Postglacial Colonization of Northern Coastal Habitat by Bottlenose Dolphins: A Marine Leading-Edge Expansion?

Oscillations in the Earth’s temperature and the subsequent retreating and advancing of ice-sheets around the polar regions are thought to have played an important role in shaping the distribution and genetic structuring of contemporary high-latitude populations. After the Last Glacial Maximum (LGM), retreating of the ice-sheets would have enabled early colonizers to rapidly occupy suitable niches to the exclusion of other conspecifics, thereby reducing genetic diversity at the leading-edge. Bottlenose dolphins (genus Tursiops) form distinct coastal and pelagic ecotypes, with finer-scale genetic structuring observed within each ecotype. We reconstruct the postglacial colonization of the Northeast Atlantic (NEA) by bottlenose dolphins using habitat modeling and phylogenetics. The AquaMaps model hindcasted suitable habitat for the LGM in the Atlantic lower latitude waters and parts of the Mediterranean Sea. The time-calibrated phylogeny, constructed with 86 complete mitochondrial genomes including 30 generated for this study and created using a multispecies coalescent model, suggests that the expansion to the available coastal habitat in the NEA happened via founder events starting ~15 000 years ago (95% highest posterior density interval: 4 900–26 400). The founders of the 2 distinct coastal NEA populations comprised as few as 2 maternal lineages that originated from the pelagic population. The low effective population size and genetic diversity estimated for the shared ancestral coastal population subsequent to divergence from the pelagic source population are consistent with leading-edge expansion. These findings highlight the legacy of the Late Pleistocene glacial cycles on the genetic structuring and diversity of contemporary populations

One Species or Two? Vicariance, Lineage Divergence and Low mtDNA Diversity in Geographically Isolated Populations of South Asian River Dolphin

Despite their endangered status, the taxonomic relationship between the two geographically isolated South Asian river dolphin populations has never been comprehensively assessed and remains contentious. Here we present the first dedicated evaluation of the molecular phylogenetic relationship between the Indus (Platanista gangetica minor) and Ganges (Platanista gangetica gangetica) River dolphins using mitochondrial DNA from the control region and cytochrome b, extracted from museum specimens. The 458 bp partial control region sequences from 26 Indus River dolphin samples exhibited no variation. Only six haplotypes were identified in the 31 (18 Indus; 13 Ganges) complete (856 bp) control region sequences obtained, none were shared between subspecies, and there were five fixed differences between them. Similarly low genetic diversity was found in a 541 bp section of the cytochrome b gene (n = 29). The lack of shared haplotypes and fixed differences resulted in ΦST for the partial control region sequences of 0.932 (p < 0.0001) and FST of 0.843 (p < 0.0001), indicating the long-term absence of gene flow and clear genetic differentiation between the two geographically isolated populations. An externally calibrated molecular clock estimated that Indus and Ganges dolphins diverged around 550,000 years ago (95 % posterior probability 0.13-1.05 million years ago), possibly when dolphins from the Ganges dispersed into the Indus during drainage capture. © 2014 Springer Science+Business Media New York

One Species or Two? Vicariance, Lineage Divergence and Low mtDNA Diversity in Geographically Isolated Populations of South Asian River Dolphin

Despite their endangered status, the taxonomic relationship between the two geographically isolated South Asian river dolphin populations has never been comprehensively assessed and remains contentious. Here we present the first dedicated evaluation of the molecular phylogenetic relationship between the Indus (Platanista gangetica minor) and Ganges (Platanista gangetica gangetica) River dolphins using mitochondrial DNA from the control region and cytochrome b, extracted from museum specimens. The 458 bp partial control region sequences from 26 Indus River dolphin samples exhibited no variation. Only six haplotypes were identified in the 31 (18 Indus; 13 Ganges) complete (856 bp) control region sequences obtained, none were shared between subspecies, and there were five fixed differences between them. Similarly low genetic diversity was found in a 541 bp section of the cytochrome b gene (n = 29). The lack of shared haplotypes and fixed differences resulted in ΦST for the partial control region sequences of 0.932 (p < 0.0001) and FST of 0.843 (p < 0.0001), indicating the long-term absence of gene flow and clear genetic differentiation between the two geographically isolated populations. An externally calibrated molecular clock estimated that Indus and Ganges dolphins diverged around 550,000 years ago (95 % posterior probability 0.13-1.05 million years ago), possibly when dolphins from the Ganges dispersed into the Indus during drainage capture. © 2014 Springer Science+Business Media New York

One species or two? Vicariance, lineage divergence and low mtDNA diversity in geographically isolated populations of South Asian river dolphin

Despite their endangered status, the taxonomic relationship between the two geographically isolated South Asian river dolphin populations has never been comprehensively assessed and remains contentious. Here we present the first dedicated evaluation of the molecular phylogenetic relationship between the Indus (Platanista gangetica minor) and Ganges (Platanista gangetica gangetica) River dolphins using mitochondrial DNA from the control region and cytochrome b, extracted from museum specimens. The 458 bp partial control region sequences from 26 Indus River dolphin samples exhibited no variation. Only six haplotypes were identified in the 31 (18 Indus; 13 Ganges) complete (856 bp) control region sequences obtained, none were shared between subspecies, and there were five fixed differences between them. Similarly low genetic diversity was found in a 541 bp section of the cytochrome b gene (n = 29). The lack of shared haplotypes and fixed differences resulted in ΦST for the partial control region sequences of 0.932 (p &lt; 0.0001) and FST of 0.843 (p  &lt; 0.0001), indicating the long-term absence of gene flow and clear genetic differentiation between the two geographically isolated populations. An externally calibrated molecular clock estimated that Indus and Ganges dolphins diverged around 550,000 years ago (95 % posterior probability 0.13–1.05 million years ago), possibly when dolphins from the Ganges dispersed into the Indus during drainage capture

Genetics and stable isotopes reveal non-obvious population structure of bottlenose dolphins (Tursiops truncatus) around the Balearic Islands

The effective management of wildlife requires that populations are defined in a biological sensible manner. We investigated the population structure of bottlenose dolphins (Tursiops truncatus) in waters around the Balearic archipelago using two complementary techniques; DNA markers (i.e. microsatellites and a portion of the mitochondrial control region) and stable isotopes (δ13C, δ15N). We used tissue samples from biopsies (n = 50) and fresh carcasses (n = 7) obtained around the islands of Gimnèsies and Pitiüses, and Comunitat Valenciana (Western Mediterranean Sea). Genetic differentiation between individuals from Gimnésies and Pitiüses and between individuals from across these two areas and individuals from Comunitat Valenciana was significant when assessing FST, but no substructure was found using clustering methods (i.e. DAPC and Bayesian clustering). δ13C and δ15N profiles were not significantly different between dolphins from Gimnésies and Pitiüses. Dolphins from both areas showed coastal carbon isotopic values and similar trophic niche levels. However, the trophic niche of dolphins from Gimnésies was broader than the trophic niche of Pitiüses’ dolphins. These results indicate non-obvious population structure between the mainland and the archipelago, or between islands within the archipelago. The use of combined techniques, which integrate information over different time scales, is applicable to other species and areas