| genetic and geographic differentiation in the rio negro tuco-tuco (ctenomys rionegrensis): inferring the roles of migration and drift from multiple genetic markers. | among tuco-tucos, ctenomys rionegrensis is especially amenable to the study of the forces driving population differentiation because of the restricted geographic range it occupies in uruguay. within this limited area, the rio negro tuco-tuco is limited to sandy soils. it nonetheless exhibits remarkable variation in pelage color, including melanic, agouti, and dark-backed individuals. two hypotheses have been put forth to explain this pattern: (1) local differentiation and fixation of alternative ... | 2003 | 12778560 |