Genetic connectivity in allopatric seabirds: lack of inferred gene flow between Northern and Southern Buller’s albatross populations (Thalassarche bulleri ssp.)

ABSTRACT

The Buller’s albatross species complex is composed of two asynchronously breeding subspecies, the Northern Buller’s albatross (Thalassarche bulleri platei) and Southern Buller’s albatross (Thalassarche bulleri bulleri). The aim of this study was to test for genetic differentiation between Northern and Southern Buller’s albatross and to reassess genetic connectivity between these populations. Genotyping-by-Sequencing (GBS) was used to estimate gene flow and genome-wide divergence using 13 T. b. platei and 40 T. b. bulleri samples. The STACKS de novo and reference guided pipelines were used to call single nucleotide polymorphisms (SNPs) for three data sets: one each for Northern and Southern Buller’s and a third for both taxa together. The number of SNPs in each de novo data set was relatively consistent from 12,148 to 11,898 for Northern and Southern Buller’s albatross collections, respectively. A random subsample of 1000 SNPs from each of the two groups indicated that mean per-site nucleotide diversity and heterozygosity were slightly higher for Northern Buller’s albatross (π = 0.335; H_E = 0.322) than for either of the two Southern Buller’s albatross breeding colonies (π = 0.286 and 0.294; H_E = 0.275 and 0.288). Both STRUCTURE and discriminant analysis of principal components (DAPC) consistently showed differentiated clusters corresponding to Northern and Southern Buller’s but did not resolve population structure among Southern Buller’s breeding populations. These results indicate that an asynchronous breeding season likely limits gene flow between Northern and Southern Buller’s albatross and have important implications for the taxonomic status of Buller’s albatrosses.

KEYWORDS:

• Biodiversity
• conservation
• genetics
• phylogeography
• speciation
• management units

Acknowledgements

We thank Igor Debski, Katie Clemens-Seely (New Zealand’s Department of Conservation), Paul Sagar, Jean-Claude Stahl (National Institute of Water and Atmospheric Research Ltd.), Biz Bell (Wildlife Management International Ltd), Natalie Forsdick, Kate McKenzie, and the Conservation Services Programme for their assistance with sampling and support for this project and Shannon Clarke and others at AgResearch for their support with GBS library preparation and sequencing. Funding for this research was provided by the New Zealand Department of Conservation (contract 4656), and MBIE programme C10X1306 ‘Genomics for Production and Security in a Biological Economy’ to AgResearch. Geoff Chambers thanks VUW for alumnus scholar support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by the New Zealand Department of Conservation [contract 4656]; Ministry of Business, Innovation & Employment programme C10X1306 ‘Genomics for Production and Security in a Biological Economy’ to AgResearch.