Low mtDNA diversity in a highly differentiated population of spinner dolphins (Stenella longirostris) from the Fernando de Noronha Archipelago, Brazil

Abstract

Spinner dolphins (Stenella longirostris, Gray 1828) are widely distributed in tropical waters around the world. Although they occur in large, pelagic groups in the Eastern Tropical Pacific, elsewhere in the Pacific they are found in small and genetically isolated populations associated with islands. This species is considered to be "Least Concern" (LC) by the World Conservation Union (IUCN). To assess genetic diversity and population structure of an island-associated population in the South Atlantic Ocean we surveyed 162 spinner dolphins throughout the Fernando de Noronha Archipelago of the northeast coast of Brazil using ten microsatellite loci and sequencing a 413-bp section of the mitochondrial DNA (mtDNA) control region. Eleven mtDNA haplotypes were identified and haplotype diversity (h) and nucleotide diversity (π) were 0.3747 and 0.0060, respectively. Median-Joining Network revealed the presence of two very divergent haplotypes and F-statistics indicated some heterogeneity between two sampling years. All microsatellite loci were polymorphic (H o : 0.767; H e : 0,764) but, revealed no detectable substructure. We also compared the mtDNA haplotypes from Noronha to 159 haplotypes representing 893 individuals from 14 locations worldwide. We found that the two common haplotypes from the Fernando de Noronha Archipelago were absent in all other populations. These comparisons showed that Noronha spinner dolphins are likely more differentiated than other island populations, suggesting that they form societies with strong site fidelity mediated by females.

Mitochondrial diversity and inter-specific phylogeny among dolphins of the genus Stenella in the Southwest Atlantic Ocean

“…Low levels of diversity were described in the population of S . longisrotris in the Fernando de Noronha archipelago of Brazil (h = 0.374; π = 0.044) [ 1 ] while high levels were found for S . clymene (h = 1.00; π = 0.02) [ 2 ], and for S .…”

“…The Mitochondrial DNA (mtDNA) is an effective molecular marker for the quantification of genetic diversity, and together with nuclear markers to detect reciprocal hybrids [ 1 , 24 ]. Mitochondrial DNA is maternally inherited, has high mutational rates and it is easy to isolate and characterize [ 30 , 31 ].…”

Low Genetic Diversity of the Endangered Franciscana (Pontoporia blainvillei) in Its Northernmost, Isolated Population (FMAIa, Espírito Santo, Brazil)

“…Molecular markers of the mitochondrial DNA (matrilinearly inherited) such as the control region (D-loop) and of the nuclear DNA (biparentaly inherited) such as microsatellite loci largely used in cetacean population genetics studies (Cunha et al, 2014;Gariboldi et al, 2015;Donato et al, 2019;Faria et al, 2020). These molecular markers can be used to access the genetic diversity of a population, to study the differences between the populations of a species and also to determine taxonomic relationships (Frankham et al, 2006).…”

“…D-loop is a region of mitochondrial DNA that shows some advantageous traits for these types of studies, such as being highly variable, having a small population size by being haploid, and lacking recombination (Frankham et al, 2006). Microsatellites or SSRs (Simple Sequence Repeats) have been extensile used for assessing nuclear DNA polymorphism for different species (Costa-Urrutia et al, 2012;Lima et al, 2017;Faria et al, 2020). They show codominance and high levels of polymorphism with many alleles per locus (Frankham et al, 2006).…”

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“…When compared with other species of dolphins, threatened or not, franciscanas from FMAIa still have one of the lowest haplotype genetic diversity found (Rosel and Rojas-Bracho, 1999;Chivers et al, 2002;Parsons et al, 2002;Caballero et al, 2010;Hamner et al, 2012;Faria et al, 2020; Table 6).…”