Genetic diversity and demographic history of Dosidicus gigas (Cephalopoda: Ommastrephidae) in the Humboldt Current System

Abstract

During the late Pleistocene-Holocene, the Humboldt Current System (HCS, Peru-Chile) was subject to important oceanographic variations that may have affected the abundance and distri- bution of marine populations, as well as their genetic structure and diversity. The fast growth and short life span of jumbo squid Dosidicus gigas make this squid a valuable model organism for evalu- ating how environmental fluctuations affect the genetic diversity of marine populations. We sequenced a 657 bp fragment of the mtDNA cytochrome c oxidase I (COI) gene of 169 jumbo squids from 6 locations in the HCS. We measured and compared genetic diversity among localities and per- formed neutrality tests to detect deviation from mutation-drift equilibrium. We inferred the demo- graphic history of jumbo squids using Bayesian skyline analyses to estimate effective population size through time. A total of 23 haplotypes were found among the sequences. Haplotype and nucleotide diversity were low in all locations. D. gigas was characterized by an absence of population genetic structure and a star-like haplotype network. Neutrality test values were negative and statistically sig- nificant, and therefore consistent with a past population expansion. Similarly, Bayesian skyline analyses indicated a recent demographic expansion after the last glacial maximum. Our results suggest that D. gigas consists of a single, large population in the HCS, that may have experienced a dramatic demographic popu lation expansion consistent with the oceanographic changes associated with the last glacial- interglacial transition.