Published online by Cambridge University Press: 14 April 2009
In a series of Lacerta vivipara samples from southern France's central mountains, the distribution of genotypes at the mannose phosphate isomerase (MPI) locus has only been accountable as due to sex linkage in female heterogamety, provided the W chromosome carries only one of the two observed alleles in the populations sampled. This is in perfect accordance with cytogenetical data. Reasons are presented that seem to limit acceptable hypotheses for the recent origin of this sex-linked polymorphism to three: a founder effect, a point mutation in Z chromosomes after crossover suppression, or hitch-hiking with the translocation involved.