Perennials - Genetic Diversity in Establishing Plant Populations: Founder Number and Geometry - page 219

the introduction of a shrub that can be considered a mid-successional species
of mesic environments that eventually becomes overtopped as forests reach
climax. In the trials examined below, we arbitrarily designate the maximum
lifespan of this shrub to be 60 years (the maximum can be specifi ed by the
user). Thus, these trials are meant to explore some of the circumstances that
might surround attempts to reintroduce a rare or endangered dioecious
shrub such as Allocasuarina portuensis (Casuarinaceae) of Australia or Corema
conradii (Empetraceae; endangered in parts of northeastern North America),
or even restoration or introduction of populations of non-endangered
species such as Lindera benzoin (spicebush; Lauraceae) to new or formerly
occupied habitats.
The modeling below is intended to explore the consequences of
variation in several initial conditions for establishing spicebush populations.
This species is a short shrub-bush-treelet (often with multiple grouped
stems) growing to 4 m or so at good sites. Spicebush prefers richer moist
(not constantly wet) soils, and so is often found in fl ats and valleys, with
presence diminishing or failing altogether upslope. Populations can thus
have a linear aspect along streams or in areas with defi ned relief (which
could also be modeled with NEWGARDEN). Birds appear to be the main
dispersal vector of fruit (single seeded), the list including American Robin,
Northern Bobwhite, Gray Catbird, Eastern Kingbird, and Great Crested
Flycatcher. Records indicate that raccoons and Virginia opossums consume
the fruit as well.
We begin by describing the trial that forms the basis for the next series
of trial comparisons for a perennial dioecious shrub, trial M. A fi rst set of
trials will be compared to trial M to examine the effects of spatial placement
of founders, as well as alterations in offspring or pollen dispersal distances
on population growth and subsequent genetic diversity.
Basic trial M input follows (note: basic trial m is exactly the same except
that the 172 founders are not placed in a central square, but are divided
into four groups of 43 founders each, one group at each corner, as will be
explained later). Some aspects of the basic trial M input will be explained
in increased detail since this is the fi rst perennial to be analyzed:
30 loci, each with 100 different alleles of equal frequency = 0.01, are
analyzed.
<Dioecious value=“true”/>
Offspring are not produced until age x=8, and then offspring production
ramps up to a maximum of 1.3 from age 13 through 45. Offspring production
then declines until age 55 (100% mortality occurs at age 60; see below).
<Reproduction_Rate>
<functionpoint x=“0” y=“0”/>