| dc.description.abstract | Overharvesting has been implicated in altering the population structure of marine
organisms, reducing genetic diversity and adaptive capacity. Overharvested fisheries can
be particularly vulnerable to environmental and anthropogenic stressors due to the loss of
advantageous mutations. The Hawaiian broadcast-spawning limpet, Cellana exarata, is
subject to varying levels of harvesting pressure on different islands, ranging from no
harvest on the uninhabited island of Nihoa in the Papahānaumokuākea Marine National
Monument, to a reduction in population density on Maui and Kaua‘i, to near extirpation
on O‘ahu, the most populous of the Hawaiian Islands. In this study, we use genome-wide
surveys of genetic variation (ezRAD, >21,000 loci) on C. exarata from the islands of
Nihoa, Kaua‘i, Maui, O‘ahu, and Hawai‘i to test for relationships between genetic
diversity, population size, island age, and harvest pressure. Global estimates of genetic
differentiation among islands are greater than those estimated with mtDNA. Pairwise
comparisons among islands indicate a substantial difference in genetic composition
between the inhabited Main Hawaiian Islands and the uninhabited island, Nihoa.
Estimates of nucleotide diversity (π) were greatest on Nihoa (π = 2.05 × 10−3), despite
having the smallest estimated population size (without harvesting); estimates of
nucleotide diversity on the Big Island of Hawai’i are the lowest of all the islands in this
study (π = 1.71 × 10−3), despite having the largest estimated population size. This
difference in genetic diversity, while initially counter intuitive, is correlated with island
age and indicates that C. exarata populations within the MHI experienced a recent
bottleneck. Overall, these results suggest that the PMNM harbors a stockpile of genetic
diversity for C. exarata, despite relatively small population sizes when compared to the
MHI. | en |
