MEPS 152:131-143 (1997)  -  doi:10.3354/meps152131

Three Australian (Cockburn Sound, Western Australia; Adelaide, South Australia; Port Phillip Bay, Victoria) and four European (Roscoff, Atlantic; Alicante, Carteau, and Marseille, all from the Mediterranean Sea) populations of Sabella spallanzanii were examined for variation at 23 allozyme loci. Levels of genetic variation were high, with average heterozygosities per locus ranging from 0.20 to 0.21 for the Australian collections, and from 0.23 to 0.27 for the European collections. The 3 Australian collections were genetically very closely related to one another, with no statistically significant differences at any of the 15 variable loci. This suggests either an introduction to one port, with a subsequent spread to other areas, or separate introductions with subsequent extensive gene flow. The 4 European collections showed limited, but significant, differentiation among themselves at 10 of 18 variable loci. Much of the heterogeneity reflected differences between the Roscoff (Atlantic) collection and the 3 Mediterranean collections. The Roscoff collection was less variable, in terms of both heterozygosity and mean numbers of alleles, than the Mediterranean collections. The Australian collections were more closely related to the Mediterranean collections (mean Nei distance = 0.040) than to the Roscoff collection (mean Nei distance = 0.084). If a Mediterranean origin is assumed, then the introduction to Australia was accompanied by the loss of about 18% of the original variation. Finally, the high genetic similarity of the Australian to the European collections of S. spallanzanii, and the very clear genetic separation of S. pavonina (mean Nei distance = 0.996), reaffirms that the Australian collections are truly S. spallanzanii and not an undescribed native species.

Sabella · Allozyme · Polymorphism · Genetic differentiation · Founder effect · Introduction