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Mixing of porpoise ecotypes in southwestern UK waters revealed by genetic profiling

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ABSTRACT

Contact zones between ecotypes are windows for understanding how species may react to climate changes. Here, we analysed the fine-scale genetic and morphological variation in harbour porpoises (Phocoena phocoena) around the UK by genotyping 591 stranded animals at nine microsatellite loci. The data were integrated with a prior study to map at high resolution the contact zone between two previously identified ecotypes meeting in the northern Bay of Biscay. Clustering and spatial analyses revealed that UK porpoises are derived from two genetic pools with porpoises from the southwestern UK being genetically differentiated, and having larger body sizes compared to those of other UK areas. Southwestern UK porpoises showed admixed ancestry between southern and northern ecotypes with a contact zone extending from the northern Bay of Biscay to the Celtic Sea and Channel. Around the UK, ancestry blends from one genetic group to the other along a southwest--northeast axis, correlating with body size variation, consistent with previously reported morphological differences between the two ecotypes. We also detected isolation by distance among juveniles but not in adults, suggesting that stranded juveniles display reduced intergenerational dispersal. The fine-scale structure of this admixture zone raises the question of how it will respond to future climate change and provides a reference point for further study.

No MeSH data available.


Related in: MedlinePlus

Geographical locations of the harbour porpoises sampling based on GPS coordinates or reported discovery location. (a) Global overview of the individuals considered in this study including the genotyped individuals from UK waters (red points) and the Northeast Atlantic individuals from Fontaine et al. [4] (yellow dots). (b) Locations of the UK samples have been subdivided into six regions around the UK and colour-coded accordingly for regional analyses.
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RSOS160992F1: Geographical locations of the harbour porpoises sampling based on GPS coordinates or reported discovery location. (a) Global overview of the individuals considered in this study including the genotyped individuals from UK waters (red points) and the Northeast Atlantic individuals from Fontaine et al. [4] (yellow dots). (b) Locations of the UK samples have been subdivided into six regions around the UK and colour-coded accordingly for regional analyses.

Mentions: In this study, we analysed the genetic structure of harbour porpoises around the UK using a dense sampling of 591 stranded animals (figure 1; electronic supplementary material , figures S1–S3) spanning a decade from 1990 to 2002 (electronic supplementary material, figure S4). We placed this ‘local’ genetic assessment within the global genetic structure of the harbour porpoises in the Northeast Atlantic by combining the UK dataset with previous data from Fontaine et al. [4]. We tested whether animals stranded around the UK show any evidence of mixed genetic ancestry from distinct genetic pools and morphological differentiation in terms of relative body size. Given the proximity of the Biscay admixture zone [4,18,20,31], porpoises in the southwestern part of the UK might be expected to show evidence of such mixed ancestry and could have larger body sizes, closer to Iberian porpoises. We also showed previously that gene flow and individual dispersal was restricted in space on the continental shelf north of the Bay of Biscay [4], creating a pattern of isolation by distance (IBD) [32,33]. Here, we tested whether such IBD exists around the UK and whether it differed between sex and age classes. Understanding the physical and ecological factors which influence the distribution of different ecotypes is central to understanding how this key pelagic predator may react to future climate change, and its subsequent impacts on Northeast Atlantic ecosystem [34].Figure 1.


Mixing of porpoise ecotypes in southwestern UK waters revealed by genetic profiling
Geographical locations of the harbour porpoises sampling based on GPS coordinates or reported discovery location. (a) Global overview of the individuals considered in this study including the genotyped individuals from UK waters (red points) and the Northeast Atlantic individuals from Fontaine et al. [4] (yellow dots). (b) Locations of the UK samples have been subdivided into six regions around the UK and colour-coded accordingly for regional analyses.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5383846&req=5

RSOS160992F1: Geographical locations of the harbour porpoises sampling based on GPS coordinates or reported discovery location. (a) Global overview of the individuals considered in this study including the genotyped individuals from UK waters (red points) and the Northeast Atlantic individuals from Fontaine et al. [4] (yellow dots). (b) Locations of the UK samples have been subdivided into six regions around the UK and colour-coded accordingly for regional analyses.
Mentions: In this study, we analysed the genetic structure of harbour porpoises around the UK using a dense sampling of 591 stranded animals (figure 1; electronic supplementary material , figures S1–S3) spanning a decade from 1990 to 2002 (electronic supplementary material, figure S4). We placed this ‘local’ genetic assessment within the global genetic structure of the harbour porpoises in the Northeast Atlantic by combining the UK dataset with previous data from Fontaine et al. [4]. We tested whether animals stranded around the UK show any evidence of mixed genetic ancestry from distinct genetic pools and morphological differentiation in terms of relative body size. Given the proximity of the Biscay admixture zone [4,18,20,31], porpoises in the southwestern part of the UK might be expected to show evidence of such mixed ancestry and could have larger body sizes, closer to Iberian porpoises. We also showed previously that gene flow and individual dispersal was restricted in space on the continental shelf north of the Bay of Biscay [4], creating a pattern of isolation by distance (IBD) [32,33]. Here, we tested whether such IBD exists around the UK and whether it differed between sex and age classes. Understanding the physical and ecological factors which influence the distribution of different ecotypes is central to understanding how this key pelagic predator may react to future climate change, and its subsequent impacts on Northeast Atlantic ecosystem [34].Figure 1.

View Article: PubMed Central - PubMed

ABSTRACT

Contact zones between ecotypes are windows for understanding how species may react to climate changes. Here, we analysed the fine-scale genetic and morphological variation in harbour porpoises (Phocoena phocoena) around the UK by genotyping 591 stranded animals at nine microsatellite loci. The data were integrated with a prior study to map at high resolution the contact zone between two previously identified ecotypes meeting in the northern Bay of Biscay. Clustering and spatial analyses revealed that UK porpoises are derived from two genetic pools with porpoises from the southwestern UK being genetically differentiated, and having larger body sizes compared to those of other UK areas. Southwestern UK porpoises showed admixed ancestry between southern and northern ecotypes with a contact zone extending from the northern Bay of Biscay to the Celtic Sea and Channel. Around the UK, ancestry blends from one genetic group to the other along a southwest--northeast axis, correlating with body size variation, consistent with previously reported morphological differences between the two ecotypes. We also detected isolation by distance among juveniles but not in adults, suggesting that stranded juveniles display reduced intergenerational dispersal. The fine-scale structure of this admixture zone raises the question of how it will respond to future climate change and provides a reference point for further study.

No MeSH data available.


Related in: MedlinePlus