Abstract
Due to their worldwide distribution and occupancy of different types of environments, bottlenose dolphins display considerable morphological variation. Despite limited understanding about the taxonomic identity of such forms and connectivity among them at global scale, coastal (or inshore) and offshore (or oceanic) ecotypes have been widely recognized in several ocean regions. In the Southwest Atlantic Ocean (SWA), however, there are scarce records of bottlenose dolphins differing in external morphology according to habitat preferences that resemble the coastal‐offshore pattern observed elsewhere. The main aim of this study was to analyze the genetic variability, and test for population structure between coastal (n = 127) and offshore (n = 45) bottlenose dolphins sampled in the SWA to assess whether their external morphological distinction is consistent with genetic differentiation. We used a combination of mtDNA control region sequences and microsatellite genotypes to infer population structure and levels of genetic diversity. Our results from both molecular marker types were congruent and revealed strong levels of structuring (microsatellites F ST = 0.385, p < .001; mtDNA F ST = 0.183, p < .001; ΦST = 0.385, p < .001) and much lower genetic diversity in the coastal than the offshore ecotype, supporting patterns found in previous studies elsewhere. Despite the opportunity for gene flow in potential “contact zones”, we found minimal current and historical connectivity between ecotypes, suggesting they are following discrete evolutionary trajectories. Based on our molecular findings, which seem to be consistent with morphological differentiations recently described for bottlenose dolphins in our study area, we recommend recognizing the offshore bottlenose dolphin ecotype as an additional Evolutionarily Significant Unit (ESU) in the SWA. Implications of these results for the conservation of bottlenose dolphins in SWA are also discussed.
Highlights
The intraspecific variation is critical for conservation biology because it addresses variability that is relevant for species persistence and evolutionary potential (e.g., Allendorf & Luikart, 2007)
Microsatellite genotypes and mtDNA sequences were identical in replicated samples, and no samples were identified as duplicates for the 48 new samples analyzed in this study
The final new dataset consisted of 25 males and 20 females for offshore samples and two males and one female for the three dolphins sampled along the coast of Bahía San Antonio (BSA) (Table 1)
Summary
The intraspecific variation is critical for conservation biology because it addresses variability that is relevant for species persistence and evolutionary potential (e.g., Allendorf & Luikart, 2007). The identification of distinct population segments, can be a challenging task This is especially true for highly mobile and widely distributed species inhabiting the marine environment that lacks evident physical barriers to gene flow (Hoelzel, 2009; Palumbi, 1994). The use of genetic markers has increased substantially in cetacean studies, revealing varying levels of populations structuring over large and small spatial scales for some species (e.g., Natoli et al, 2004; Pérez-Alvarez et al, 2017; Rosel, Hansen, & Hohn, 2009). The molecular approach, when integrated with phenotypic and ecological data, has proven to provide reliable information for cetacean taxonomic diagnosis and for understanding evolutionary forces shaping genetic divergence (e.g., Caballero et al, 2007; Cunha et al, 2015; Louis, Fontaine, et al, 2014; Wang, Chou, & White, 1999)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
