Polymerase-Chain-Reaction (PCR) Analysis of Microsatellites: A New Approach to Studies of Genetic Relationships in Birds

Genomic DNA libraries of the Barn Swallow (Hirundo rustica) and the Pied Flycatcher (Ficedula hypoleuca) were screened for the presence of dinucleotide microsatellite repeats. Two thymine-guanine repeats, “(TG)n,” and two thymine-cytosine repeats, “(TC)n,” were isolated and sequenced from the two species, respectively. Polymerase-chain-reaction (PCR) analysis of 25 unrelated Barn Swallows and 10 unrelated Pied Flycatchers revealed 3 to 15 alleles per locus and heterozygosities in the range of 0.46 to 0.89. Mendelian inheritance was confirmed for all four loci in 10 Pied Flycatcher and 2 Barn Swallow families comprising a total of 240 meioses. The occurrence of nonparental alleles in offspring from two Barn Swallow families was consistent with extrapair fertilization as revealed by a parallel DNA­ fingerprinting analysis. A DNA amount approximately corresponding to 0.01 μl blood was used for PCR analysis. DNA was also prepared from feathers and approximately 1% of a preparation from a single remex or rectrix was sufficient for PCR amplification. One of the primer pairs from the Barn Swallow also amplified a polymorphic locus in the House Martin (Delichon urbica) and in the Bank Swallow (R. riparia).