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Marine Ecology Progress Series

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MEPS 290:89-96 (2005)  -  doi:10.3354/meps290089

Population genetics of Zostera noltii along the west Iberian coast: consequences of small population size, habitat discontinuity and near-shore currents

Onno E. Diekmann1, James A. Coyer2, Joao Ferreira1, Jeanine L. Olsen2,Wytze T. Stam2, Gareth A. Pearson1, Ester A. Serrão1,*

1CCMAR – CIMAR Laboratório Associado, Universidade do Algarve, FCMA, Gambelas, 8005-139 Faro, Portugal
2University of Groningen, Biological Center, PO Box 14, 9750 AA Haren, The Netherlands
*Corresponding author. Email:

ABSTRACT: The effects of oceanographic patterns on marine genetic biodiversity along the SW Iberian Peninsula are poorly understood. We addressed the question of whether gene flow in this region depends solely on geographic distance between isolated patches of suitable habitat or if there are superimposed effects correlated with other factors such as current patterns. Zostera noltii, the dwarf eelgrass, is the keystone habitat-structuring seagrass species on intertidal mudflats along the Iberian west coast. We used 9 microsatellite loci to analyze population genetic diversity and differentiation for all existing 8 populations from NW Spain (Ria de Vigo) to SW Spain (Puerto Real, Cadiz). Populations are highly genetically differentiated as shown by high significant FST,Wright’s fixation index, (0.08 to 0.26) values. A neighbor-joining tree based on Reynold’s distances computed from allele frequencies revealed a split between northern and southern populations (bootstrap support of 84%). This pattern of differentiation can be explained by (1) ocean surface current patterns present during Z. noltii’s reproductive season which cause a dispersal barrier between the northern and southern populations of this region, (2) habitat isolation, due to large geographic distances between suitable habitats, preventing frequent gene flow, and (3) small effective population sizes, causing high drift and thus faster differentiation rates.

KEY WORDS: Phylogeography · Dwarf eelgrass · Seagrass conservation · Iberian Peninsula biogeography · Portuguese coast

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