Raw sequencing data (3RAD) for the smooth hammerhead shark Sphyrna zygaena

Globally, hammerhead sharks have experienced severe declines owing to
continued overexploitation and anthropogenic change. The smooth hammerhead
shark Sphyrna zygaena remains understudied compared to other members of
the family Sphyrnidae. Despite  its Vulnerable status, a
comprehensive understanding of its genetic landscape remains lacking in
many regions worldwide. The present study aimed to conduct a fine-scale
genomic assessment of Sphyrna zygaena within the highly dynamic marine
environment of South Africa’s coastline, using thousands of single
nucleotide polymorphisms (SNPs) derived from restriction site-associated
DNA sequencing (3RAD). A combination of differentiation-based outlier
detection methods and genotype-environment association (GEA) analysis were
employed in Sphyrna zygaena. Subsequent assessments of putatively adaptive
loci revealed a distinctive south to east genetic cline. Amongst these,
notable correlations between adaptive variation and sea-surface dissolved
oxygen and salinity were evident. Conversely, analysis of 111,243 neutral
SNP markers revealed a lack of regional population differentiation, a
finding that remained consistent across various analytical approaches.
These results provide evidence for the presence of differential selection
pressures within a limited spatial range, despite high gene flow implied
by the selectively neutral dataset. This study offers notable insights
regarding the potential impacts of genomic variation in response to
fluctuating environmental conditions in the circumglobally distributed
Sphyrna zygaena.