Introduction - Genetic Diversity in Establishing Plant Populations: Founder Number and Geometry - page 4

spreading the risk of localized demise of entire subpopulations (e.g., due to
local fi re or pathogen attack). Local populations could be intermixed later
when each develops to suffi cient numbers.
In addition to establishing the number of founders to be used, is
it important to consider the geometry of introduction at one location?
Consider the different patterns of introduction depicted in Fig. 1.1. Suppose
a restoration project manager has painstakingly acquired 30 propagules
of an endangered species. It is obvious that planting these 30 founders at
approximately the same point (Fig. 1.1A) would induce severe intraspecifi c
competition with a probably negative effect on population establishment.
At the other extreme, introducing individuals at densities so low that
individuals fail to engage in needed interactions, such as pollination or seed
vector mutual facilitation, would have a negative impact on population
establishment (Allee effects; Fig. 1.1B).
Fig. 1.1 Different patterns of introduction of 30 individuals into a defi ned preserve or natural
habitat. A. Placement of all 30 individuals at approximately the same point creates intense
competition. B. Individuals are randomly, but distantly, spread such that needed interactions
among individuals cannot occur effectively (Allee effects). C. Founders are placed in a central
square at approximate average density for the species. D. Founders are subdivided into
four groups at corners. E. Founders are placed in three rows at one corner. F. Founders are
placed at moderate spacing in the center. In anthropogenic establishment projects, options
E, and perhaps D, would likely be the most economical in terms of ease of introduction and
maintenance, especially if the preserve is large.