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Title: Genetic variability and level of differentiation in North Sea and Baltic Sea populations of the green alga Cladophora rupestris
Authors: Johansson, G.
Sosa, P. A. 
Snoeijs, P.
UNESCO Clasification: 240903 Genética de poblaciones
241714 Genética vegetal
Keywords: Genetic Differentiation
Marine Alga
Salinity Gradient
Average Gene Diversity
Issue Date: 2003
Publisher: 0025-3162
Journal: Marine Biology 
Abstract: Cladophora rupestris is a perennial filamentous macroalga belonging to the Chlorophyta. It is widely distributed on both sides of the northern Atlantic Ocean and penetrates into the brackish Baltic Sea down to ca. 4 psu salinity. In this paper we present evidence for genetic differentiation of a Baltic form of this marine alga. We assessed genetic structure within and among 11 populations ranging along a salinity gradient from the Norwegian coast to the northern Baltic Sea proper. Samples of 328 individuals were studied using starch-gel protein electrophoresis to evaluate genetic variability and interpopulation differentiation based on allozymes. Of 11 loci examined, only one was polymorphic. For this locus, encoding superoxide dismutase (SOD-3), a total of seven alleles were distinguished. We found two genetically differentiated groups of populations of C. rupestris, one Baltic Sea group and one North Sea group, with a distinct border in the southern Kattegat near the entrance to the Baltic Sea. The genetic differentiation for SOD-3, expressed as pairwise F ST values between the populations, was generally higher within the Baltic Sea group (0.10–0.43) than within the North Sea group (0.05–0.10); in the latter group also fewer pairs of populations differed significantly. Pairs of populations from different groups had the highest F ST values (0.20–0.60). Hierarchical analysis of variance showed that 29.6% of the total variation in the SOD-3 locus was explained by variation between the two groups, while only 4.2% was explained by variation among the populations within the groups. The remaining variation (66.2%) was found within the populations.
ISSN: 0025-3162
DOI: 10.1007/s00227-003-1023-x
Source: Marine Biology [ISSN 0025-3162], v. 142, p. 1019-1027
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