Download Horticulture, a Key Source of Introducing Exotic Species to Native

CHRYSALIS: The Murray State University Journal of Undergraduate Research
ABSTRACT
Back, l-r: Jacqueline Hawes, Sara Struve,
Erica Ludtke; front, l-r: Sanda Thomason,
Nicole Zelesnikar; not pictured: Laura Gossett
and Jami Kara Hitch
Laura Gossett
Jacqueline Hawes
Jami Kara Hitch
Erica Ludtke
Sara Struve
Sanda Thomason
Nicole Zelesnikar
As biology majors taking Bio116
in the Fall of 2006, we carried out a
study on species taxonomic affinity
and their native origins using nursery
plants. Studies have determined that
invasive species can have negative
effects on our natural ecosystems,
and most invasive species are
introduced intentionally through
nurseries. We hope that our research
project could help increase society’s
awareness of biological invasion and
the significance of native ecosystem
conservation.
Horticulture, a Key Source of
Introducing Exotic Species into
Native Communities
Studies have shown that invasive species can have negative effects on
natural ecosystems. Currently, there is a lack of specific information
on exotic and invasive plants in the state of Kentucky. This project was
designed to gather information on plant species found in local nurseries
in western Kentucky and to test the following hypotheses: there is no
relationship between species taxonomic affinity and native origin; and
there is no origin preference by people when purchasing gardening plants.
By identifying all species found in the local nurseries, we discovered a
significant relationship between taxonomic affinity and the origin of plant
species; and exotic plant species, especially of eastern Asia origins are
preferred by gardeners in general. We concluded that species taxonomic
affinity and native origin could be used as an effective indicator in
identifying the pool of potentially invasive species in the future. This
project could help increase society’s awareness of biological invasion
and the significance of native ecosystem conservation.
FACULTY MENTOR
Kate S. He is an assistant professor in the Department of Biological Sciences. She received her Ph.D.
from University of Western Ontario. Her research interests are in the broad areas of plant ecology with
emphasis on statistical analysis of patterns and processes of plant communities in time and space.
Her current research is centered on the study of the impact of invasive species on native ecosystems.
She teaches courses in Botany, Quantitative Ecology, and Introductory Biology. She also mentors
undergraduate students in her research laboratory.
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CHRYSALIS: The Murray State University Journal of Undergraduate Research
Horticulture, a Key Source of Introducing Exotic
Species to Native Communities and Ecosystems
E
xotic plant species are also called alien plants, non-indigenous
plants, and introduced plants in the literature. According to
Pysek et al. (2004), exotic plants are defined as plant species in a
given area whose presence is due to intentional or unintentional
human involvement. Without direct human intervention, some
of the non-native species are capable of independent growth and
sustain self-replacing populations for at least ten years. Such plants
We decided to study plants in our local nurseries. As the literature
suggests, a substantial number of plant species, especially woody
plants, have been intentionally introduced into new locations
through nurseries and botanical gardens (Reichard and White
2001). Furthermore, by collecting data at local nurseries, we can
evaluate customers’ preference for native versus exotic species.
Our null hypotheses were that there is no relationship between
are categorized as naturalized plants. Among the naturalized plant
species, about 10% or less could become invasive in the introduced
habitats (Williamson, 1996). Here ‘invasive’ means that plants
produce reproductive offspring, often in very large numbers, and
thus have the potential to spread over a large area (Pysek et al.,
2004).
species taxonomic affinity and origin and that there is no origin
preference by people when they purchase gardening plants from
local nurseries.
The impact of invasive plants has been observed in major natural
ecosystems (Baskin 2002). Typically, plant invasion can change
the niches of native species in the communities, alter the structure
and function of ecosystems, and disrupt the evolutionary processes
(D’Antonio and Vitousek, 1992; Williamson, 1996; Mack et al.,
2000). According to Pimentel et al. (2000), it is estimated that in the
United States alone more than 137 billion dollars is spent annually
on combating biological invasions. Thus, the study of invasive
species and their impact on the native ecosystems has emerged as
one of the crucial areas of biological research.
In the state of Kentucky, plant invasion has become one of the
critical tasks for conservation management. About 90 invasive plant
species have been listed by the Kentucky - EPPC (Southeast Exotic
Pest Plant Council, 2000). However, there is lack of a systematic
research on exotic and invasive plants in the state, especially in
the areas of the species origin and the mechanisms of species
introduction. This project was designed to gather information on
plant species found in local nurseries in western Kentucky to: (1)
identify species origin; (2) study species taxonomic affinity, i.e.,
to determine plant family, and (3) determine if relationship exists
between species taxonomic affinities and their native origin.
Methods
To test our hypotheses, we collected plant data from four local
nurseries in the vicinity of Murray, Kentucky. The nurseries
included Wal-Mart, Lowes, Rolling Hills, and the Wyatt Farms.
Each plant species found in the nurseries was recorded and
identified to species level. Taxonomic affinity was also examined
at the family level for each plant. The independent variable, native
origin was identified for all 124 exotic species. The dependent
variable, total number of plants per family, was determined and
recorded. StatView software was used to perform chi-square
analysis to determine whether or not the null hypotheses were
supported.
