Odum Conference Poster Abstracts
Theme A
Theme B
Theme C
Theme D
Poster Home
Printer-friendly
Abstracts
Theme B: Basic research on dynamic aspects of invasions
* indicates presenting author.
Adams, David*; Roblee, Kenneth; Stone, Ward – NYS DEC Office of Invasive Species Coordination
NYS waterbird mortality as a result of Type E botulism and nonnative invasive species
Periodic waterbird mortality, due to type E botulism (Clostridium botulinum)
intoxication, has been documented on the Great Lakes since the 1960s. The most recent
series of events are unique in that they appear to be linked to population increases
of two nonnative invasive species, the quagga mussel (Dreissena bugensis) and the
round goby (Neogobius melanostomus).
The first documented mortality in New York State occurred in the eastern basin of
Lake Erie November 2000. To monitor impacts on waterbirds, thirteen 500-meter
shoreline transects were established and monitored weekly. Surveys were repeated
during fall 2001 through 2008. By extrapolation we estimate that up to 5415, 2862,
17301, 3008, 5943, 2297, 4375, 8915 and 2005 waterbirds may have died.
In an effort to detect increases in the geographic extent of these annual mortality
events, forty-seven 500-meter transects were placed at five mile intervals along the
Lake Ontario shoreline during 2002. These transects were monitored weekly during the
peak of Common Loon (Gavia immer) migration 2002-2008. By extrapolation we estimate
that up to 1046, 1529, 1693, 1193, 4933, 3650 and 1628 waterbirds may have perished.
The waterbird species with the greatest mortality differed for the 2000-02
mortality events. Redbreasted Merganser (Mergus serrator) had a predicted mortality
of 2479 in 2000, Common Loon 1149 during 2001, and Long-tailed Duck (Clangula
hyemalis) 13219 in 2002. Common Loon experienced the greatest mortality during the
2003-8 events, ranging from 1656 to 10040.
Allen, Jenica M*1; Ibáñez, Inés2, Wilson, Adam M1; Treanor, Sarah A1; Silander, John A1 – (1) University of Connecticut; (2) University of Michigan
Identifying hot spots of plant species invasions and assessing foci of further spread
Invasive species are a global ecological and economic issue, making inference on where
to target early control and eradication efforts critical. We aimed to forecast hotspots
of invasion in terms of invasive species richness and high abundance of particular
species by combining climate, land-use/land-cover (LULC), and habitat information in
spatially-explicit hierarchical Bayesian models. Species occurrence and abundance data
were derived from the Invasive Plant Atlas of New England (IPANE), demonstrating the
potential for fruitful collaborations between researchers, citizen scientists, and
resource managers. Species–specific analyses included prominent plant invaders in
New England: Berberis thunbergii (Japanese barberry), Celastrus orbiculatus (oriental
bittersweet), Elaeagnus umbellata (autumn olive), Euonymus alata (burning bush), and
Rosa multiflora (multiflora rose). Projections were made using two future climate
models (CCSM3 and UKMO-HadCM3) in addition to current climate.
Both the richness and abundance models indicate that climate variables were most
influential in determining the incidence or cover of invasives, followed by site and
LULC variables. Invasive species richness was higher in warmer areas with lower
annual and highly seasonally variable precipitation. Edge habitats increased and
evergreen forest and cropland LULC decreased invasive richness. The abundance
analysis showed differences in the direction and magnitude of the effect of each
predictive variable among the five species, demonstrating the need for both synthetic
and species-specific approaches to prediction and management. Model predictions
suggest that all species, except E.umbellata, may be more abundant relative to
current climate under moderate predictions (CCSM3), but that their incidence may be
reduced under extreme climate predictions (HadCM3).
