Abstract
Mechanisms related to ecological or sexual selection have favoured
sympatric speciation events in African and Central American lake
cichlids. Allopatric divergence is the predominant speciation process
observed in Amazonia, although, to the best of our knowledge, no study
to date has attempted to determine whether speciation process could
exist under sympatric conditions in Amazonian cichlids. The
Apistogramma agassizii species complex is an excellent model for
investigating the existence of sympatric divergence events in the
Amazon, as it shares many common life history characteristics with
African Haplochromine cichlids in which sympatric speciation mechanisms
are well documented. The genetic structure of A. agassizii was
analysed by genotyping 889 individuals with ten microsatellite loci,
collected from 26 sites distributed among small streams in 11
micro-basins in a very small portion of the Peruvian Amazon. It revealed
22 genetic populations identified according to panmictic criteria
(FIS estimator) and strongly differentiated:
FST estimator (0.034 to 0.356). Such a strong genetic
structuring on such small geographical areas has never been demonstrated
before in an Amazonian fish. Several of these populations may have
diverged sympatrically and repeatedly in small stream networks. The
results are discussed with respect to divergence processes, including
sympatric speciation, that may be associated with the observed genetic
structure.