Major Histocompatibility Complex (MHC) class II sequence polymorphism in long-finned pilot whale (Globicephala melas) from the North Atlantic

ABSTRACT

Determining how intra-specific genetic diversity is apportioned among natural populations is essential for detecting local adaptation and identifying populations with inherently low levels of extant diversity which may become a conservation concern. Sequence polymorphism at two adaptive loci (MHC DRA and DQB) was investigated in long-finned pilot whales (Globicephala melas) from four regions in the North Atlantic and compared with previous data from New Zealand (South Pacific). Three alleles were resolved at each locus, with trans-species allele sharing and higher levels of non-synonymous to synonymous substitution, especially in the DQB locus. Overall nucleotide diversities of 0.49 ± 0.38% and 4.60 ± 2.39% were identified for the DRA and DQB loci, respectively, which are relatively low for MHC loci in the North Atlantic, but comparable to levels previously described in New Zealand (South Pacific). There were significant differences in allele frequencies within the North Atlantic and between the North Atlantic and New Zealand. Patterns of diversity and divergence are consistent with the long-term effects of balancing selection operating on the MHC loci, potentially mediated through the effects of host-parasite coevolution. Differences in allele frequency may reflect variation in pathogen communities, coupled with the effects of differential drift and gene flow.

RESPONSIBLE EDITOR:

• Rus Hoelzel

KEYWORDS:

• Adaptive markers
• Cetacea
• evolution

Acknowledgements

Samples were collected under the auspices of strandings monitoring programmes run by the Sociedade Portuguesa de Vida Selvagem, Coordinadora para o Estudio dos Mamíferos Mariños (supported by the regional government Xunta de Galicia), the Scottish Agriculture College Veterinary Science Division, the UK Cetacean Strandings Investigation Programme (jointly funded by Defra and the Devolved Governments of Scotland and Wales), the Museum of Natural History of the Faroe Islands and the Marine Mammal Rescue & Research Program of the International Fund for Animal Welfare. We thank all the members of those institutions for their assistance with data and sample collection. Published in collaboration between Universidade do Minho and the University of Aberdeen.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Sílvia S. Monteiro http://orcid.org/0000-0002-8784-7276

Additional information

Funding

Silvia S. Monteiro and Marisa Ferreira were supported by a PhD grant from the Fundação para a Ciência e Tecnologia (ref. SFRH/BD/38735/2007 and SFRH/BD/30240/2006, respectively). Alfredo López was supported by a postdoctoral grant from the Fundação para a Ciência e Tecnologia (ref. SFRH/BPD/82407/2011). Catarina Eira is supported by CESAM (UID/AMB/50017), from FCT/MEC through national funds and FEDER (PT2020, Compete 2020). The work related with strandings and tissue collection in Portugal was partially supported by the SafeSea Project EEAGrants PT 0039 (supported by Iceland, Liechtenstein and Norway through the EEA Financial Mechanism), by the Project MarPro–Life09 NAT/PT/000038 (funded by the European Union–Program Life+) and by the project CetSenti FCT RECI/AAG-GLO/0470/2012; FCOMP-01-0124-FEDER-027472 (funded by the Program COMPETE and Fundação para a Ciência e Tecnologia).