The influence of seed dispersal mechanisms on the genetic structure of plant populations

Abstract

The plant electrophoretic literature was reviewed to determine whether seed dispersal mechanisms effectively predict the distribution of genetic variation within and among plant populations. To consider the relationship between seed dispersal and genetic differentiation on a local scale, nine species of tropical trees from the same lowland forest community in Panama were examined electrophoretically. In both cases, the association between seed dispersal and the distribution of genetic variation was not as significant as expected. To better understand the processes underlying the development of genetic structure within plant populations, the genetic consequences of two generalized patterns of seed dispersal were explored. In the Platypodium model, seeds were wind disseminated and leptokurtically distributed, while the Piper model had the highly clumped dispersal pattern characteristic of many species with animalingested seeds. Variable breeding structures and the selective mortality of seeds and seedlings were also incorporated, since these factors can have important effects on population structure. The problem of obtaining quantitative estimates of these evolutionary parameters from natural populations is discussed. An analytical procedure (paternity exclusion analysis) is suggested which could be instrumental in elucidating those mechanisms which interact to produce genetic structure in natural plant populations.