Phylogeography reveals a panmictic population of the Chilean nylon shrimp along its exploitation range in the southeast Pacific Ocean

The nylon shrimp Heterocarpus reedi is the most important commercial demersal crustacean species along the central coast of Chile in the southeast Pacific, with an intense fishery since the 1950s. It inhabits between 155 and 800 m of depth and is harvested along most of its distributional range (21°S to 39°S) by bottom trawling. Current management policy considers a single population unit on the lower continental shelf margin and upper slope along the exploitation area. The goal of this study was to assess the genetic diversity and differentiation of H . reedi along the geographic area of exploitation, representing the first insights into population genetics of a demersal crustacean from Chile. We analyzed 446 partial sequences of the mitochondrial COI gene from individuals captured using bottom trawls from 14 sites separated by 1° of latitude, covering the exploitation area and bathymetric range of the benthic adults. Data showed high genetic diversity despite an extensive fishing pressure and absence of genetic differentiation among sites. Haplotype diversity showed a negative correlation with depth of the trawling, consistent with lower abundance of individuals at depths greater than 400 m. Also, a high effective population size and a post-LGM demographic expansion was detected. Lack of spatial and bathymetrical genetic differentiation and extensive gene flow reflect that the species is composed of a single panmictic unit. Phylogeographic structure suggests considering latitude, depth, and temporal variation in future assessments of the species.