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Edge Influence on Reproductive Success of
Symphoricarpos orbiculatus
BreAnne M. Nott1, Elise M. Tulloss2
& Scott J. Meiners1
1 Eastern Illinois University,
Department of Biological Sciences
2 University of California-Davis, Department of Plant Sciences,
Davis, California
Introduction to Edge Effects and S.
orbiculatus
Many have documented the effects of forest edge on
vegetation. At a forested edge there is a greater amount of both biodiversity
and density of vegetative species. There are two mechanisms that can lead to
this distribution of species: dispersal and differential plant performance.
Differences in dispersal is often due to faunal
interactions. Avian species and other herbivorous species are more abundant at
forest edges and can lead to differences in deposition of viable seeds. Abiotic
factors can also contribute to differential spatial patterns of dispersal.
Symphoricarpos orbiculatus, coral berry, is a shrub species that can grow
in both the forest interior and forest edge. S. orbiculatus is found most
predominately at the edge; however, it can also be found in the forest interior.
This species is also very colonial and can asexually reproduce via underground
rhizomes.
This study particularly focused on the differential plant performance of S.
orbiculatus in relation to the edge.
Methods
Measuring Plant Performance
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Twelve 10x4m transects were conducted in Warbler
Woods Nature Reserve, IL
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More than 10 individuals were randomly selected from
each transect at different distances from the forest edge.
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For each individual, the number of branches, number
of stems, number of fruits, and distance from the edge was recorded.
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Fruits from each individual were collected after
ripening and were put through stratification and germination.
Study Questions
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Document spatial patterns of S. orbiculatus in
relation to the edge.
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Assess the vegetative performance of S. orbiculatus
in relation to the population density along the forest edge gradient.
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Evaluate the potential for reproductive variance in S.
orbiculatus in order to generate spatial patterns associate with
edges.
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Figure 1. Symphoricarpos orbiculatus |
Results
Differential Performance of S. orbiculatus.
Population density of declined with distance into the forest, with few
individuals occurring eight meters into the forest. Similarly, total fruit
production by each individual was positively correlated with light
intensity and negatively correlated with distance from the edge. The
quality of offspring produced was unaffected as the weight of individual
seeds and fruits did not change significantly with distance from the edge.
Seeds were ~99% viable for the entire population and did not change in
response to distance along the edge.
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Figure 2. Population density and fruit
production of Symphoricarpos orbicularis across a forest edge
gradient. Data plotted are means ± 1 SE. Line is a best-fit line through
the means at each distance class. Means sharing the same letter are not
statistically different at P<0.05. |
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Figure 3. Response of individual plant
performance to the edge gradient. Best-fit lines are plotted on those
graphs with significant correlations |
Discussion
Plant Performance of S. orbiculatus as a Contributor to Edge
Effects
This study focused on the reproductive performance of S. orbiculatus in
relation to the edge instead of dispersal. The attempt was to determine the
underlying mechanisms behind spatial patterns seen in forest edge systems by
looking at the differential performance of individuals. S. orbiculatus
individuals were shown to have a higher density at the edge and produce more
fruit at forested edges. Plant reproductive performance can thus be a concluded
to be a contributor spatial patterns seen in S. orbiculatus.
Dispersal was disregarded in this study and could influence the density of
vegetation at forest edges.
With increasing amount of forest fragmentation in our environment, forest edges
are increasing and influencing many vegetative species. By using this species as
a model, we will be able to tell the mechanisms behind the spatial patterns seen
in nature and be able to predict the effects of rapidly growing edges on
different species.
Future Research to be conducted on S.
orbiculatus
This study focused on edge effects produced by plant performance. Future studies
need to be conducted to determine the edge effects that dispersal creates on
S. orbiculatus and to conclude if plant performance or dispersal play a
greater role in the distribution of species at forest edges.
Acknowledgements
The Garden Club of America
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