The Amazon Basin contains the largest number of scientifically described freshwater fish species in the world: 2,257 or 15% of the total number of known freshwater species. According to a new study, however, this vast biodiversity is unevenly distributed and follows a completely unexpected pattern.
The study was conducted by researchers affiliated with Amazon Fish, an international collaboration that is supported by São Paulo Research Foundation—FAPESP and is building a high-quality database on the freshwater fish species in the Amazon Basin.
Distribution - Model - Amazon - Fish - Researchers
According to the distribution model developed by Amazon Fish researchers, species richness is higher upriver in the western part of the basin than downriver in the eastern portion, which includes the mouth of the Amazon River. This is the reverse of the diversity gradient usually observed in river basins.
The Amazon originates in the Andes not far from the Pacific Ocean in the west of South America and flows into the Atlantic in the east.
Scientists - France - Development - Research - Institute
Led by scientists from France's Development Research Institute (IRD) and ERANet-LAC, a network of researchers from the European Union, Latin America and the Caribbean (LAC), the consortium involves collaborators in the Amazon Basin countries (Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru and Venezuela) as well as Belgium and the United States. The latest results are published in the journal Science Advances.
"According to the classic diversity distribution pattern, species richness is higher near the river estuary, where water flow is greater, therefore supporting a larger number of species. However, our data show a reverse gradient for the Amazon Basin, with the highest species richness in the western portion, west of the Purus Arch relatively near Manaus. We also show that fish species are not evenly distributed across the basin and that endemic species, for example, are concentrated in the upstream portion of the major rivers, such as the [Amazon tributaries]...
(Excerpt) Read more at: phys.org