Looking for a home in foreign waters: population genetic structure of the introduced Arapaima in Bolivia

Establishment of invasive aquatic species is increasing globally due to factors related to globalization and accelerated trade between regions. Such invasions and subsequent establishment generally cause ecosystem disturbance with occasional local and/or regional socioeconomic impacts. The paiche (tentatively identified as Arapaima gigas), one of the largest fish in the Amazon, was introduced into Bolivia via Peru in the 1960s and has generated significant changes in Amazonian fisheries. In recent years, it has been proposed that the genus Arapaima is composed of different species distributed along the Amazon Basin. The present study evaluated the genetic variability of the paiche in the Bolivian Amazon Basin (sub-basins of the Orthon, Madre de Dios and Beni rivers) using nuclear (nDNA- microsatellites) and mitochondrial (mtDNA NADH and CO1) genetic markers to determine species identity and population structure. Microsatellite DNA analysis suggested that the three populations corresponding to geographic sub-basins are genetically distinct. The genetic distance between populations was not significantly related to the geographic distance between collection sites. We suggest that the founder population in Bolivia was composed of a limited number of individuals that subsequently dispersed in search of environmental conditions similar as those habitats from which they were extracted. Planning for the sustainable use of the species by fisheries should consider the existence of different populations in the Bolivian sub- basins. Recruitment seems to depend on exchanges between nearby surrounding aquatic habitats rather than between sub-basins.