Concordance between genetic diversity and marine biogeography in a highly mobile marine mammal, the Risso's dolphin

Abstract

Aim:The heterogeneity of the marine environment is thought to be the origin of marine biodiversity, often delineated in marine biogeographical provinces. Cetaceans are highly mobile aquatic mammals, but even those species inhabiting seemingly boundary-free open waters are found to exhibit degrees of population structure, often attributed to ecological and behavioural factors such as resource specialization and site fidelity. Our aim in this study is to test the hypothesis that a cosmopolitan, resource-specialist dolphin species, the Risso's dolphin (Grampus griseus) will show an association between genetic diversity and biogeographical provinces.Location: North Pacific and North Atlantic Oceans. Methods:We examined genetic variation at 19 microsatellite loci among 236 samples collected from a range of locations in the North Pacific Ocean, and for a 473 bp mitochondrial DNA control region sequence in 213 samples from the North Pacific and North Atlantic Oceans to assess genetic diversity, population structure and historic population dynamics. Results:We found differentiation in the North Pacific primarily among three populations corresponding to the marine biogeographical provinces of the Kuroshio-Oyashio Current (Sino-Japanese), California Current (California), and Eastern Tropical Pacific. Analyses using mitochondrial DNA data further reveal that these three populations are genetically different from the populations in the North Atlantic Ocean and Mediterranean Sea, without strong lineage sorting, and that the western North Pacific population experienced a period of population expansion while the Eastern Tropical Pacific population remained stable. Main conclusions:We find evidence for biogeographical endemism in a highly mobile marine mammal species that nevertheless shows evidence for long-range dispersion within and to a lesser extent among biogeographical provinces. We conclude that distinct ecological processes promote differentiation, even though this species forages on narrow range of prey species.

Oceanographic barriers, divergence, and admixture: Phylogeography and taxonomy of two putative subspecies of short‐finned pilot whale

“…The Eastern Pacific Barrier is a known barrier to many shallow, coastally‐distributed fishes, corals, and other invertebrates (Bowen et al, ; Chow et al, ; Rocha et al, ). Increasing evidence suggests it may also be an important barrier separating mobile trans‐Pacific or globally‐distributed species, such as Galapagos sharks ( Carcharhinus galapagensis ) (Pazmiño et al, ), tope sharks ( Galeorhinus galeus ) (Chabot, ), Risso's dolphins ( Grampus griseus ) (Chen et al, ), and spinner dolphins ( Stenella longirostris ) (Leslie & Morin, ). Some evidence suggests that the barrier may be semi‐permeable to some species (Lessios & Robertson, ), allowing occasional migration and mixing between the eastern and western Pacific Ocean.…”

Genomic signatures of divergent selection are associated with social behaviour for spinner dolphin ecotypes

“…Minimal population genetic structure across the ETP has been found for other cetacean species (e.g., Chen et al, 2018 ;Leslie & Morin, 2016 ;Van Cise et al, 2016 ) and pelagic fishes (e.g., Cardeñosa et al, 2014 ;Mamoozadeh et al, 2020 ). For the spotted dolphin, which has a similar distribution as spinner dolphins in the ETP and sometimes schools together with this species, GBS data (3721 SNPs) identified weak but significant genetic divergence between two offshore ETP populations ( F ST = 0.0019), and moderate divergence between the offshore populations vs a coastal population ( F ST = 0.0416 and 0.0734) (Leslie & Morin, 2016 ).…”

Population genetic diversity and historical dynamics of Fraser’s dolphins Lagenodelphis hosei

“…There is evidence for population expansions during the early Holocene for a number of cetacean species (e.g. Banguera-Hinestroza et al 2014;Louis et al 2014;Moura et al 2014;Chen et al 2017Chen et al , 2018. Furthermore, there are clues suggesting range expansion for Fraser's dolphin populations in the modern age.…”