Allstadt, Andrew*; O’Malley, L; Kozma, B; Korniss, G; Racz, Z; Caraco, T; Newman, J – University at Albany
Velocity and roughening of an invasive front
After establishment, many exotic species expand into the surrounding environment
through local propagation, spreading as a discernable invasive front. We model this
spatial advance as an individual-based, stochastic process in two dimensions, where an
invasive and a resident species compete preemptively for resources. Initially, the
species are separated by a linear front; the invader’s subsequent advance is governed by
local dispersal and mortality events in both species. At early times, correlations in the
position of leading invasive individuals develop over short distances. As the front
continues to advance, the length of these correlations grows until they extend over the
entire front. Velocity of the front and variance about the average front position grow
with correlation length, and reach their asymptotic values as the correlation length spans
the front. Consequently both asymptotic velocity and front variance exhibit specific
scaling relationships with the front length, regardless of the detailed propagation and
mortality processes. These relationships also suggest this ecological model belongs to
the Kardar-Parisi-Zhang (KPZ) universality class; a set of spatial-growth models sharing
common scaling properties. Other KPZ systems include the advance of wildfires, spatial
epidemic spread, and the Eden model of tumor growth. Given that ecological invasion with
local dispersal belongs to this universality class, we can specify the probability
distribution of the most advanced invader, the “front runner.” We shall test hypotheses
related to the length of an invasive front with a field experiment, using grass and clover
as a model system.
Averill, Kristine M*1; DiTommaso, Antonio1; Mohler, Charles L1; Milbrath, Lindsey R2 – (1) Cornell University; (2) USDA-ARS Robert W. Holley Center for Agriculture and Health
Generating biological data on the invasive swallow-worts (Vincetoxicum spp.) to better inform their management using biocontrol
Pale and black swallow-wort (Vincetoxicum rossicum and V. nigrum, respectively) are nonnative, perennial,
herbaceous vines in the Apocynaceae. The species are becoming increasingly problematic in the northeastern
United States and southeastern Canada and management of the species has been challenging. A classical
biological control program was initiated in 2004 by the USDA-ARS. Success of this biological control
effort depends on the availability of plant demographic data, which can be modeled to determine which
swallow-wort life stage(s) are likely to be most susceptible to control efforts. Since little is known
about the establishment phase of swallow-wort’s life cycle, we conducted a field experiment in central New
York State to determine establishment and survival during the first two years after sowing.
We sowed pale swallow-wort seeds in two old-fields subjected to four disturbance regimens. We
hypothesized that establishment and survival would be greater in treatments with greater disturbance.
At the better-drained site, overall swallow-wort establishment was 15(1)% and did not differ between
treatments. At the poorly-drained site, establishment varied by treatment; mowed and control plots had
greater swallow-wort establishment (10(2)%) than herbicide+tillage and herbicide plots (1.6(0.5)%). Of
emerging seedlings, survival was high at both sites (70–84%). At both sites, swallow-wort total (above-
and below-ground) biomass was greater in herbicide + tillage and herbicide plots than in mowed and control
plots. These results indicate that pale swallow-wort establishment and survival is successful across a
range of disturbance regimens and that growth is greater in more disturbed regimens. Biocontrol
implications will be discussed.
Chang, Cynthia*; Smith, Melinda – Yale University
Different levels of diversity have varying impacts on invasion resistance and productivity of tallgrass prairie
Native community diversity has historically been thought to play a central role in invasion resistance by increasing interspecific trait variation. Trait variation also occurs at the intraspecific level, where phenotypic and/or genotypic diversity could confer invasion resistance via the same mechanisms. Genotypic variation within a dominant species may account for overall phenotypic trait variation
within a given community, and thus may play a central role in determining invasion resistance. We conducted our study in 66 1-m2 plots located in intact tallgrass prairie. For each plot, we measured
the genotypic and corresponding phenotypic variation of dominant C4 grass individuals (Andropogon gerardii) and plant community diversity. Establishment and persistence of added invasive grass seeds (A.
bladhii) was monitored. Finally, we measured resource (nitrogen, water and light) availability. Multiple regression analyses found early-season soil moisture content and end of season individual biomass of the dominant species to be significantly related to invasion success (both early and late season). Genotype variation of A. gerardii was also significantly related to late season persistence
of the invasive grass. This suggests that both resource availability and genotypic variation within a dominant species are important drivers in invasion resistance. Furthermore, genotypic and phenotypic variation are positively correlated which suggests that phenotypic trait variation in a dominant species could be one key mechanism driving invasion resistance. Finally, community diversity was not found to be significantly related to invasion, suggesting that it is population level diversity of the dominant species that plays an
important role in tallgrass prairie under invasion.
