Variance Effective Population Size for Dioecious Species

The concept of effective population size ( N e ) is an important measure of representativeness in many areas. In this research, we consider the statistical properties of the number of contributed gametes under practical situations by adapting Crow and Denninston's (1988) N e formulas for dioecious species. Three sampling procedures were considered. In all circumstances, results show that as the offspring sex ratio ( r ) deviates from 0.5, N e values become smaller, and the efficiency of gametic control for increasing N e is reduced. For finite populations, where all individuals are potentially functional parents, the reduction in N e due to an unequal sex ratio can be compensated for through female gametic control when 0.28 ≤ r ≤ 0.72. This outcome is important when r is unknown. When only a fraction of the individuals in a population is taken for reproduction, N e is meaningful only if the size of the reference population is clearly defined. Gametic control is a compensating factor in accession regeneration when the viability of the accession is around 70 or 75%. For germplasm collection, when parents are a very small fraction of the population, maximum N e will be approximately 47 and 57% of the total number of offspring sampled, with female gametic control, r varying between 0.3 and 0.5, and being constant over generations.