Optimization theory in plant evolution: An overview of long-term evolutionary prospects in the angiosperms

Abstract

Examination of literature shows that a number of authors regard outbreeding and heterozygosity as the prevalent factors associated with long-term successful evolution in the angiosperms. A number of plant evolutionists, however, have doubted the truth of such an assumption. Everincreasing reports of the existence of arboreal angiospermous apomixis in tropical forests of the Neotropics and the Far East undermined a thinking which, recently, has rested on optimality. Finding apomixis in trees surprised authors, who held biased opinions about the determinism of outbreeding as the major guiding factor in the evolutionary history of the angiosperms. The thinking that apomixis may turn out to be a regular mating system of the flowering plants met with the approval of some authors, who wondered about the true penetration of the phenomenon among the higher plants. The fact that one-third of all known flowering plants are autogamous has cast further doubt on the deterministic infallibility of outbreeding and successful long-term evolution. Despite claims that the breeding system is directly involved with fitness, while determining the course of optimized evolution, there is comparatively little hard evidence to substantiate a hypothesis which, in the last analysis, has rested principally on common sense. Rather, if continuing field research happens to unveil new cases of woody angiospermous apomixis, a prediction is advanced that the next two biomes to show regular incidence of the phenomenon are Africa’s paleotropical savannas and humid forests. If evolution is partly or wholly dependent on the breeding system to proceed, current knowledge supports views that further enhancement of organic diversification vis-à-vis selection and adaptednesss rests on three major tested mating systems: outbreeding, inbreeding and apomixis.