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Abstract:
Floodplains are ecosystems, which oscillate between terrestrial and
aquatic phases. Therefore, their biodiversity corresponds to the sum of
species living in the aquatic-terrestrial transition zone and permanent
aquatic and terrestrial habitats within the floodplain, e.g., permanent
water bodies and tree canopies. Major factors determining total
biodiversity are number of species and their abundance in the connected
permanent aquatic and terrestrial ecosystems, the habitat diversity
inside the floodplain, the physico-chemical conditions of soils and
water, the type of flood pulse driving the system, the actual climate
and the paleoclimatic conditions. Biodiversity in different plant and
animal groups in floodplain ecosystems varies strongly because of
differences in their genetic variability resulting in different levels
and ranges of adaptations to the flood pulse. Diversity depends in part
on speciation in the headwaters, where populations are separated from
each other because gene flow up and down river hinders speciation in the
floodplains along the main channels. Also lateral migration of
terrestrial organisms into the floodplain and adaptation of life cycle
and reproductive strategies to the flood pulse seem to be important
mechanisms for speciation. In the Neotropics, more than two million
square kilometers are covered by various types of floodplains. Examples
of the impact of the different factors on species diversity of selected
plant and animal groups are given and the importance of floodplain
ecosystems for total species diversity and speciation in the Neotropics
is discussed.