Cohen, Jillian S*1; Maerz, John C2; Blossey, Bernd1 – (1) Cornell University; (2) University of Georgia
It’s not where you're from, it’s who you are that counts: Plant traits determine impacts on larval amphibians
Plant detritus is the primary energy source in freshwater benthic food webs. Theory
suggests that plant invasions can affect consumers by changing the quality of the detrital
pool, but empirical evidence for this is lacking. Tadpoles, a dominant wetland consumer,
may be particularly responsive to shifts in litter quality, as they feed largely on detrital
biofilms. I conducted two experiments to evaluate the impacts of invasive plant litter on
tadpoles. For each experiment, I hypothesized that litter quality, including C:N, C:P, N:P,
and phenolic content, would determine tadpole productivity. First, I conducted a field
experiment involving four native and five invasive plant species at five wetland complexes
in central New York. I installed field cages in sites dominated by a single species of each
plant and added three tadpole species according to their natural phenology. I monitored
cages regularly, collecting and weighing all metamorphosed individuals as they became
available. Importantly, my data shows that tadpole performance did not differ in habitats
dominated by native and invasive plants. Rather, my findings suggest that plant traits,
irrespective of plant origin, determine amphibian performance. For my second experiment,
I raised tadpoles in mesocosms containing litter from 15 populations of a single invasive
species that varied widely in litter quality. Similar to my first experiment, litter traits
explained much of the observed variation in tadpole productivity. These experiments show
that litter quality strongly influences tadpole performance and suggest that functional
traits, irrespective of species origin or identity, can have important consequences for
ecosystem function.
Collins, Rachel J*; Bankert, Christina A; Gibson, Zach M; Patel, Devki G; Smith, Adrienne M – Roanoke College
Facilitation or apparent facilitation? Patterns of invasive plant and exotic earthworm abundances in Southwestern Virginia
Non-native species pose serious threats to native communities and are a top cause for
species endangerment worldwide. Two important approaches to understanding these threats
include assessing (1) the causes of invasion, and (2) the effect of invasions. We used both
approaches in studying the effects of two invasive plant species (Asian Stilt grass
(Microstegium vimineum) and garlic mustard (Alliaria petiolata)) and exotic earthworm
communities in forest in Southwestern Virginia. We surveyed plant and earthworm communities
in eight forests in 2007 and 2008. These sites ranged from small suburban fragments (<10 ha)
to large nature reserves (5,100 ha). After two years of sampling, earthworm communities in
our study sites appear to be comprised solely of exotic species. We found positive
correlations between exotic earthworm richness and the abundances of exotic plant species
and vines (multiple regression; r2 = 0.97 ; P < 0.5; n = 7 ). Further, exotic plant species
richness was greater within areas of dense M. vimineum and A. petiolata populations compared
to areas without invasive plant species (two sample t-test; t = 2.69; P < 0.05; df = 19).
Lastly, we found a negative correlation between native plant species richness and invasive
plant species abundance (linear regression; r2 = 18.3, P < 0.05, N = 24). Taken together,
our results suggest that invasive plants and exotic earthworms may facilitate each other
similar to the Invasion Meltdown mechanism and our sites seem to exhibit Biotic Resistance
where high native species richness inhibits invasions.
