Biochemical Genetics, Vol. 43, Nos. 5/6, June 2005 ( C  2005) DOI: 10.1007/s10528-005-5212-9 Genetic Structure of Blastocerus dichotomus Populations in the Paran´ a River Basin (Brazil) Based on Protein Variability E. J. F. de Oliveira, 1,3 J. E. Garcia, 1,2,3 E. P. B. Contel, 1,3,4 and J. M. B. Duarte 2,3 Received 12 December 2003—Final 13 May 2004 The population structure of 147 marsh deer (Blastocerus dichotomus) from three areas in the Paran´ a River basin, Brazil, was studied by observing protein polymor- phism at 17 loci. Six loci were polymorphic and 11 monomorphic. The proportion of polymorphic loci (P) was 35.29% and the average heterozygosity (H) was 6.31%. Wright’s F ST indicated that only 4.9% of the total variation in allelic fre- quencies was due to genetic differences between the three groups. The high value of F IS (0.246) indicated inbreeding in the marsh deer. Genetic distance values (D = 0.014–0.051) showed little divergence between the three areas. We suggest that probable mechanisms accounting for the genetic structure are female phy- lopatry and polygyny and also that inbreeding has resulted from decreasing areas of wetland leading to isolation, overhunting, and diseases transmitted by cattle. KEY WORDS: Blastocerus dichotomus; marsh deer; genetic variability; population genetics. INTRODUCTION One of the gravest problems facing wild animal conservation work is the breakup and separation of the habitats of populations of given species. Habitat elimination can affect a species in various ways, and if its rate of dispersal is insufficient, the 1 Department of Genetics, School of Medicine, University of S˜ ao Paulo, 14049-900 Riber˜ ao Preto, SP, Brazil. 2 Department of Zootechny, School of Agrarian and Veterinary Science, State University of S˜ ao Paulo (UNESP), 14870-000 Jaboticabal, SP, Brazil. 3 Brazilian Deer Conservation Project. 4 To whom correspondence should be addressed; e-mail: epbconte@rge.fmrp.usp.br. 211 0006-2928/05/0600-0211/0 C  2005 Springer Science+Business Media, Inc.