Analysis of failure time in clonally propagated plant populations

A problem originating in forest tree breeding concerns the number of clones needed in clonally propagated plantings to manage risk of failure due to an unforeseen catastrophic event. In this paper, we present a model for and analysis of time to failure for clonally propagated populations, assuming that in each year there is a chance for attack by an insect or pathogen. We develop the probability distribution of the number of years until population failure, T. A surprising finding is that in some circumstances increasing the number of clones can increase, rather than decrease, the chance of population failure. This suggests that laws, such as those current in the European Community, mandating minimum numbers of clones to be used in reforestation, may not achieve their intended effects, and that further investigation is needed to clarify the situation.