Are the “Bastards” coming back? Molecular identification of live blue and fin whale hybrids in the North Atlantic Ocean

 

Martine Berube, Tom Oosting, Alex Aguilar, Simon Berrow, Pauline Gauffier, Wensi Hao, Mads Peter Heide-Jørgensen, Kit M. Kovacs, Scott Landry, Finn Larsen, Christian Lydersen, Vidal Martin, Nils Øien, Simone Panigada, Rui Prieto, Christian Ramp, Jooke Robbins. Conor Ryan, Richard Sears, Monica Silva, Gisli Vikingsson, Per J. Palsbøll

 

Abstract:


Hybridization among cetaceans is rarely reported in the wild, which may be due to the difficulty of identifying and locating hybrids, or reduced hybrid viability. However, blue x fin whale hybrids have been suggested since 1887, when Cocks reported more than six alleged hybrids, labeled “Bastards”, along the Lapland coast. Since then, four blue x fin whale individuals were identified during whaling operations in Iceland and Spain providing the first genetic evidence of mysticete hybridization. Extensive non-lethal collections of skin biopsy samples started since the early 1990s in several ocean basins should enable detection of additional hybrids. Indeed, in 1998, an individual from Iceland which shared characteristics of both fin and blue whales was sighted and later molecular analyses confirmed the animal as a fin x blue whale hybrid. During large-scale routine genotyping of blue and fin whale samples we identified additional specimens with microsatellite alleles that are rare in the designated species. More detailed analyses of those specimens, specifically DNA sequencing of two nuclear markers, the a-lactalbumin and the Butyrophilin gene, confirmed the presence of two additional, live fin x blue hybrids from the North Atlantic; one individual sampled in the Gulf of St. Lawrence, Canada; and another in the Azores (Portugal). The Gulf of St. Lawrence hybrid was re-sighted in 2012. The presence of blue x fin whales hybrids both during early and after commercial whaling suggests the possibility that blue x fin hybrids are not necessarily due to lack of con-specific mate choice among blue whales after whaling, but may be a “natural” recurrent phenomenon. The evolutionary implications of these hybrids are unclear, but appear not to have degraded the taxonomic integrity of fin or blue whales.