Abstract ID: 291

Tree species distribution, endemism, and oligarchy in Amazonian floodplain forests: A species colonization concept for Amazonian white-water floodplains

Amazonian white-water (várzea) floodplain forests are the most species-rich floodplain forests worldwide. Little information is available about tree species distribution along environmental and geographic gradients, as well as about species endemism and oligarchy. The present study was designated to investigate species occurrence and distribution of the most common Amazonian várzea tree species, using species samples available in literature, herbaria, and digital databases available in the Internet. The results indicate that approximately 40% of the investigated tree species can be classified as endemics to Amazonian várzea. Of these endemic tree species, the occurrence of the most part of them is restricted to the highly flooded low várzea (inundation height > 3 m, inundation period > 50 days year-1). Approximately 60% are generalist tree species that also occur in other neotropical ecosystems, such as moist terra firme forest, Atlantic rainforest, Cerrado, Llanos, and Caatinga. Despite the small-scale heterogeneity of the alluvial landscape, the high connectivity of riparian corridors leads to similar, vertically arranged ecological niches across remote várzea forests and, consequently, to a restricted number of highly dominant tree species across the Amazon basin. Species distribution patterns allow for the development of a species colonization concept that suggests that várzea genotypes originate from the adjacent terra firme. Once they tolerate and/or create specific adaptations to episodic inundations, these species are able to colonize the higher parts of the floodplains. Only few of these immigrants developed to endemic species able to colonize the lower parts of the floodplains. The concept further suggests that the moderate hydro-geomorphic disturbance in Amazonian floodplains promotes continuous speciation processes, which may significantly contribute to the exceptional high tree species diversity also in adjacent uplands.

Session:  Biodiversity - Modeling biodiversity, present and future. (A)

Presentation Type:  Oral