Botryllus schlossen, a compound ascidian is found worldwide in temperate and subtropical shallow waters. This species, which originated in the Mediterranean Sea, has become cosmopolitan via the transportation of colonies attached to ship hulls. Two types of genetic markers (allorecognition alleles on the tunicate fusibility-histocompatibility locus and molecular markers, microsatellites) have been used here to characterize native populations of B. schlossen in the Istra Peninsula, Croatia (the Northern Adriatic Sea). In this area, ship transportation is locally restricted, reducing the possibility of gene flow from remote populations. Allorecognition assays revealed that fusion and rejection responses are similar to those recorded previously from other populations. Pairwise allorecognition assays performed on all combinations (n=120) from 16 colonies resulted in 14.9% rejections, due to the appearance of 10–19 calculated fusibility alleles, not equally frequent. Genetic diversity of two populations was tested by four polymorphic microsatellite loci (4–11 alleles). Hardy-Weinberg exact test for loci revealed a significant heterozygote deficiency, suggesting partial inbreeding. Comparisons with other populations worldwide further indicate the high polymorphism characteristic to this species.
|Title of host publication||The Biology of Ascidians|
|Editors||Hitoshi Sawada, Hideyoshi Yokosawa, Charles C. Lambert|
|Place of Publication||Tokyo|
|Number of pages||10|
|State||Published - 2001|