Oceanography and life history predict contrasting genetic population structure in two Antarctic fish species.

Emma F Young,Gavin J Horsburgh,Jennifer Rock,Lorenz Hauser,Eugene J Murphy,Sonia Pascoal,Mark Belchier,Niklas Tysklind,Gary R Carvalho,Michael P Meredith

doi:10.1111/eva.12259

Abstract

Understanding the key drivers of population connectivity in the marine environment is essential for the effective management of natural resources. Although several different approaches to evaluating connectivity have been used, they are rarely integrated quantitatively. Here, we use a ‘seascape genetics’ approach, by combining oceanographic modelling and microsatellite analyses, to understand the dominant influences on the population genetic structure of two Antarctic fishes with contrasting life histories, Champsocephalus gunnari and Notothenia rossii. The close accord between the model projections and empirical genetic structure demonstrated that passive dispersal during the planktonic early life stages is the dominant influence on patterns and extent of genetic structuring in both species. The shorter planktonic phase of C. gunnari restricts direct transport of larvae between distant populations, leading to stronger regional differentiation. By contrast, geographic distance did not affect differentiation in N. rossii, whose longer larval period promotes long-distance dispersal. Interannual variability in oceanographic flows strongly influenced the projected genetic structure, suggesting that shifts in circulation patterns due to climate change are likely to impact future genetic connectivity and opportunities for local adaptation, resilience and recovery from perturbations. Further development of realistic climate models is required to fully assess such potential impacts.

Highlights

Marine organisms with planktonic early life stages have traditionally been assumed to have high dispersal and weak population genetic structure
Dispersal was highly asymmetric for both C. gunnari and N. rossii for the five study years, with higher values below the diagonal of the connectivity matrix (Fig. 2), indicating unidirectional transport to the north-east across the Scotia Sea in accordance with the dominant north-eastward flows of the ACC
Transport was only bidirectional in the Antarctic Peninsula region, still generally stronger in the north-eastward direction for both species, and for C. gunnari larvae at South Georgia and Shag Rocks

Summary

Introduction

Marine organisms with planktonic early life stages have traditionally been assumed to have high dispersal and weak population genetic structure. Developing an understanding of the key environmental factors and lifehistory stages influencing population genetic structure and connectivity are vital for effective conservation management, and for predicting the potential impacts of future climate change. Such information is especially pertinent in Antarctic waters that are experiencing unprecedented rates of oceanic warming (Meredith and King 2005; Whitehouse et al 2008) and where localized collapses of exploited commercial fishes indicate high vulnerability to marked shifts in trophic relations (Kock 1992)

Methods

Results

Discussion

Conclusion