ABSTRACT

While migration of individuals has been shown to increase the persistence of small isolated populations, the role that pollen-mediated gene flow may have on population viability is not known empirically. In this study, I investigate the consequences of limited gene flow in newly established colonies within a regional metapopulation of Silene alba (Caryophyllaceae) (Anto-novics et al., 1994). Given that colonisation events are frequent, but that they often fail, I focused on factors that influence colonisation success. In particular, I examined the extent of inbreeding and gene flow in isolated colonies. In addition to these empirical approaches, a simulation model was used to examine the interaction of inbreeding and demographic stochasticity on population persistence and metapopulation spatial structure. The chapter reviews theoretical and empirical studies pertinent to the viability of new established colonies and uses work related to the S. alba system as a case study.

OVERVIEW: SPATIAL STRUCTURE, GENETICS DEMOGRAPHY AND POPULATION ESTABLISHMENT

It is generally accepted that most plant species are not uniformly distributed over space, but are often divided into subpopulations that are interconnected to varying degrees through dispersal of pollen and seeds. Spatial subdivision, local extinction and colonisation have long been recognised as important features of natural populations by both ecologists addressing the broad issues of distribution, abundance and community structure of species and geneticists interested in localised adaptation and evolution. These two distinct approaches to a common population structure are in part a legacy of biogeographic theory advanced by MacArthur & Wilson (1967) and early work of Wright on genetic structure and adaptation (1931).