Farrer, Emily C*; Goldberg, Deborah E – University of Michigan
Mechanisms and reversibility of effects of hybrid cattail on native wetlands
Most invasive plants negatively affect the native communities they invade. However,
invasives can affect natives via different mechanisms, and distinguishing among them is
essential for understanding the dynamics of invasions and for directing management
strategies. Two common mechanisms of invasive plant effect are direct competition and
alteration of the environment. We tested this in a Great Lakes marsh invaded by
Typha x glauca (hybrid cattail), which produces monodominant stands with considerable
litter accumulation. We teased apart the effects of live T. x glauca vs. its litter on
the environment and plant community with a live/litter transplant experiment. We also
tested whether these effects were reversible by a live/litter removal experiment in the
Typha stand. Over four years, both transplanted litter and live T. x glauca increased soil
inorganic nitrogen, but only litter decreased light. Litter had a much stronger effect on
the plant community, decreasing native diversity and abundance and changing community
composition to a more terrestrial species assemblage. Removal of litter and live
T. x glauca had no affect on soil nutrients, but litter removal greatly increased light.
Litter removal resulted in a greater increase in native diversity and abundance than removal
of live T. x glauca, however it did not restore native marsh species, but rather recruited
more terrestrial grasses and forbs. These results suggest that T. x glauca affects native
plants by altering the environment by litter accumulation; however removal of aboveground
litter will not restore wetland communities, because altered soil conditions favor
colonization by terrestrial plants.
Giencke, Lisa M*; Dovčiak, Martin; Mitchell, Myron J – SUNY College of Environmental Science and Forestry
Spatial dynamics and effects of beech bark disease on an Adirondack forest
American beech (Fagus grandifolia), a major forest tree species in the Northeastern U.S.,
has been increasingly infected throughout its range by beech bark disease (BBD), which is
caused by a non-native insect scale (Cryptococcus fagisuga) and fungal pathogens (non-native
Neonectria coccinea var. faginata or native N. galligena). Although BBD can considerably
affect forest ecosystem structure and function, our understanding of disease spatial
dynamics in infected stands and its effects on tree recruitment is rudimentary. We studied
spatial patterns of insect scale, canker and tree recruitment using historical stem maps
from a ~2 ha plot in a mature northern hardwood forest in the central Adirondacks. Species,
diameter at breast height (DBH) and spatial location of all trees (with DBH > 5 cm) in the
plot were recorded in 1985 and 2000. Percentage of each beech stem infected by scale and
canker was recorded in 2000. We analyzed spatial patterns of infected beech trees and tree
recruitment using Ripley’s K-function. Almost 80% of small beech trees (DBH < 10 cm) were
not infected by canker but about half were already attacked by scale in a spatially patchy
fashion. The majority of larger beech trees were attacked by scale and canker; attack
severity appeared correlated to distance from a heavily infested stand section. Despite
increased mortality, beech abundance increased from 1985 to 2000; dead beech trees were
positively associated with live beech recruits (but negatively with uncankered recruits).
Thus, BBD can lead to continuous presence of low quality beech stands.
Jiang, Hao; Zimmerer, Edward; Liu, Dongjiao; He, Kate* – Murray State University
Using molecular markers to study the patterns of genotypic diversity of an invasive plant, alligator weed (Alternanthera philoxeroides) in southeastern US
Alligator weed (Alternanthera philoxeroides) is a successful invader native to South
America. It has invaded all continents except Africa and Europe. In spite of its serious
invasiveness all over the globe, alligator weed has been rarely studied in terms of its
invasion mechanisms. It is even more surprising that knowledge on the relationships between
its genetic variation and invasiveness is still very limited. This project attempts to
uncover the mechanisms of alligator weed invasion using molecular markers to examine the
patterns of genotypic variation of this successful invader. The analysis of genetic
variation was carried out using Inter-Simple Sequence Repeat markers (ISSRs) on plant
samples collected from three states in the southeastern US. The molecular evidence indicates
that there is genetic variation in alligator weed populations. The results of this study
suggest that genetic variation is closely related to the history of species introduction.
Moreover, high genetic variation found in alligator weed populations contributes to its
invasion success.
