Highly polymorphic microsatellite loci in the colonial ascidian Botryllus schlosseri.

Five mircosatellite loci are characterized for the colonial ascidian Botryllus schlosseri. Within one population from Monterey, California, these loci have 3 to 17 alleles, observed heterozygosities from 0.40 to 0.63, expected heterozygosities from 0.52 to 0.84, and an overall paternity exclusion rate (QT) of 0.78. Three of the five loci demonstrated Mendelian patterns of inheritance in laboratory crosses. The size distribution of alleles suggests that most allelic diversity within these loci is generated by single-step and less frequently multistep mutations. However, several alleles may also have been generated by single based insertions or deletions. Mutation rates for the five microsatellite loci are less than 1 x 10(-2) per generation. Because or their highly polymorphic nature, these loci should prove useful for exploring issues of identity, kinship, population structure, and phylogenetics.