Population polymorphism, cladistical congruences and specific recognition of some species of Oryzomys based upon electrophoretic analyses



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Texas Tech University


In an attempt to better understand chromosomal polymorphisms in a population and to evaluate a systematic hypothesis developed from eladistical analyses of G-band chromosomes, an electrophoretic study was conducted on 10 species of the rodent genus Oryzomys along with seven related genera. Electrophoretic data were analyzed by cluster phenograms, Fitch-Margoliash cladograms and a Wagner cladogram. Results indicate that two species existed in a sample from Tafelberg, Suriname, consisting of 10 specimens that previously had been identified as a single species (Koop ejt. aj^., 1983). This conclusion is significant to understanding the nature and origin of chromosomal polymorphism in this sample, because nine different chromosomal polymorphisms present were among these individuals. Dividing this sample into two species partitions all chromosomal polymorphism into one species and separates them from the two individuals that were homoyzgous for all chromosomal rearrangements. Because certain eleetrophoretically identified alleles were not present in the chromosomally polymorphic population and because the other hypothetically required ancestor has not been found, I concluded that the chromosomally polymorphic population is not the result of hybridization between two chromosomally diverse taxa. A Wagner cladogram based on electrophoretic data was compared with a cladogram of relationships developed by Baker e^ al^. (1983) for chromosomal rearrangements and the two were found to be highly concordant. Additionally, to evaluate electrophoretics as a tool in faunal surveys, eight unknown specimens were included for comparison with known taxa. Possible specific designations then were assigned to these specimens on the basis of their similarity to those of certain identification. Also, some specimens from separate geographic localities were noted as potential subjects for additional research because they possibly represent different species. It was concluded that electrophoretic analysis can be a valuable tool in the primary stages of faunal surveys.