Genomics Scale Analysis of Population Structure, Genetic Diversity, and Effective Population Size in the Critically Endangered Angelshark (Squatina squatina)

Author

• Justin Chandler-Holtz, Nova Southeastern UniversityFollow

Defense Date

8-4-2026

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Biological Sciences

First Advisor

Mahmood Shivji, Ph.D.

Second Advisor

Andrea Bernard, Ph.D.

Third Advisor

John Swenson, Ph.D.

Keywords

Multiple paternity, Single Nucleotide Polymorphism, Canary Islands, Heterozygosity, Private alleles

Abstract

The angelshark, Squatina squatina, a Critically Endangered species, has its last apparent stronghold of abundance around the Canary Islands.  Although now protected, the species’ long-term resilience hinges on population genetic traits, including genetic diversity, a key influence on adaptability to environmental changes.  Using high-resolution, genome-wide single nucleotide polymorphisms (SNPs), I assessed the genetic status of S. squatina in the Canary Islands.  The SNP markers revealed the islands of Gran Canaria, Tenerife, and Lanzarote each harbor a genetically distinct population.  Mean genomic autosomal heterozygosity (0.000253) in each S. squatina population was lower than those of all other shark species and populations assessed to date, signaling possibly constrained capacity for future adaptive potential. Notably, however, inbreeding levels were low across all populations (mean F = 0.0103), implying inbreeding depression is not the cause of the low genetic diversity.  Effective population size (N_e) estimates of the S. squatina population at Gran Canaria included point estimates over 1,000 and Jackknife 95% lower confidence intervals above 500, suggesting resilience against further genetic diversity loss in the foreseeable future.  The N_e estimates for Lanzarote and Tenerife islands possessed comparatively lower confidence intervals with minimum N_e estimates of over 100, indicating resilience to genetic diversity loss over at least the next five generations in both populations.  Overall, my results suggest that despite the notably low current genetic diversity of S. squatina, future genetic diversity loss in this species at the Canary Islands may be preventable with continuation and enhancement of current conservation efforts.

NSUWorks Citation

Justin Chandler-Holtz. 2026. Genomics Scale Analysis of Population Structure, Genetic Diversity, and Effective Population Size in the Critically Endangered Angelshark (Squatina squatina). Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (246)
https://nsuworks.nova.edu/hcas_etd_all/246.