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

Abstract

The genus Stenella is comprised of five species occurring in all oceans. Despite its wide distribution, genetic diversity information on these species is still scarce especially in the Southwest Atlantic Ocean. Some features of this genus can enhance opportunities for potential introgressive hybridization, e.g. sympatric distibution along the Brazilian coast, mixed known associations among species, karyotype uniformity and genome permeability. In this study we analyzed three genes of the mitochondrial genome to investigate the genetic diversity and occurrence of genetic mixture among eighty specimens of Stenella. All species exhibited moderate to high levels of genetic diversity (h = 0.833 to h = 1.000 and π = 0.006 to π = 0.015). Specimens of S. longirostris, S. attenuata and S. frontalis were clustered into differentiated haplogroups, in contrast, haplotypes of S. coeruleoalba and S. clymene were clustered together. We detected phylogenetic structure of mixed clades for S. clymene and S. coeruleoalba specimens, in the Southwest Atlantic Ocean, and also between S. frontalis and S. attenuata in the Northeast Atlantic Ocean, and between S. frontalis and S. longirostris in the Northwest Atlantic Ocean. These specimes were morphologically identified as one species but exhibited the maternal lineage of another species, by mitochondrial DNA. Our results demonstrate that ongoing gene flow is occurring among species of the genus Stenella reinforcing that this process could be one of the reasons for the confusing taxonomy and difficulties in elucidating phylogenetic relationships within this group.

Marine mammal strandings recorded in New Caledonia, South West Pacific Ocean, 1877 to 2022

“…The results highlighted here are consistent with those previously published on the genus Stenella (Faria et al 2022). For many species of Stenella, genetic diversity is high compared to other Delphinidae species (e.g.…”

Mitochondrial DNA diversity and genetic structure of striped dolphin Stenella coeruleoalba in the Northern Ionian Sea

“…The latter are indicated by red labels describing the mutated nucleotide position with respect to the first sequence in the dataset (Hap-1). et al 10.3389/fmars.2023.1088598 (driven by anthropogenic disruption of biological genetic patterns) representing a crucial point for the implementation of effective conservation measures (Faria et al, 2022). In effect, understanding anthropogenic hybridization dynamics can help identify effective and timely management actions for threatened species avoiding genomic extinction potentially led by the presence of admixed individuals and by human disturbances that cause hybridization (Santostasi et al, 2020).…”

Social and community structure of striped dolphins in a semienclosed Mediterranean embayment

“…Archer and Perrin (1999) hypothesized a polygynous mating system (one male mates with multiple females during a breeding season) for striped dolphins off Japan, but it is unknown whether striped dolphins in the Gulf of Corinth have a similar system. Regarding other species of the genus Stenella considered to be closely related to striped dolphins (Faria et al, 2022), Perrin and Mesnick (2003) concluded that the mating system of spinner dolphins in the eastern tropical Pacific varies geographically, from a more polygynous mating system in eastern spinner dolphins S. l. orientalis , to a more polygynandrous system in Gray's spinner dolphins S. l. longirostris , where sperm competition may play an important role. A study on spinner dolphin ecotypes by Andrews et al (2013) reported either a possible polygynous mating system (males being preferred by females based on their morphology), or a possible polygynandrous system (where male morphology does not drive sexual selection), depending on ecotype.…”