Genetic variability in the western lowland gorilla (Gorilla gorilla gorilla): Implications for captive management

An assessment of genetic variability within a population can be made by identifying and quantifying genetic polymorphisms. Electrophoretic analysis of red blood cell enzymes and plasma proteins was performed on a study group of 75 gorillas. Chromosomal analysis using G-band and C-band staining techniques were performed on a group of 33 gorillas. Within each study group gorillas were separated into two categories: wild-born and captive-born individuals. Genetic heterozygosity was assessed using electrophoretic polymorphisms identified at four of twenty loci studied. Genetic variability was also measured through analysis of C-band polymorphisms which were identified on all gorilla chromosomes. Frequencies for all identified polymorphisms were calculated. Electrophoretic data showed that total average heterozygosity (H) for the wild-born group equalled 0.042 and within the captive-born H equalled 0.031. These average heterozygosity values were not significantly different though the frequency of heterozygotes at the PGM-1 locus was significantly decreased in the captive-born group as compared to the wild-born group. Chromosomal data showed that total average heterozygosity values for wild-born gorillas and captive-born gorillas was virtually the same, 0.28 and 0.29 respectively. Seventeen low frequency polymorphisms ($\leq$0.13) identified within the wild-born group were not demonstrated in the captive-born group. Neither structural nor numerical abnormalities were observed for any of the individuals studied. C-band polymorphisms were shown to be useful in delineating familial relationships and may prove a suitable tool in determining paternity within large gorilla breeding groups. An overview of gorilla breeding status is presented. Heterozygosity levels are related to founder population size and recommendations are made to maximize the genetic input from the remaining wild-born group, especially those individuals that have not yet produced offspring