Evolutionary trends in mammalian trypanosomes.
Publisher Summary This chapter discusses the multiformity of variation and the heterogeneity among mammalian trypanosomes, which have furnished abundant material for deductions regarding the evolution of these haemo-flagellates. Evidence of some of the phases of the evolutionary process is provided by certain “relict” species, while indications of incipient speciation are found among infrasubspecific strains or demes exhibiting minor biological divergence. The gradual transition from one morphological and biological type of trypanosomes to another, as well as the progressive complication of the life cycles and mode of transmission of these parasites, supply clues to their phylogenetic relations. These, in their turn, serve as a basis for the natural classification of the mammalian trypanosomes.