Lineage loss in Serengeti cheetahs: Consequences of high reproductive variance and heritability of fitness on effective population size

In natural populations, many breeders do not leave surviving offspring, and as a result many potential genetic lineages are lost. I examined lineage extinction in Serengeti cheetahs (Acinonyx jubatus) and found that 76% of matrilines were lost over a 25-year period. Production of future breeders was nonrandom and generally confined to a few families. Five out of 63 matrilines accounted for 45% of the total cheetah population over the course of the study. Lineage persistence is perhaps best illustrated by the variance in lifetime reproductive success (LRS) and heritability in this parameter. In female cheetahs, variance in LRS wa high, and new data show that this LRS was heritable. Variance in LRS and heritability in LRS have dramatic consequences for effective population size, N-e. I calculated N-e for cheetahs, taking into account fluctuating population size, unequal sex ratio, non-Poisson distribution of reproductive success, and heritability of fitness. The N-e was most strongly affected by variance in reproductive success and especially heritability in reproductive success. The variance N-e was 44% of the actual population size, and the inclusion of heritability further reproduced N-e to only 15% of the actual population, a ratio similar to that of a social carnivore with reproductive suppression. The current cheetah population in the Serengeti is below numbers suggested by N-e estimates as sufficient to maintain sufficient genetic diversity.