Assessing differences among elasmobranch nurseries to aid conservation based on a genomics framework

Area of Science:

• Marine Biology
• Conservation Genetics
• Population Genomics

Background:

• Elasmobranch nurseries vary significantly in environmental conditions, demographics, and usage patterns.
• These variations impact genetic diversity distribution among nurseries.
• Current conservation strategies often overlook these nursery-specific differences due to characterization difficulties.

Purpose of the Study:

• To assess differences in connectivity, genetic variation, and breeder numbers among scalloped hammerhead (Sphyrna lewini) nurseries.
• To analyze genetic structure and dispersal patterns within and between western North Atlantic nurseries.
• To apply a genomic framework for conservation assessments of elasmobranch nurseries.

Main Methods:

• Genotyped 472 young scalloped hammerheads using a reduced-representation genomic approach (8,334 SNP loci).
• Inferred full- and half-sibling relationships.
• Utilized mitochondrial genome haplotypes to distinguish maternally and paternally related half-siblings.

Main Results:

• Identified 45 sibling pairs, with 91% originating from the same nursery, indicating strong site fidelity.
• Detected weak but significant genetic heterogeneity among nurseries (0.02% variation, FST = 0.00018).
• Observed differences in standing genetic variation and effective population size, though not statistically significant.

Conclusions:

• Female scalloped hammerheads demonstrate consistent use of specific nurseries.
• Connectivity between nurseries, facilitated by straying individuals, aids in the dispersal of genetic variation.
• This dispersal enhances population resilience to environmental changes, highlighting the importance of understanding nursery connectivity for conservation.