Results
There was a total of 183 plant species found in the four local
nurseries. The total number of native species proved to be much
lower than the number of exotic species. There were fifty-nine
(32%) native plants while there were one hundred and twenty-four
(68%) exotic species (Figure 1). Information on species native
origin is shown in Figure 2. The native origins of the plants are
identified as seven main geographical areas around the world, which
included Europe, eastern Asia, Africa, United States, India, Central
and South America, and the Australia/Pacific area. By percentage,
the largest groups of plants came from eastern Asia and the smallest
percentage came from the Australia/Pacific area.
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CHRYSALIS: The Murray State University Journal of Undergraduate Research
Number of species
160
7% Central and South America
4% India
120
2% Australia/Pacific area
16% Europe
5% Africa
80
40
0
Native
Exotic
32% United States
34% East Asia
Species Origin
Figure 1. Total number of exotic and native plant species found
at four Murray nurseries.
Table 1
Top eight families with most native species.
Family Name
Number of species
Violaceae
9
Cupressaceae
8
Hydrangeaceae
7
Pinaceae
6
Rosaceae
4
Ericaceae
4
Juncaceae
3
Cactaceae
2
Table 2
Top eight families with most exotic species.
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Family Name
Number of species
Cupressaceae
11
Araceae
9
Aquifoliaceae
8
Lythraceae
7
Laminaceae
7
Asteraceae
7
Brassicaceae
7
Rosaceae
6
Figure 2. Information of native origin of plant species found at
four Murray nurseries.
As shown in Table 1, our results indicated that the Violet family
(Violaceae) had the most number of native plants with a total of
nine species; and the Cypress family (Cupressaceae) obtained the
highest number of exotic plant species with eleven (see Table 2).
The results of chi-square analyses revealed: (1) there is a significant
relationship between taxonomic affinity and the origin of plant
species (p< 0.0001) and (2) exotic plant species are preferred by
gardeners in general (x2 = 23.08 > x2 a = 0.05, df =1 = 3.841).
Discussion
The results of our research show there were more than twice as
many exotic than native plants found in the local nurseries primarily
due to human preferences on gardening species. This finding is
consistent with other research studies. Nurseries have been one of
the major sources by which exotic plants are introduced into natural
communities (Reichard and White, 2001). Among the exotic species
found in Kentucky, a few have made negative impacts on native
ecosystems by endangering and replacing native species, resulting
in a loss of biodiversity. Typical invasive plants found in the local
area are Japanese honeysuckle (Lonicera japonica), Chinese privet
(Liqustrum sinense), oriental bittersweet (Celastrus orbiculata),
multiflora rose (Rosa multiflora), and tree of heaven (Ailanthus
altissima). Unfortunately, some of these species are still sold in
the local nurseries. Therefore, it is important to increase society’s
awareness of biological invasion due to its negative impact on
our native ecosystems. It is even more critical to have informed
and educated nursery staff and gardeners, so that invasive exotic
species will not be introduced and purchased at the nurseries in
the first place.
CHRYSALIS: The Murray State University Journal of Undergraduate Research
Our study also pointed out that a significant relationship between
taxonomic affinity and the origin of plant species does exist. Certain
families contain more exotic species than others, thus, taxonomic
affinity could be used as an effective indicator in identifying and
predicting potentially invasive species in the future. Information
on the native origin of species can also serve this purpose.
Although this research was very narrow in its scope, it could
provide a solid basis for further study on agricultural, ecological,
aquacultural, conservational, and commercial effects of exotic
plants in this area. Identifying potentially harmful species
presents a major challenge for scientists and is an essential step
in preventing invasion from exotic plants. Further research is
needed to determine if any of these species could present any
danger to local ecosystems. Additional statistical analyses should
also be performed to determine the probability that any of these
exotic plants are harmful. At the same time, increasing society’s
awareness of biological invasion should be treated as one of the
most important elements in the management and conservation of
our native ecosystems.
Mack, R.N., Simberloff, D., Lonsdale, W.M., Evans, H., Clout, M.
and Bazzaz, F.A. 2000. Biotic invasions: causes, epidemiology,
global consequences, and control. Ecological Applications
10: 689-710.
Pimentel, D., Lach, L., Zuniga, R., and Morrison, D. 2000.
Environmental and economic costs of nonindigenous species
in the United States. BioScience 50: 53-65.
Pysek, P., Richardson, D.M., Rejmanek, M., Grady, L., Webster,
L. and Williamson, M. 2004. Alien plants in checklists and
floras: toward better communication between taxonomists and
ecologists. Taxon 53(1):131-143.
Reichard S H. and White P. 2001. Horticulture as a pathway of
invasive plant introductions in the United States. Bioscience
51(2): 103-113.
Williamson, M.H.1996. Biological Invasions. Chapman and Hall,
London.
References
Baskin, Y. 2002. A Plague of Rate and Rubbervines: The Growing
Threat of Species Invasion. Island Press. Washington, DC.
D’Antonio, C.M. and Vitousek, P.M.1992. Biological invasions by
exotic grasses, the grass/fire cycle and global change. Annual
Review of Ecology and Systematics 23:63-87.
KY – EPPC, 2000. Invasive exotic plant list. http://www.se-eppc.
org/ky/list.htm
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