Phylogeography of the Pacific Angel Shark (Squatina californica) in the Eastern Pacific

Abstract

Squatina californica is a near-threatened angel shark distributed in coastal areas of eastern Pacific. Despite its wide distribution and the conservation threats, basic knowledge of the species populations, evolutionary history and genetic diversity is scarce. In this study, we use two mitochondrial genetic markers (Control Region of mtDNA and Cytochrome C Oxidase subunit I) to explore the species' phylogeography. We included samples from locations in the Southern Californian Pacific (SCP), the Gulf of California (GC) and the Southeast Pacific (SEP). We identified three populations of the Pacific Angel Shark, corresponding to the regions SCP, GC and SEP. These results show an antitropical distribution for the species, which may be a consequence of the climatic instability of Central America during the Pliocene. Additionally, we infer that the divergence of the SCP populations from those of the GC coincided closely with the formation of the Baja California Peninsula, without current migration through the southern end of the peninsula. Finally, we detected a signal of population expansion and substructure within the GC, probably promoted by environmental heterogeneity in this area. Our results indicate that the three populations identified herein should be considered separate management units, because they exhibited independent evolutionary histories that may influence their levels of resilience to fishing pressure.