FROM POPULATION TO GENOME - ECOGENETICS OF LEISHMANIA (VIANNIA) BRAZILIENSIS AND L (V) PERUVIANA

The size polymorphism of nine chromosomes, recognized by specific prob es, was analysed in populations of Leishmania (Viannia) braziliensis a nd L. (V.) peruviana from various Peruvian biogeographical units. Inte rpretation of the polymorphism, by statistical and phenetic methods, l ed to the identification of five consensus (alpha- and beta-tubulin) a nd four variable chromosomes. The dynamics of the variable chromosomes were studied. The promoter role of the environment on their polymorph ism was indicated by: (1) the discrimination of L. braziliensis (fores t) and L, peruviana (Andes) by the size of the chromosome containing t he gp63 genes; and (2) the fact that, within L. peruviana, the polymor phism of the variable chromosomes revealed a strong eco-geographical s tructuring of parasite populations, accompanied by increasing chromoso mal dissimilarity along a dine from north to south. The adaptative sig nificance of the polymorphism of the variable chromosomes was suggeste d by: (1) a correlation between chromosomal polymorphism and phenotype variability (lesion type in patients and virulence in vitro); and (2) the association between the decrease in size of the gp63-containing c hromosome from L. braziliensis to L. peruviana, and a rearrangement of the gp63 genes, probably accompanied by a decrease in their copy numb er. As chromosomal variation was shown to be more dependant on eco-geo graphical differences than isoenzymatic variation, chromosome variatio n and enzyme variation probably differ in adaptative significance.