Genetic characterisation of populations of the critically endangered Goliath grouper ( Epinephelus itajara, Serranidae) from the Northern Brazilian coast through analyses of mtDNA

Abstract

The Goliath grouper (Epinephelus itajara) is one of the most endangered species of fish of the subfamily Epinephelinae. Slow to develop and mature, and dependent on mangrove habitats for breeding, the species also suffers intense harvesting, which has reduced drastically in numbers in many areas. To contribute to the understanding of the characteristics of E. itajara populations, we conducted a molecular genetics study of the species, focusing on populations from the Northern Brazilian coast. The mtDNA control region (D-loop) of 116 individuals from five localities (Bragança, Ajuruteua, Parnaíba, Fortaleza and Natal) was analysed, and a sequence of 499 base pairs identified. Analyses of the sequences indicated that genetic variability was generally lower in E. itajara than in other endangered species of the genus. AMOVA found no significant grouping structure among the populations. Nested Clade Analysis revealed a significant association between genetic variability and geographic distribution among only three populations (Ajuruteua, Parnaíba and Natal). Genetic diversity was higher in populations from the Amazon region, which may be related to the better conservation of mangrove habitats in this area. Therefore, the present study could be used for the implementation of conservation and management measures in order to protect and consolidate these populations.

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

“…However, this genetic structuring-indicated by the Φ ST value-is much lower than that found in other groupers, such as Epinephelus labriformis (F ST ≤0.661, p=0.001) (Craig et al 2006) and E. akaara (F ST ≤0.379, p<0.001) (Chen et al 2008), although the population structure is similar to that found in other species of reef fish (Zhang et al 2006, Drew and Barber 2012, Cunha et al 2014. Silva-Oliveira et al (2008) found significant genetic differentiation in pairwise F ST values for E. itajara between Parnaíba and both Bragança and Natal, but did not detect structuring between Bragança and Natal. The significant differences in F ST and the complex haplotype network found for the Bragança, Parnaíba, Caravelas and Conceição da Barra population units indicate that these locations are not isolated.…”

“…These sequences refer to specimens collected in Bragança + Ajuruteua (Pará: PA) (N=92), called in this study by 'Bragança', Parnaíba (Piauí: PI) (N=12), Fortaleza (Ceará: CE) (N=2) and Natal (Rio Grande do Norte: RN) (N=9) (Silva-Oliveira et al 2008) (Table 1).…”

“…These genetic diversity values differ from the high values reported by Rivera et al (2004) for E. quernus in Hawaii (USA) and by Souza et al (2015) for Cephalopholis fulva (Epinephelidae) on the Brazilian coast, although they are similar to the values reported for other species of reef fish (Zhang et al 2006, Hobbs et al 2013). 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.…”

“…The first molecular data on E. itajara highlighted the phylogenetic position of the species in the subfamily (Epinephelidae sensu stricto) (Craig and Hastings 2007) and the genetic features of some populations in northern Brazil, based on the mitochondrial control region (Silva-Oliveira et al 2008). It was subsequently determined that goliath groupers in the Pacific constitute a cryptic species (E. quinquefasciatus) in comparison with the populations of the Atlantic (E. itajara), as demonstrated by their cytochrome B sequences (Craig et al 2009).…”

“…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. Both studies have provided important insights into the population genetics of the species.…”