Genetic effects of living in a highly polluted environment: the case of the silversideBasilichthys microlepidotus(Jenyns) (Teleostei: atherinopsidae) in the Maipo River basin, central Chile

Abstract

Freshwater systems are one of the environments most impacted by human activity, with pollution being a highly important factor. In Chile, several rivers exhibit varied levels of pollution, one of which is the Maipo River basin where the city of Santiago is located. The silverside Basilichthys microlepidotus (Jenyns) is an endemic fish species that inhabits this basin, thus we hypothesized that pollution has affected gene diversity and migration in populations of B. microlepidotus from the Maipo River basin. The aim of this study was to identify the population structure of B. microlepidotus in this basin and to determine if the populations of the silverside inhabiting polluted sites present differences in gene diversity and gene flow compared to populations inhabiting non‐polluted areas. Using the variability of eight microsatellites, five populations of silverside were detected; three inhabiting non‐polluted sites and two inhabiting polluted sites. From this, it was inferred that B. microlepidotus has been able to tolerate pollution in the Maipo River basin. No differences in gene diversity or migration were detected between polluted and non‐polluted sites but comparison with historical estimation revealed an increase in the current migration rate when all the data from the basin were compared. A reduction in current effective population size was also observed when compared to historical values, and this is probably due to river degradation. Despite the disappearance of other fish species recorded at this basin, our results suggest that B. microepidotus is tolerant to pollution, thus indicating that native species respond differently to this environmental factor.

Liver transcriptome characterization of the endangered freshwater silverside Basilichthys microlepidotus (Teleostei: Atherinopsidae) using next generation sequencing

“…It is a microphagous species, feeding on insect larvae, small invertebrates, filamentous algae and detritus (Duarte et al, 1971). It has been pointed out that it can survive in highly polluted rivers (Vega-Retter et al, 2014). Considering that B. microlepidotus is indicated as an endangered species , future conservation measures will need information about its health, stress responses and adaptive responses to human activity.…”

Signatures of Directional and Balancing Selection in the Silverside Basilichthys microlepidotus (Teleostei: Atherinopsidae) Inhabiting a Polluted River

“…This is not surprising, because the characteristics of the pollutants along the river are different. Vega-Retter et al (2014) showed that the two polluted sites (MEL and PEL) differ in levels of pollution, with clear differences in dissolved oxygen as well as concentrations of copper and molybdenum. Thus it is probable that pollution affects natural populations in different ways, triggering adaptation to local characteristics of the pollution even within a basin.…”

“…1). Vega-Retter et al (2014) found five different populations of silversides in this basin, two located in sites classified as highly polluted (PEL and MEL) and three populations inhabiting five sites classified as non-polluted (PU, IM, PN, MA, SFM; according to the population structure the populations are composed of PU, IM-PN and MA-SFM) according to the British Columbia Water Quality Index (BCWQI). This population structure ( Fig.…”

“…This species inhabits lakes and rivers from 28°to 39°S (Véliz et al 2012); it feeds on insect larvae, small invertebrates, filamentous algae and detritus (Duarte et al 1971;Bahamondes et al 1979) and reproduces from August to January (Comte and Vila 1992). A previous study performed in the Maipo River basin using microsatellite loci showed the presence of genetically distinct populations of B. microlepidotus inhabiting polluted areas of the river and others inhabiting non-polluted sites (Vega-Retter et al 2014). Thus this species and the basin that it inhabits provide a useful model system to study the selective effect of pollution on the genome.…”

Differential gene expression revealed with RNA-Seq and parallel genotype selection of the ornithine decarboxylase gene in fish inhabiting polluted areas

“…This pollution categorization was defined using the British Columbia Water Quality Index 21 based on the attainment of water quality objectives and taking into consideration the natural water quality expected at any given site. Furthermore, Principal Component Analysis indicated that the total dissolved solids, electrical conductivity, chloride, sulfate, molybdenum, ammonium, copper and nitrite were the principal variables accounting for the variance among sites 22 . Water degradation observed in the two polluted sites was the result of different contaminants, such as heavy metals from mining and factories, pesticides from agriculture and dioxins from industrial processes, among others.…”