When physical oceanography meets population genetics: The case study of the genetic/evolutionary discontinuity in the endangered goliath grouper (Epinephelus itajara; Perciformes: Epinephelidae) with comments on the conservation of the species

Abstract

Epinephelus itajara is one of the marine fish species most threatened for extinction and it is considered to be "critically endangered" by the IUCN. The present study evaluated the genetic diversity of the species and the genetic/evolutionary relationships of its populations along the Atlantic coast of South America. The results indicate relatively reduced genetic variation, re-emphasizing the low adaptive potential of the species. One of the populations presented relatively high degrees of genetic diversity and it is evolutionary isolated from the all other populations. The evidences indicate the existence of two Evolutionarily Significant Units comprising E. itajara in the Atlantic coast of South America and the conservation prospects for the species must take these evidences into account. Highlights ► A low genetic diversity was confirmed in Epinephelus itajara. ► The species is divided into two genetic/evolutionary lineages. ► A possible ESU of E. itajara occurs at the Babitonga bay (Southern Brazil). ► Physical oceanography explains the isolation at the Babitonga bay (Southern Brazil). ► Also a panmictic population occurs in the rest of the Atlantic coast of South America.

Mitochondrial DNA evidences reflect an incipient population structure in Atlantic goliath grouper (<em>Epinephelus itajara</em>, Epinephelidae) in Brazil

“…Despite the small sample size for the southernmost population, at Babitonga (Santa Catarina) the common haplotypes are shared with other population units; this population is not isolated from the others and is characterized by reduced genetic diversity. This finding differs from that of Benevides et al (2014), who used a nuclear marker. This incongruent evidence might suggest possible phenomena of sex-biased demography such as male/ female phylopatry in the region.…”

“…Torres et al (2013) developed a molecular identification protocol for monitoring the fishing of groupers, including E. itajara, E. morio, Mycteroperca bonaci and M. marginata. Using simple repeat sequence markers, Benevides et al (2014) confirmed the low degree of genetic variation in E. itajara populations from ten locations, including the Atlantic coast of South America, and revealed a strong population division in southern Brazil in comparison with populations found in the eastern and northern regions of the country. Silva-Oliveira et al (2008) used a mitochondrial marker to study E. itajara populations on the northern coast of Brazil, while Benevides et al (2014) used a nuclear marker to study populations on the northern and eastern coasts.…”

“…The reduced genetic diversity of the Atlantic goliath grouper has been related to overfishing and the loss of habitats (Silva-Oliveira et al 2008), and the accentuated decline of the populations of this species throughout its area of distribution in recent years (McClenachan 2009, Coleman andKoenig 2010) may exert a negative influence on its genetic diversity in the near future, further underscoring its status as a critically endangered species. Low genetic diversity in E. itajara has been suggested in microsatellite loci (Seyoum et al 2013), segments of immunological genes (Silva-Oliveira et al 2014), and nuclear markers anchored in microsatellite regions (Benevides et al 2014), further reinforcing the threatened status of the species on the Brazilian coast. Koenig et al 2007).…”

“…The long larval phase suggests a considerable dispersal capacity, which may result in a lack of stock structuring on oceanic, regional and subregional scales (Aboim et al 2005). The hypothesis of highly vagile E. itajara larvae is supported by the presence of a broad genetic-evolutional unit along the Atlantic coast of South America (Benevides et al 2014). Larval retention by species with aggregated spawning may be selectively advantageous to ensure the access of larvae and juveniles to necessary resources, but a high degree of dispersal and connectivity may not necessarily ensure homogeneous gene flow (Portnoy et al 2013).…”

Population genetic structure and body shape assessment of Pagrus pagrus (Linnaeus, 1758) (Perciformes: Sparidae) from the Buenos Aires coast of the Argentine Sea

“…Several dynamic factors such as river discharge volume, coastal currents and surface wind may or may not act as a barrier to the displacement of the larvae and establishment of different populations. Despite the lack of clear evidence regarding coastal current dynamics along the coast of South America affecting P. pagrus, previous studies on other species have suggested the role of ocean currents in modeling the genetic structure by promoting specific local larval retention (Benevides et al, 2014).…”