Genetic differentiation between humpback whales (Megaptera novaeangliae) from Atlantic and Pacific breeding grounds of South America

Abstract

Humpback whales wintering in tropical waters along the Atlantic and Pacific coasts of the South American continent are thought to represent distinct populations or “stocks.” Here we present the first analysis of genetic differentiation and estimates of gene flow between these breeding stocks, based on both mitochondrial DNA (mtDNA) control region sequences (465 bp) and 16 microsatellite loci from samples collected off Brazil (n = 277) and Colombia (n = 148), as well as feeding areas near the western Antarctic Peninsula (n = 86). We found significant differentiation between Brazilian and Colombian breeding grounds at both mtDNA (FST = 0.058) and microsatellite (FST = 0.011) markers and corroborated previous studies showing genetic similarity between humpbacks from Colombia and those from Antarctic Peninsula feeding areas. Estimates of long‐term gene flow between Brazil and Colombia were low to moderate, asymmetrical, and mostly mediated by males. Assignment procedures detected some cases of interchange and individuals of admixed ancestry between breeding grounds, indicating limited mixing of individuals between these stocks. Overall, results highlight the differentiation of humpback whale breeding populations with adjacent feeding grounds. This appears to be a remarkable example of fidelity to seasonal habitat in the absence of any contemporary barriers.

Effective population size and the genetic consequences of commercial whaling on the humpback whales (Megaptera novaeangliae) from Southwestern Atlantic Ocean

“…This high genetic diversity is in agreement with other breeding grounds studied in the Southern Hemisphere for both nuclear and mitochondrial markers (e.g. Valsecchi et al , 2002 ; Garrigue et al , 2004 ; Pomilla and Rosenbaum, 2006 ; Olavarría et al , 2007 ; Rosenbaum et al , 2009 ; Cypriano-Souza et al , 2017 ). Nevertheless, in the Southwestern Atlantic population, as well as most other humpback populations, severe reductions of their historical size by commercial whaling are well documented.…”

“…Our extended sampling confirms our previous results on the high nuclear DNA diversity of the humpback whale population that winters off the Brazilian coast (BSA), which is also compatible with its high mtDNA variability ( Engel et al , 2008 ; Cypriano-Souza et al , 2010 , 2017 ). This high genetic diversity is in agreement with other breeding grounds studied in the Southern Hemisphere for both nuclear and mitochondrial markers (e.g.…”

“…However, a recent study indicates that single-sample estimators of contemporary N e based on linkage disequilibrium were not affected significantly with migration rates up to approximately 5–10% ( Waples and England, 2011 ). Indeed, the migration rates between the Atlantic and Pacific breeding grounds of South America were estimated to be lower than the above limits ( Cypriano-Souza et al , 2017 ). Likewise, low migration rates based on mtDNA data have been estimated between humpbacks from Brazil and from breeding grounds in the Southeastern Atlantic Ocean (H.C. Rosenbaum, personal communication).…”

Assessing the recovery of an Antarctic predator from historical exploitation

“…A recent study on population structure reported a total of 54 distinct mtDNA haplotypes for WSA humpbacks [68], with only five of those being unique to the WSA population (i.e. not reported elsewhere in the Southern Hemisphere).…”

Ancient female philopatry, asymmetric male gene flow, and synchronous population expansion support the influence of climatic oscillations on the evolution of South American sea lion (Otaria flavescens)

“…the European eel, Anguilla Anguilla [ 1 ]; the blue hake, Antimora rostrata [ 2 ]; and the common dolphin, Delphinus delphis in the North Atlantic [ 3 ]), it is more common for population subdivision to be found. This is especially true for cetacean species, sometimes over relatively smaller geographic scales [ 4 ] and the challenge is to understand the relevant processes. In some cases, the boundaries to gene flow appear to be associated with habitat or resource specializations [ 5 ].…”