Complex evolution of a salmonid microsatellite locus and its consequences in inferring allelic divergence from size information

Sequence analysis of 78 alleles of a microsatellite locus was resolved atvarious taxonomic levels among salmonid fishes to test for congruencebetween size and sequence information. Allelic variability of this locusinvolved changes in number of dinucleotide repeats as expected formicrosatellite loci. However, additional mutational events involving largeindels and base substitutions also occurred frequently among and withinspecies. These caused the evolution of different imperfect microsatellitevariants, from an ancestral perfect one, which was undetectable fromallelic size information only. Alleles of the same length resulting fromdifferent mutational events were also observed among and within species.Altogether, these results revealed the incongruence between size and numberof mutation events, implying that it may be imprecise to interpretmutational rates and relationships on the basis of size information alonein interspecific comparisons and, to a lesser extent, within species.