with common vegetable oils. However, the particularly high percentage in D5-avenasterol of O. bataua oil could serve as a marker for its authentication. Results are discussed in terms of the potential nutritional value of O. bataua oil.

We review resilience to natural and anthropogenic disturbance of palm populations and communities in tropical America. Response of palms to disturbance depends on their morphological traits, their reproductive strategies and the impacts of these traits and strategies on phenology and gene flow. Human impact induces changes in genetic structure, increasing endogamy and genetic drift in fragmented populations. Forest fragmentation and harvest of palm organs are well documented whereas effects of intermediate disturbance like selective logging, hunting or fire remain poorly known. We recommend emphasis on long-term experiments and on the use of mechanistic approaches in future research to facilitate integration of available data into a theoretical ecological framework.

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