PATTERNS OF EVOLUTION IN GRAOMYS GRISEOFLAVUS (RODENTIA, CRICETIDAE) .1. PROTEIN POLYMORPHISM IN POPULATIONS WITH DIFFERENT CHROMOSOME-NUMBERS

Protein polymorphism has been studied by means of starch gel electroph oresis of tissue extracts in three population samples of Graomys grise oflavus collected at different sites in central-west Argentina. Indivi duals from two of the samples had chromosomal number 2n = 42 and those from the other sample, 2n = 38, 37 or 36. A total of 28 loci were ana lyzed. High levels of variability were observed in three samples (P ra nging between 0.46 and 0.66; H-c from 0.160 to 0.188). Genetic distanc e values between populations with different chromosome numbers were 0. 088 and 0.093. Tests in the laboratory showed the existence of post-zy gotic reproductive isolation between animals with 2n = 42 and those wi th 2n = 38, 37 or 36.