Genetic flexibility: A model for determining the range of suitable environments for a seed source

A mathematical model describing the relative performance of different seed sources over a range of environments has been developed and tested using data from Scots pine in Sweden and white ash in USA. The components of the model have a direct biological interpretation in terms of the fundamental nature of the problem: i.e. the maximal performance of a seed source, where this maximum will occur and the range of suitable sites for such a seed source. Comparisons can thus be made between seed sources as to their site perferences and the relative flexibility of each seed source calculated. Decisions regarding the optimal deployment of seed may thus be simplified and such information used to refine the allocation of breeding zones. The model requires that a one-dimensional environmental gradient be defined. Such gradients may relate to a single overriding environmental factor (e.g. winter cold) which can be described by geographical information such as latitude, altitude and distance from the sea. Definition of this gradient is a necessary prerequisite to application of this model. Methods for establishing such gradients are discussed.