Jones, Chad C* – Connecticut College
Habitat distribution models poorly predict future occurrences of two invasive species
Habitat distribution models are increasingly used to predict the potential distribution
of invasive species. If successful, these models can help managers target limited resources
for monitoring and controlling invasive species to areas where the species are most likely
to occur. The accuracy of these models is usually determined based on the current species
distribution. However, because invasive species are not at equilibrium with the environment,
models that accurately predict current distributions of invasive species may not be
effective at predicting future distributions. I used data on the 1982 distributions of two
invasive species, Celastrus orbiculatus and Rosa multiflora, in a natural area in
southeastern Connecticut to create habitat distribution models using logistic regression.
I then assessed how well these models predicted the distributions of the two species in
1982, 1992 and 2002. Overall model accuracy for Celastrus was high in 1982 and 1992 but
declined in 2002. In addition, the ability of models to accurately predict new occurrences
declined dramatically from 98% in 1982 to 76% in 1992 and only 27% in 2002. Models for Rosa
followed a similar trend although predictive accuracy only dropped from 92% in 1982 to 61%
in 2002. Both species have begun to invade types of habitats not invaded in 1982. These
results suggest that measures of model accuracy from the time that model is developed are
not good determinants of the ability of models to predict future occurrences. Thus habitat
distribution models for invasive species must be used with great care.
Knight, Kathleen S*; Long, Robert P; Rebbeck, Joanne; Herms, Daniel A; Cardina, John; Herms, Catherine P; Klooster, Wendy; Gandhi, Kamal JK; Smith, Annemarie; Costilow, Kyle; Long, Lawrence; Smith, Stephanie K; Cappaert, David L – US Forest Service, Northern Research Station
Effects of emerald ash borer (Agrilus planipennis) on forest ecosystems in North America
Emerald ash borer (EAB) (Agrilus planipennis), a recently introduced beetle, has killed
millions of ash (Fraxinus spp.) trees in North America. In over 250 monitoring plots in
forests in Ohio and Michigan, representing a gradient of EAB infestation duration, we are
monitoring the decline and mortality of thousands of ash trees, the responses of both native
and invasive plant species, changes in species composition and forest structure, and effects
on other organisms and ecosystem processes. The plots are located in forest stands of
different ages and in different habitats to include all five ash tree species native to the
region (F. Americana, F. pennsylvanica, F. nigra, F. profunda, and F. quadrangulata).
Mortality of mature ash trees in a forest stand may reach 98% within six years of infestation
by EAB, and is not affected by habitat or by the density, basal area, or species composition
of ash trees. Invasive plant species are present, but not dominant, in most plots, with
individual species distributions related to habitat, geography, and land use history. These
plants may increase in abundance due to canopy gaps that result from ash mortality. EAB may
dynamically interact with other species in these forest ecosystems. Woodpecker feeding
behavior changes as woodpeckers take advantage of the abundant food source that EAB
represents. Native parasitoid wasp species have been observed parasitizing EAB. We will
continue to monitor these changing forest ecosystems as the effects of EAB reverberate
through them.
Liu, Dongjiao*; Jiang, Hao; Zhang, Robin; He, Kate – Murray State University
Predicting the spatial distribution of an invasive plant, Lonicera japonica, based on species occurrence data from two watersheds in Western KY and TN
The invasion of alien plants has serious ecological and economic consequences. Geographic
factors including human disturbances and habitat characteristics such as land cover, terrain,
water and soils play an important role in plant invasion. However, the spatial distribution
of most invasive plants is poorly documented, the path of dissemination is sketchy and the
mechanism of spatial dispersal is mostly unclear. This project examines and compares the
spatial distribution of a successful invasive plant, Japanese honeysuckle (Lonicera japonica)
, in two watersheds of similar size but ecologically distinct in Western Kentucky (Ledbetter
Creek) and Western Tennessee (Panther Creek). The occurrence data of Japanese honeysuckle
and nine environmental variables were collected and measured from a total of 283 random
plots at the two watersheds. A spatial logistic regression model was developed to identify
the factors that contribute most to the spread of this invasive plant. Our results show
that the spatial distribution of this invasive plant appears to be different at the two
watersheds. The Ledbetter Creek watershed with heavier anthropogenic disturbances has a
greater distribution of Japanese honeysuckle than the forested Panther Creek Watershed.
