Genetic diversity and origin of a fish population recently colonizing a reservoir: The case ofBasilichthys microlepidotus, central Chile

Abstract

Freshwater ecosystems are among those most affected by human activity. Constructing artificial reservoirs can change freshwater biodiversity, thereby impacting genetic diversity (GD), which is crucial to population-level adaptation. The Maipo River basin, inhabited by the endemic silverside Basilichthys microlepidotus, is one of Chile's most impacted freshwater systems. In this basin, the species is divided into five populations. Recently, a new population was discovered in the reservoir Laguna Esmeralda (LE). We hypothesized that LE silversides possess less GD than other populations and originated from a single basin population. Our evidence shows that the LE is a genetically isolated population with evidence of low genetic variation, but not showing signals of bottleneck or significant reduction in GD. Results consistently identified two sites as unlikely to be the origin of the LE silverside population, suggesting that it was established by the immigration of many individuals from the other three populations.

Genome scans reveal signals of selection associated with pollution in fish populations of Basilichthys microlepidotus, an endemic species of Chile

“…The site designated as MEL showed the most remarkable results in terms of diversity indices, possibly due to the considerable influx of immigrants, mainly from the PEL and SFM sites. Previous studies of the same populations using microsatellite markers have consistently shown a similar trend: a relatively low rate of self-recruitment in the MEL population, which is the lowest of all populations, with immigration coming mainly from the PEL and SFM populations 22 , 23 . It is noteworthy that, despite the considerable migration from PEL and from SFM in MEL, no recognisable genetic homogeneity could be detected.…”