[i] MIT primers were obtained from Research Genetics, nucleotide sequences are given as 5′ to 3′ directions.

[ii] Type of polymorphism detected in the relative PCR fragment, including nucleotide variations for single nucleotide polymorphisms.

[iii] Minus logarithms of P values obtained by Fisher’s exact test (see Methods for further details).

[iv] Direct oligonucleotide sequence of the NGP/N, STS/A, andM. spretus alleles (data from Chen et al. 1994 for the other alleles).

[v] Polymorphism described in Matzinger et al. (1997).

[vi] (NI) Not informative; polymorphisms among strains not detected.