Meeting Abstract

37.6  Tuesday, Jan. 5  Demographic history and ecological connectivity of the scalloped hammerhead shark, Sphyrna lewini, in the Eastern Pacific NANCE, Holly/A*; MARKO, Peter/B; Clemson University; Clemson University hnance@clemson.edu

Describing basic migration rates and patterns of large, marine predators is challenging, yet necessary for species that are overfished and at risk of extinction. To that end, we have used molecular data to characterize the population genetic structure of the globally endangered (IUCN Red List) Sphyrna lewini and to infer levels of connectivity, demography, and divergence throughout the Eastern Pacific (EP) range of this globally distributed shark. Using 15 microsatellite loci from nearly 400 sharks sampled at eight sites between Mexico and Ecuador, we found significant genetic differentiation with a global F_ST of 0.005 (P < 0.001), and significant values for most pairwise comparisons. We did not detect significant structure at a 548 bp region of mtDNA control region, though this was probably due to very low diversity. Coalescent-based analyses indicated that each EP site we sampled was comprised of a genetically distinct population with low ecological connectivity. Despite this current genetic structure in the EP, the populations we sampled shared a common demographic history: mtDNA showed evidence of a population expansion roughly 230,000 years ago. Divergence genetics analyses based on both mtDNA and microsatellite loci showed that population divergence times were very recent (averaging only 540 years ago), and that effective sizes of all extant populations were several orders of magnitude smaller than ancestral population sizes. Overall, our results point to a relatively recent fragmentation of S. lewini populations throughout the EP, potentially driven by recent population declines.