The spatial regression model indicates that the distance from the main road, soil moisture,
light intensity, and plant species richness of each plot were significantly correlated
with the spatial distribution of invasive species at the Ledbetter Creek Watershed.
However, elevation was the only significant factors in relation to the spatial
distribution of Japanese honeysuckle at the Panther Creek Watershed. Furthermore, our
results suggest that the invasion risk is strongly linked to anthropogenic disturbances.
Molofsky, Jane*; Collins, A Robin – University of Vermont
Evolution of range margins in invasive species
The study of invasive species at their current range margin and beyond can provide
information on the likely distributional limits of the invasive species and its response to
changing climate. In this study, we planted individuals of the invasive grass Phalaris
arundinacea taken from its native range in Europe and its introduced range in the United
States into common gardens along a climatic gradient to determine whether individuals are
locally adapted to the current climate regime and whether they have the potential to evolve
with changing climate. Native genotypes collected from the center (Czech Republic) and
their range margin (France) and introduced genotypes collected from the center (Vermont) and
the current range margin (North Carolina) were grown in identical common gardens in Vermont,
North Carolina, Georgia and Florida. Survivorship declined sharply along this climatic
gradient with no individuals surviving in Florida; there were no significant differences in
survivorship between native and invasive genotypes. For tiller number and biomass, there
were few significant differences among populations in their mean performance within a single
garden; furthermore, there was no evidence for local adaptation of individuals to a
particular climatic region. In North Carolina, both the French and North Carolina genotypes
exhibited higher heritability for tiller number and biomass than the Czech Republic and
Vermont genotypes. Thus, genotypes from climatically similar regions had higher evolutionary
potential than those that came from climatically dissimilar regions. However, at the
climatic extremes of Vermont and Georgia, we found that invasive North Carolina genotypes
had significantly higher heritability than the native French genotypes.
Mooney, Emily H*; Morrissey, Danielle – Massachusetts College of Liberal Arts
Population variation in herbivory-related traits in Japanese knotweed, Fallopia japonica
Japanese knotweed, Fallopia japonica, is a non-native, invasive species throughout Europe and the United
States. Our research focused on understanding how herbivory-related traits vary among populations of
F. japonica. Plants were propagated from rhizomes obtained from three distinct populations. We used
Spodoptera exigua larvae in a bioassay to assess variation among these population sources. Larvae were
allowed to feed on plants for 72 hours, after which we measured the leaf area consumed by larvae and the
weight gain by larvae. In addition, we assessed plants response to herbivory by measuring chlorophyll fluorescence. While weight gain by the larvae did not vary among
population sources, there was evidence that response to herbivory varied among population sources.
Specifically, chlorophyll fluorescence increased following herbivory, but the extent of increase varied
among population sources. We are currently analyzing leaf area data, so that we can test for differences in
conversion efficiency among larvae feeding on plants from different populations sources.
O'Donnell, Kelly L*; Pigliucci, Massimo – Stony Brook University
Selection dynamics of native and invasive annual Polygonum species
The ability to evolve rapidly is often implicated in discussions of what makes
invasive plant species invasive. However, we are often lacking knowledge of which traits
are under selection during an invasion. Plant invasions represent natural experiments that
allow us to both explore the dynamics of natural selection in the wild and examine the
evolution of an invader on contemporary time scales. We conducted a study of 10 natural
populations of two invasive species (Persicaria lapathifolia and P. cespitosa) and one
native species (P. pensylvanica) to quantify the amount of natural selection acting on
these species to compare the selection dynamics to which each is exposed. We also conducted
a germination trial to compare the potential for invasion determined by germination rate.
