Figure 1From: The existence of species rests on a metastable equilibrium between inbreeding and outbreeding. An essay on the close relationship between speciation, inbreeding and recessive mutationsComparing the effects of accumulation of recessive deleterious mutations in populations undergoing various degrees of inbreeding, and with a theoretical completely outbred population. Panel A: Mendelian laws predict that when a crossing occurs between two individuals heterozygous for a recessive deleterious mutation, allelic frequency for that mutation drops from 0.5 in the parents to 0.33 in the offspring. Panel B: Evaluation of the fertility as a function of mutation loads and inbreeding coefficients. The thick red curve corresponds to the fertility predicted in a completely outbred population. It was drawn with the equation F = (1- M2.10-8)10,000 (see text). The thinner curves of different colours correspond to the fertility of crosses with a certain degree of inbreeding, as indicated on the figure. Those were calculated as F = (1- I)M, where F is the predicted fertility, M the average mutation load in the population, and I the inbreeding coefficient. In natural populations, the actual fertility would be a factor of those two theoretical degrees of fertility.Back to article page