Mauritia flexuosa palm swamp communities: natural or human-made? A palynological study of the Gran Sabana region (northern South America) within a neotropical context

Abstract

Mauritia flexuosa L.f. is one of the more widely distributed neotropical palms and is intensively used by humans. This palm can grow in tropical rainforests or can develop a particular type of virtually monospecific communities restricted to warm and wet lowlands of the Orinoco and Amazon basins. It has been proposed that, during the Last Glacial Maximum (LGM), the Mauritia swamp communities were restricted to the core of the Amazon basin from where they expanded favoured by the Holocene warmer and wetter climates. It has also been suggested that some of these palm communities might have been the result of human dispersal during the last millennia. Here, we evaluate both hypotheses using the case study of the Venezuelan Gran Sabana (GS)

Rivers shape population genetic structure in Mauritia flexuosa (Arecaceae)

“…Barlow, Gardner, Lees, Parry, and Peres (2012) found a relationship between sites of Amazonian Dark Earth (ancient, anthropogenic fertile soils) and greater plant species diversity and geographic distribution of some species in comparison with sites without anthropogenic effects. Clement (1999), Rull and Montoya (2014), and Thomas, Alcázar Caicedo, McMichael, Corvera, and Loo (2015) have shown that human populations in the Amazon have transformed its physical landscape and transported plant species large distances. The genetic and spatial distribution of Bertholletia excelsa (Brazil nut), for example, is strongly linked to areas populated by indigenous groups in Amazonia (Thomas et al., 2015).…”

“…The genetic and spatial distribution of Bertholletia excelsa (Brazil nut), for example, is strongly linked to areas populated by indigenous groups in Amazonia (Thomas et al., 2015). Rull and Montoya (2014) found the distribution of pollen of M. flexuosa linked to millenarian charcoal, suggesting that these came from fires made by local communities for hunting and food preparation.…”

“…This palm is also used for raw material for construction and for different handicrafts (Santos & Coelho‐Ferreira, 2011) and its fruits, leaves, and seeds are sold widely in markets (Gilmore, Endress, & Horn, 2013). Mauritia flexuosa has been termed a “hyperdominant” species (Steege et al., 2013), in which population densities are five times higher than expected by chance, and that has recently been attributed to human use and tending practices associated to its use (Levis et al., 2017; Rull & Montoya, 2014). …”

Paleoecology as a guide to landscape conservation and restoration in the neotropical Gran Sabana

“…2). During the last 2000 years, Mauritia swamps have experienced a remarkable expansion because they are not burnt by indigenous people, who use this palm for multiple purposes (Rull and Montoya 2014 In summary, we have identified three general ecological states since the Late Glacial: (i) a forest-shrubland-savanna mosaic dominated by ligneous communities during the Younger Dryas, (ii) extended treeless savannas with gallery forests during most of the Holocene, and (iii) treeless savannas with gallery forests and Mauritia palm swamps during the last 2000 years. It is possible that the number of ecological states will increase as further studies on glacial and former times are conducted.…”

“…Most of the Gran sabana is covered by treeless savannas, with forestsavanna mosaics at the edges and gallery forests along rivers. A special type of gallery forest is the emblematic palm swamp of Mauritia flexuosa, locally known as "morichal" (Rull and Montoya 2014). the Gran sabana is part of the Canaima National Park, in the headwaters of the Caroní River, a tributary of the Orinoco that is exploited for hydroelectric power.…”