A Lande-Arnold style multiple regression selection analysis was performed on five
morphological traits (height, stem diameter, leaf number, leaf shape, and leaf area) using
flower number as our fitness proxy. Most selection was indirect and caused by correlations
with other traits under selection. However, there was significant direct selection for
increased leaf number in both natives and invasives and thicker stems in just the invasives.
The germination test showed that not only do the invasive plants have a significantly higher
germination rate (>60% compared to 3%), but they also germinate significantly faster; both
findings have large implications for the ability of these two invasives to spread. Another
field season would need to be conducted to examine how each species is responding to their
set of selection pressures.
Pinder, Rebecca A1*; Groffman, Peter M2; Robinson, George R1 – (1) University at Albany; (2) Cary Institute of Ecosystem Studies
Streamside interactions between salamanders, earthworms and soil nitrogen cycle processes
In North American forests, exotic earthworms are expanding their ranges into forests that
were previously earthworm free. Earthworms can disrupt native forests by altering understory
plant composition, consuming large amounts of leaf litter, mixing soil layers, and altering
nutrient dynamics. The main objective of this study was to determine if quantity and
diversity of earthworms and salamanders along stream banks are associated with differences
in nitrogen cycling in these soils, focusing, in particular, on assessing the rates of
nitrification, mineralization and denitrification along the stream bank. Soil samples were
collected from stream banks in the Adirondack, Catskill and Helderberg regions of New York
State where salamander and earthworm abundances, level of co-occurrence, and diversity were
measured. Nitrification, mineralization and denitrification rates were compared across 16
streams. Potential denitrification rates were determined using a denitrification enzyme
assay, while potential nitrification and mineralization rates were determined using
laboratory incubations. There was a positive, though not significant, relationship between
denitrification potential and the number of earthworms encountered. There was no
significant relationship between nitrification and mineralization rates and abundances of
earthworms or salamanders. As some earthworm species are thought to exert more of an
effect on nitrogen cycle processes than others, further analysis will be done on a species
by species basis (1237 earthworms were collected for identification and 1138 salamanders
were identified to species in situ). Future work will focus on designing controlled
experiments to further examine how earthworms and salamander interactions affect nitrogen
cycling along the stream edge.
Rauschert, Emily*; Mortensen, David – The Pennsylvania State University
Quantifying the role of roads and road maintenance in the spread of an invasive plant, Microstegium vimineum
Preventing the spread of invasive species into new areas is seen as a critical for
management, as eradication is often difficult, if not impossible, once populations are
well established. The importance of human activity for the spread of invasive plants has
long been recognized, but quantification of the impact of the vectors involved is lacking.
We present a conceptual framework and ongoing experiments to understand the rapid spread of
the invasive exotic Microstegium vimineum (Japanese stiltgrass). Detailed small-scale
experiments provide the data to model the natural spread of Microstegium, which is several
orders of magnitude slower than actual large-scale observations. Spread in roadside habitats,
although variable, was found to be greater than in forested or wetland habitats. Forested
roads, along which Microstegium grows abundantly, are often unpaved and are subject to
frequent maintenance activities such as road grading. Experiments using seed proxies
document the potential of road grading to rapidly spread seeds throughout road networks.
We also investigate the role of road structures such as culverts in facilitating invasion
into the forest interior. These results highlight the need to limit human-mediated spread
when managing invasive species.
Rollinson, E*; Ness, JH – Skidmore College
Exotic plant species experience less herbivory than natives in a phylogenetically controlled survey
Enemy release is one mechanism by which exotic species may spread and become invasive.
The enemy release hypothesis proposes that introduced plant species leave co-evolved
natural enemies behind in their native ranges and, as a result, experience reduced
herbivory and pathogen loads in their introduced range. This reduction in natural
enemies may facilitate invasions of exotic plants if they experience lower levels of
herbivory than native plant species. We compared herbivory on native and exotic plant
species that naturally co-occur in riparian and forest habitats in Saratoga County, NY.
