Transcript Wesner - York College of Pennsylvania

Comparing aquatic macroinvertebrates communities between native and invasive plant species in Mill Creek
Shelly Wesner
Department of Biological Sciences, York College of Pennsylvania
1.0
0.5
4g dry= 9.971g wet
•Leaf Packs were assembled into mesh bags with fresh
leaf mass in each bag (amount equivalent to 4g dry
mass).
•The packs were secured into Mill Creek at 15 sites,
each site containing 1 pack of each plant species.
•After 6 weeks leaf packs were retrieved from creek.
• Silky Dogwood (a native) and Tree-ofHeaven (an invasive) had much less
remaining leaf matter compared to BoxElder (a native) and Japanese Knotweed
(an invasive).
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• Japanese Knotweed (an invasive) had the
most remaining leaf matter of the four
plant species.
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4
6
-0.2
Wet Weight (g)
Figure 2. Mean (± 95%CI) taxa richness of aquatic macroinvertebrate
communities did not differ among the 4 species of foliage (P > 0.05, KruskalWallice Test), Japanese Knotweed and Silky Dogwood n = 5, Tree-of-Heaven
and Box-Elder n = 4.
JK
BE
TH
SD
Figure 5. Mean (± 95%CI) dry weight of remaining leaf mass found within leaf
packs differed among the four species of foliage ( P < 0.05, ANOVA). An initial
calculated amount of fresh leaf mass equal to 4 grams of dry leaf mass was in
each pack at the start of the experiment. Japanese Knotweed and Silky
Dogwood n = 15, Tree-of-Heaven and Box-Elder n = 14.
Discussion
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JK
SD
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TH
BE
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• My results are similar to those of Nevin
(2005) and suggests that
macroinvertebrates may not be
negatively impacted by invasive plant
species.
A
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A
B
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• Indeed, there may be positive effects.
B
• Japanese Knotweed (an invasive) does
not degrade as quickly as native species
and therefore may provide a longer
lasting source of food and protection.
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-0.5
TH
SD
JK
BE
Figure 3. Mean (± 95%CI) evenness of aquatic macroinvertebrate communities
did not differ among the 4 species of foliage (P > 0.05, Kruskal- Wallice Test),
Japanese Knotweed and Silky Dogwood n = 5, Tree-of-Heaven and Box-Elder
n = 4.
Evenness
•In October leaves of Japanese Knotweed, Silky
Dogwood, Tree-of-Heaven, and Box-Elder were
collected at Mill Creek.
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Diversity (H )
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Japanese Knotweed
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Horsehair worm
Tree-of-Heaven
Box-Elder
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0.75
1.25
0
0
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Flatheaded mayfly larvae
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Netspinner
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1.75
1.25
Riffle bettle
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0.2
0
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Freeliving caddisfly
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0
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Midge
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4
1
1.75
Shrimp
0
0.2
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0
Riffle bettle larvae
0
0.2
0.25
0
Mayfly
0
0.2
0
0
Water mite I
0
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0.25
Water mite II
0
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0.25
Water mite III
0
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0
0
Water mite IV
0
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0.25
0
JK: Japanese Knotweed
Water mite V
0
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0
Water mite VI
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0.25
SD: Silky Dogwood
Water mite VII
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0
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Muscid
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JK
Silky Dogwood
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• Tree-of-Heaven (an invasive) appears to
be an emphermal resource and therefore
may be of limited value for food and
protection.
Table 1. Mean aquatic macroinvertebrate abundance per leaf pack (Japanese
Knotweed and Silky Dogwood n=5, Tree-of-Heaven and Box-Elder n=4).
2.5
Methods
• There were no significant differences in
taxa richness, evenness, and diversity
between the plant species.
I
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Remaining Dried Leaf Mass (g)
I hypothesize that there will be no
significant difference between the native and
invasive plant species concerning
macroinvertebrate richness, evenness, and
diversity. This hypothesis is based on prior
research by Nevin (2005).
Results
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Taxa Richness
As invasive plant species overtake native species, the
composition of plant communities can change. Researchers
have suggested that the changes in forest composition could
potentially affect a whole ecosystem (Rubbo and Kiesecker
2004). Most research has focused on the effect of the
changing forest composition on forest ecology, but research
on the effects in nearby aquatic environments is lacking with
the exception of Nevin (2005).
Within creeks, aquatic macroinvertebrates form
communities in natural leaf packs. As leaf litter falls into
nearby streams, they are swept by the current and can
accumulate on large rocks and branches forming leaf packs.
These packs become inhabited by a variety of aquatic
macroinvertebrates as a protection from predators and as a
food source (Smith 1986). By breaking down the leaf matter
and exploiting essential nutrients, the macroinvertebrates play
a critical role in the food web. As changes in forest
composition occurs the macroinvertebrate community
composition within leaf packs can be altered.
I conducted a study to determine if invasive plant species
have a negative impact on leaf pack communities in a
Pennsylvania creek by comparing two native plant species,
Box-elder (Acer negundo) and Silky Dogwood (Corunus
amomum), to two invasive plant species, Japanese Knotweed
(Polygonum cuspidatum) and Tree of Heaven (Ailanthus
altissima).
Figure 4. Mean (± 95%CI) diversity of aquatic macroinvertebrate communities
did not differ among the 4 species of foliage (P > 0.05, Kruskal- Wallice Test),
Japanese Knotweed and Silky Dogwood n = 5, Tree-of-Heaven and Box-Elder
n = 4.
Dogwood
Dry Weight (g)
Introduction
Figure 1. Total weight of dogwood wet leaves per pack dependent on 4g of
dry weight. Graphs were made for all four plant species.
SD
TH
X-axis Figure Legend
•Macroinvertebrates were separated from the leaf
material and identified.
TH: Tree-of-Heaven
•Remaining leaf mass was dried and weighed.
BE: Box-elder
BE
• Further studies should consider a greater
sample size.
Works Cited
Nevin, Andrew. 2005. Impact of exotic tree species foliage on aquatic
macroinvertebrate diversity in two Pennsylvania streams. York College Thesis.
Rubbo, Michael J, Kiesecker, Joseph M. 2004. Leaf litter composition and
community structure: translating regional species changes into local dynamics.
Ecology. 85(9):2519-2525.
Smith, David L. 1986. Leaf litter processing and the associated invertebrate fauna in
a tallgrass prairie stream. American Midland Naturalist. 116(1):78-86.
Acknowledgements
I want to thank Dr. Kleiner for his continued support and
advice throughout the project. I would also like to thank the
Biology Department for the opportunity to conduct research.