Biology Reference
In-Depth Information
2
CHAPTER
What NEWGARDEN Does
The computer program NEWGARDEN is designed to help conservation
or evolutionary biologists, as well as students, explore how the number of
founders, the geometry of the initial spatial positioning of the founders, and
life history characteristics of a given species interact to infl uence the growth
rates of colonizing plant populations and their retention of genetic diversity.
In a given NEWGARDEN analysis trial, the user specifi es the initial
conditions for population establishment and continuing development, and
by changing these specifi cations in alternate comparative trials, the user
can explore the effects of varying one or a few conditions or factors in
combination on population growth and genetic diversity over generations.
The NEWGARDEN populations that develop according to the specifi ed
input conditions are simulated populations for which each new generation is
created as a result of virtual matings between individuals as brought about
by those user-defi ned input specifi cations. In other words, the generations
develop not on the basis of general theoretical modeling formulas, but rather
via virtual matings and offspring production controlled by user-defi ned
parameters and resulting population growth phenomena described below.
The program is designed to be easy to use so that it can be employed, with
a little practice, by a wide range of practitioners, including students. To
make the principles involved more accessible to a wide audience, below
we review relevant basic concepts that practicing biologists steeped in
population genetics can skip over. Students new to these concepts would
benefi t from consulting texts offering more extensive treatments (e.g., Hartl
and Clark 2007; Hedrick 2010).
In using NEWGARDEN, many outcome patterns will be obvious, at
least to the experienced population geneticist. However, we hope that all
users will fi nd at least some patterns that are newly instructive, and we
have noted that several interesting and important features of establishment
of small populations that emerge from the trials described below are not
widely discussed in basic conservation and population genetics texts. In
fact, some of the results suggest a neglected area of restoration theory and
research: spatially induced effects on genetic diversity retention, random
drift, and population establishment. When outlining our conclusions in this
regard, we argue that spatial effects will sometimes drive non-Darwinian
evolutionary processes.
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