Reconstruction of larval origins based on genetic relatedness and biophysical modeling

I Segura-García,J Hunt,M Tringali,L M Chérubin,S J Box,T Matthews,L Garavelli

doi:10.1038/s41598-019-43435-9

Abstract

The assessment of the mechanisms and patterns of larval connectivity between geographically separated populations leads to a better understanding of benthic marine population dynamics, especially in commercially valuable species. This study investigated for the first time the fine-scale temporal genetic variability of new settlers and their origins in a benthic marine organism with one of the longest pelagic larval phases, the Caribbean spiny lobster (Panulirus argus). We genotyped newly settled postlarvae in the Florida Keys and adults of spiny lobster from the Florida Keys and throughout the Caribbean Sea. We identified strong larval connectivity between Dominican Republic, Belize, Nicaragua, the Florida Keys, and West-Florida. The larval dispersal modeling suggests that Florida’s lobster population could receive recruits from within and from other areas outside its state and national maritime boundaries. The genetic analyses refine the oceanographic model indicating that the connectivity patterns described could also result from unknown parental populations sourcing adults and postlarvae in different spawning seasons to the Florida Keys. We discuss the importance of small temporal scales to identify patterns in larval export. Our findings are significant on two levels. From the larval dispersal perspective, genetic results and biophysical modeling identify patterns of gene flow enhancing persistence of local populations. From an economic and fishery perspective, P. argus is the most important commercial species in the Caribbean and our results inform how considering larval source and sink dynamics across international boundaries could improve management plans at local, national, and regional levels.

Highlights

The increasing number of fisheries categorized as fully or overexploited[1,2] demonstrates the need to more fully understand population dynamics of key fisheries to prevent or reverse stock decline and collapse
The direct genetic comparison between adults and recruits has yet to be investigated. We used both indirect and direct genetic methods to investigate the fine-scale temporal variation in larval connectivity and recruitment by estimating the extent of relatedness between postlarvae settled in the Florida Keys and adult spiny lobsters from geographically remote populations across the Caribbean Sea
All loci were retained for further analyses given the high relatedness resolving power estimated by the polymorphic information content (PIC), (Table S1)

Summary

Introduction

The increasing number of fisheries categorized as fully or overexploited[1,2] demonstrates the need to more fully understand population dynamics of key fisheries to prevent or reverse stock decline and collapse. In P. argus, the predicted average distance a larva settles from its release location is reduced by over 60% when larval diel vertical migration is incorporated into a biophysical transport model[10] Another factor affecting the assessment of larval dispersal is the effect of climate change; in the European lobster, Homarus gammarus, the increase of water temperature is expected to increase temperature-dependent mortality of larvae, as a result of a forward shift in hatching and poor quality and abundance of food[18]. We used both indirect and direct genetic methods to investigate the fine-scale temporal variation in larval connectivity and recruitment by estimating the extent of relatedness between postlarvae settled in the Florida Keys and adult spiny lobsters from geographically remote populations across the Caribbean Sea. Indirect oceanographic modeling methods were used to investigate the transport and retention patterns of spiny lobster larvae in the Caribbean region.

Methods

Results

Conclusion