Biology Reference
In-Depth Information
exist in following successive generations will occupy an assigned (x,y) grid
point and prevent other individuals from occupying that grid point, until
it dies. While for the founders exact grid placement is user-specifi ed, for
subsequent NEWGARDEN-produced individuals, NEWGARDEN grid
location assignments are random, conditioned by other input specifi cations
(e.g., dispersal distance probabilities). As NEWGARDEN generates the
next cohort, two or more offspring may be dispersed to the same grid
point. After NEWGARDEN has generated all potential offspring for a new
cohort, if multiple offspring have been assigned to the same grid point,
NEWGARDEN randomly selects one of these to occupy that point in the
realized cohort, and the other co-occupiers are removed immediately (die)
and do not participate in any further program analyses.
Distance is defi ned in grid points. So, two individuals may have
three grid points between them, or microgametes or an offspring may be
dispersed to a grid point 12 grid units from a parent. It is possible for an
individual to be dispersed to a point off the grid. For example, consider
an individual 3 grid units from the border. If offspring dispersal distance
has been set to a maximum of 7 grid units, then when NEWGARDEN
randomly selects a point for offspring establishment, it is possible that a
point beyond the border will be selected. Individuals dispersed to points
off the grid die immediately (are removed from the population data set)
and cannot contribute microgametes or offspring to future generations, nor
play any role in future analyses.
A quadrangular system of grid points, the preserve, at which
individuals can establish can be created by the user with statements similar
to the following:
<Region XL=“-4960” XH=“6303” YH=“2559” YL=“-2560”>
<Rectangle XL=“-4960” YL=“-2560” XH=“159” YH=“2559”/>
</Region>
The Region statement defi nes the entire grid system that NEWGARDEN
establishes. It
does not
defi ne the preserve. It merely establishes the region
in which the preserve will exist. The actual preserve, which includes all
and only the points where individuals can establish, is defi ned by the
Rectangle statement. In the example above, both the Region and the
Rectangle statements defi ne the grid system and preserve, respectively,
by specifying the four corners of each: XL = lowest number on the x-axis;
XH = highest number on the x-axis; YL = lowest number on the y-axis; and
YH = the highest number on the y-axis. Thus, the preserve described in the
Rectangle statements above has the following corner points, starting from
the bottom left: (-4960, -2560), (159, -2560), (159, 2559), and (-4960, 2559).
Including the ordinate and abscissa intersection point (at point (0,0)), this
preserve is 5120 average plant density points on a side, giving a maximum
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