Abstract
Abstract Life-history, geographical barriers, and damming can shape the genetic diversity of freshwater migratory fish, which are particularly vulnerable to anthropogenic impacts. We investigated the genetic diversity of Salminus brasiliensis, a long-distance migratory species that is recognized as an important provider of ecosystem services. We implemented microsatellite analyses to assess genetic diversity and simulate future scenarios for evaluating the long-term viability of dammed and non-dammed populations from the Uruguay River. High levels of genetic diversity were detected for all sampled populations. However, effective population sizes were lower in the uppermost river stretches, where the landscape is highly fragmented. Population structure analysis indicated two spatial genetic populations. It is suggested that this genetic structure preserves populations partially isolated by an ancient natural barrier, instead of being a result of the presence of dams. The simulated genetic scenarios indicated that genetic variability of S. brasiliensis populations from upstream dams could collapse over the years, mainly due to the reduction in the number of alleles. Therefore, besides helping to better understand issues related to the influence of dams on the genetic diversity of migratory fish, our results are especially relevant for driving local fishery policies and management actions for the species conservation.
Highlights
Large freshwater migratory fish species commonly require complex habitats to complete their life cycle (Winemiller, 2005)
Our results suggest that genetic diversity loss is quite inevitable in S. brasiliensis inhabiting the Uruguay River, and that it may compromise the viability of the fragmented populations isolated by dams in the uppermost portion of this hydrographic system in 100 years
Our simulated scenarios of population bottleneck showed that lesser values of genetic diversity (Ae) will be reached in the populations located in the uppermost portion of the dam cascade system (Pop1 and Pop2)
Summary
Large freshwater migratory fish species commonly require complex habitats to complete their life cycle (Winemiller, 2005). Dams can cause substantial disruption to river systems and fish communities (Dudgeon et al, 2006; Vörösmarty et al, 2010) by fragmenting and reducing available habitat for local populations. This scenario favors a reduction of the effective population size, an increase in the genetic drift and inbreeding, and a consequent genetic diversity reduction (Yamamoto et al, 2004; Bessert, Ortí, 2008). The species persistence depends on the ability of its populations to adapt in response to anthropogenic and habitat disturbances (Oro, 2020)
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