Genetic Diversity of the Endangered Neotropical Cichlid Fish (Gymnogeophagus setequedas) in Brazil

Abstract

Gymnogeophagus setequedas is a rare and rheophilic species of tribe Geophagini, considered endangered in Brazilian red lists. Its previously known geographical distribution range was the Paraná River basin, in Paraguay, and a tributary of the Itaipu Reservoir in Brazil. Since its description no specimens have been collected in the original known distribution area. However, recent records of G. setequedas in the lower Iguaçu River, in a region considered highly endemic for the ichthyofauna, extended the known geographical distribution and may represent one of the last remnants of the species. The aim of this study was to estimate the genetic diversity and population structure of G. setequedas, using microsatellite markers and mitochondrial haplotypes, in order to test the hypothesis of low genetic diversity in this restricted population. Muscular tissue samples of 86 specimens were obtained from nine locations in the Lower Iguaçu River basin, between upstream of the Iguaçu Falls and downstream of the Salto Caxias Reservoir. Seven microsatellites loci were examined and a total of 120 different alleles were obtained. The number of alleles per locus (NA) was 17.429, effective alleles (NE) 6.644, expected heterozygosity (HE) 0.675, observed (HO) heterozygosity 0.592, and inbreeding coefficient (FIS) 0.128. Twelve haplotypes in the D-Loop region were revealed, with values of h (0.7642) and π (0.00729), suggesting a large and stable population with a long evolutionary history. Thus, both molecular markers revealed high levels of genetic diversity and indicated the occurrence of a single G. setequedas population distributed along a stretch of approximately 200 km. The pattern of mismatch distribution was multimodal, which is usually ascribed to populations in demographic equilibrium. Nevertheless, the construction of a new hydroelectric power plant, already underway between the Salto Caxias Reservoir and Iguaçu Falls, could fragment this population, causing loss of genetic diversity and population decline, and for this reason it is necessary to maintain the Iguaçu River tributaries and downstream area from the Lower Iguaçu Reservoir free of additional dams, to guarantee the survival of this species.

Ichthyofauna in the last free-flowing river of the Lower Iguaçu basin: the importance of tributaries for conservation of endemic species

“… Gymnogeophagus taroba , a species of fast waters ( Paiz et al 2017 ), is widely distributed in the studied area. However, with the construction of the new hydroelectric reservoir, the species can disappear in the flooded area, and its distribution can be fragmented, which will lead to loss of genetic diversity and a population decline ( Souza-Shibatta et al 2018 ).…”

Population genetic structure of the yellow catfish (Pelteobagrus fulvidraco) in China inferred from microsatellite analyses: implications for fisheries management and breeding

“…However, this is not always the case for species that have experienced severe population reductions due to anthropogenic effects. High levels of genetic diversity were usually found in populations of several endangered marine and freshwater fish such as roughskin sculpin ( Trachidermus fasciatus ) and cichlid fish ( Gymnogeophagus setequedas ) (Li, Xue, Gao, & Liu, 2016; Souza‐Shibatta et al, 2018). The high levels of genetic diversity may be the result of relatively large contemporary population sizes, which prevent genetic drift effects.…”

Molecular Inferences on Scomberomorus brasiliensis, From the Western South Atlantic, Based on Two Mitochondrial Genes

“…Given the fact of S. brasiliensis is one of the most harvested marine fish species on the Brazilian coast we suggest that population of the southwestern Atlantic may correspond to a single genetic stock, and should thus be treated as a unit. The genetic variability observed in the S. brasiliensis population sampled in the present study is important for the definition of effective conservation strategies, with the primary objective of mediating the decline of the population and guaranteeing the sustainability of this fishery resource (Ward, 2000;López et al, 2010;Souza-Shibatta et al, 2018;Córdova-Alarcón et al, 2019). Given this, further research on the S. brasiliensis populations should adopt a multi-locus approach integrating microsatellites, SNPs, and RADseq (see Siccha-Ramírez et al, 2018), which would complement the findings of the present study, based on two mtDNA loci.…”