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Present-day species of piranha result from a marine incursion into the Amazon Basin
Date:12/3/2007

, these piranhas could finally have dispersed downstream, finding their way back to the Amazons lowland plain which would have served as a gathering ground for biodiversity. What now remains to be found are the ecological parameters that could have favoured the diversification of piranha populations so confined to the upper reaches of the river network.

One of the hypotheses advanced highlights water quality as a factor in stimulating ecological and morphological differentiation of species. The field survey observations indicated that some of the species were highly localized, in both geographical and ecological terms. For example, Serrasalmus hollandi is mostly found in turbid, sediment-laden waters flowing down from Andean mountain streams. In contrast, a new species the biologists discovered, lives in the same hydrographic basin but only in rivers with crystal-clear waters bearing very little sediment content.

However, water quality cannot be considered as the sole factor behind speciation, seeing that a third piranha species was found living in either of these two categories of river. The research results as a whole suggest that the superimposition of factors linked to geographical history and ecological conditions, intervening at different spatial and temporal scales, is responsible for the diversification of the piranhas. This is an evolutionary progression which should be transposable to other fish communities inhabiting South American waters.


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Contact: Gregory Flechet
fichesactu@paris.ird.fr
33-014-803-7607
Institut de Recherche Pour le Dveloppement
Source:Eurekalert

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