MEPS 486:121-132 (2013)  -  DOI: https://doi.org/10.3354/meps10373

Eelgrass Zostera marina populations in northern Norwegian fjords are genetically isolated and diverse

Jeanine L. Olsen1,*, James A. Coyer2, Wytze T. Stam1, Frithjof E. Moy3, Hartvig Christie4, Nina Mari Jørgensen5

1Marine Benthic Ecology & Evolution Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Nijenborg 7, 9747 AG Groningen, The Netherlands
2Shoals Marine Laboratory, Cornell University, 400 Little Harbor Rd., Portsmouth, New Hampshire 03801, USA
3Institute of Marine Research, Research Station Flødevigen, 4817 His, Norway
4Norwegian Institute for Water Research, NIVA, Gaustadallen 21, 0349 Oslo, Norway
5Akvaplan-NIVA, Fram Centre, 9296 Tromsø, Norway

ABSTRACT: Populations along the northern boundary of a marine species’ distributional range in the NE Atlantic are expected to harbor lower standing genetic variation as a consequence of post-glacial expansion following the last glacial maximum. Founder events and marginal habitat availability may render the edge populations more vulnerable to anthropogenic stress and less capable of rapid adaptation to global climate change, a concern for conservation and management. We analyzed meadow architecture, persistence and connectivity within and among 15 locations (600 samples genotyped with 8 microsatellite loci) in 3 fjords in Troms County, Norway (69°N). Whereas global mean allelic diversity (standardized for sample size) was in accordance with previous studies using the same markers, more extensive sampling revealed a broader range of allelic richness (mean = 2.85; range = 1.84 to 4.21) in the regional pool. Genotypic diversity was typically high, whereas large genets were rare (2 out of 15 locations). Population differentiation (FST) was 2 to 6 times higher between fjords than within fjords. A Bayesian (STRUCTURE) analysis also strongly supported the genetic distinctness of each fjord. Although 9 locations within the 60 km long Balsfjord were connected by gene flow, demographic connectivity may actually be low, as fixed differences were observed at 6 of the 9 locations, along with significantly positive inbreeding coefficients and strong substructure. Overall, our results suggest that these northern, leading-edge meadows are healthy, but vigilance is required to avoid further losses. Fjord-level management, especially of the larger fjords, will be sufficient to capture the range of variation.


KEY WORDS: Seagrass · Zostera marina · Populations · Genetic diversity · Management · Leading-edge


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Cite this article as: Olsen JL, Coyer JA, Stam WT, Moy FE, Christie H, Jørgensen NM (2013) Eelgrass Zostera marina populations in northern Norwegian fjords are genetically isolated and diverse. Mar Ecol Prog Ser 486:121-132. https://doi.org/10.3354/meps10373

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