Genetic associations amongst subpopulation of Arapaima gigas

Abstract

Arapaima gigas, also known as pirarucu, is endemic to the Amazon basin. There is currently
considerable effort being made to cultivate this species to reduce pressure on natural populations. We
characterized the diversity and genetic structure of subpopulations of wild and captive A. gigas based on
19 microsatellite loci. Captive subpopulations of A. gigas exhibited less diversity than wild individuals.
We also verified the existence of outlier loci under selective pressure in both subpopulations, indicating
the occurrence of local adaptation in some individuals of A. gigas. Furthermore, we identified a high-level
genetic structure among the subpopulations, with no mixing between subpopulations. The lack of mixing
between populations, the local adaptation, and the genetic structure indicate that these subpopulations
should be managed and isolated to prevent captive individuals from escaping into the wild, which would
reduce the diversity of the wild subpopulations. We suggest a program for the genetic management of
captive subpopulations to avoid the random loss of genetic variability and the selection of
characteristics that are undesirable for commercial and conservation purposes.