Microsatellite Loci and Population Structure in the Platypus.

Abstract

To investigate the genetic relationships within and between platypus populations, molecular genetic methods employing DNA analysis are very effective, and microsatellite variation has been shown to be the most effective for population studies. Microsatellites are segments of DNA with tandem repeats of short sequence motifs, usually 1-6 base pairs of nucleotides, and they are highly variable and easy to score. Several microsatellite loci have been detected and sequenced, and PCR primers have been constructed and used to identify several polymorphic microsatellite variants. In the main breeding population, from which we have a collection of over 80 animals, two alleles not found among resident or other captured males were detected amongst juveniles. From our combination of microsatellite and mtDNA analysis, these alleles are likely to be derived from uncaptured transient males which participated in breeding. We therefore suggest that the mating system in this population of platypus involves polygyny and sneaking. Allele frequency differences have been detected between sub-populations within the same stream, consistent with observations on mtDNA genotypes. As well, there are allele frequency differences between populations from different streams and these show continuous geographical gradation, consistent with an isolation-by-distance geographical structure.