An evolutionary platform for alternate bearing in fruit trees

Abstract

Alternate bearing has been and still is a major problem in fruit trees. From the point of view of a horticulturist it is a tree productivity syndrome which must be addressed by agro-technical means in order to eliminate or, at least, mitigate the alternation cycle. ‘Masting’ is a widespread forest tree irregular sexual reproduction pattern that has attracted ecologists who wonder about the survival-advantage of this behavior. From an evolutionary perspective alternate bearing and masting seem to be related and may share a common bio-evolutionary mechanism, responsible for ‘yield alternation’. A recently developed resource budget model, based on nonlinear chaos dynamics, seems to account for a broad spectrum of yield alternation patterns. From an evolutionary standpoint, one may envision a domestication-evolutionary continuum from extreme masting, through intermediate alternate bearing, down to regular yield of fully-managed fruit trees. Domestication records of pecan (Carya illinoiensis) support this hypothesis. The alternate bearing of fruit trees appears to be mediated by a ‘fruit overload’ signal but resource depletion still plays a critical role in the alternate bearing of numerous tree crops.