Mating systems.

Abstract

Patterns of mating vary with the reproductive biology and spatial structure of a species, and combine to influence levels and dynamics of genetic diversity. Knowledge of all aspects of a species' mating system is necessary to understand the distribution of genetic variation between individuals, gene flow within and between populations, what effect human influence may have on these and, therefore, how to best conserve and utilize this variation. This chapter covers the basic processes of tree reproductive biology (sexual systems, incompatibility mechanisms, flowering patterns, pollination processes), their integration to produce observed mating patterns in both temperate and tropical species and some of the methods of quantifying mating systems. Trees are shown to be predominantly outcrossed, but in some species a variety of conditions may lead to a degree of selfing or inbreeding owing to related matings. Abnormal levels of inbreeding may have immediate implications for seed collection, and ex situ conservation strategies, while their long term maintenance may lead to losses of diversity with longer term adaptive consequences.