We monitored a total of 43 plant species (26 native and 17 exotic; average 9 ± 4
individuals per species) in 30 families. Differences in herbivory between exotic
and native species may be confounded by phylogenetic relationships among species in
either of these categories; using taxonomically paired exotic and native species
controls for these common ancestry effects. Therefore, we both directly compared
native and exotic species, and compared them within taxonomically controlled groups.
Exotic species had significantly lower levels of herbivory than did native species;
this result remained when only taxonomically-controlled groups of species were
compared. Our results suggest that observations of reduced herbivory in exotic
species is truly a result of their introduced status, rather than an artifact of any
common ancestry among exotic species. This enemy release may be an important mechanism
of biological invasions.
Rollinson, E; Ness, JH* – Skidmore College
Consequences of riparian invasion for in-stream food webs and litter processing
Small streams are often powered by energy and other resources delivered by senescing
leaves falling from riparian vegetation. We tested the hypothesis that invasions of
riparian zones by Japanese knotweed (Fallopia japonica) alter the development of
in-stream food webs. We used 0.1m2 buckets to collect dehiscing leaves along a transect
that included invaded and non-invaded riparian habitat abutting Kayaderosseras Creek, NY.
We weighed the leaves that fell weekly from 21 Sept to 25 Nov, 2008. Owing to
among-species differences in leaf-fall phenology (median loss prior to Oct 14 for
Populus, Acer, Rhamnus, Tilia and Ulmus spp, Oct 28 for Quercus spp and Nov 4 for
Fallopia), leaves in knotweed-invaded microsites entered streams later in the autumn.
We created leaf-packs that mimicked the changing composition of in-stream litter
derived from these two habitats, systematically adding leaf material to leaf packs and
collecting a sub-sample of the leaf-packs five times over a 40 day interval. We
demonstrated that litter from invaded microsites was processed more slowly over a
given time interval and also found differences in macro-invertebrate community
composition, with higher diversity and lower Plecoptera representation in the invaded
leaf-packs. We attribute these differences to the combined effects of differences in
leaf quality, leaf age, and progressively falling water temperatures when late autumn
leaves, such as knotweed, enter the stream.
Wildova, Radka*123; Goldberg, Deborah1 – (1) University of Michigan; (2) Institute of Botany, Academy of Sciences of the Czech Republic; (3) Ecological Research Institute
Exotic and native cattails and their hybrid in North America: Implications for understanding cattail invasions
We examined the ecology of invasions of northern Michigan wetlands by the European cattail, Typha
angustifolia, and its hybrid, T. x glauca, with native T. latifolia. Little is known about wetland
characteristics affecting invasibility, the mechanisms by which T. angustifolia or T. x glauca invades,
or whether either displaces T. latifolia. Surveys revealed T. angustifolia was more abundant in unshaded,
densely-vegetated wetlands on sandy soils, while T. latifolia was better represented at sites with exposed
organic soils, standing water, and tree shading. The hybrid was restricted to unshaded sites with fine
textured soils. However, all three parent taxa did have some habitat overlap. Two experiments revealed
responses to environmental conditions consistent with these patterns. In a common garden experiment, low
soil organic matter (SOM) decreased the growth of T. latifolia and the hybrid, but not that of
T. angustifolia. In contrast, low light decreased the growth of T. angustifolia and the hybrid, but not
of T. latifolia. The hybrid had higher growth than both parents only when both SOM and light were high.
However, in a four year field experiment in which all three taxa were transplanted to a marsh with sandy
soil, low SOM and high light, both survival and productivity of the hybrid were consistently higher than
both parents despite these oligotrophic conditions. Our results suggest differing growth responses to soil
texture, organic matter, and light can enable invasion by both the non-native and hybrid taxa into wetland
habitats that would be unoccupied by the native species, and that degree of eutrophication is not the key
variable triggering invasion.