Historical Introduction Routes
of Invasive Plants to
Pennsylvania
Sarah Brown
Faculty Advisor: Cory Shoemaker, PhD

Issues with Invasives
• Introduction causes or is likely to cause
economic or environmental harm or harm to
human health
• Are the cause of 18% of endangered and
threatened species, have contributed to the
decline of 42%
• Harms agricultural productivity, public utility
operations, outdoor recreation, and property
values.
• $1.288 Trillion globally over the past 50 years

This Photo by Unknown Author is licensed under CC BY

Historical Invasion Routes

• Identifying introduction origins
• Conducive Habitats
• Vegetation morphology

Efforts Against Invasives
• Lack of established protocols
• Biological controls- chemical, mechanical,
biotic
• Monitoring efforts
• 1990- Invasives deemed a significant
component of environmental changes

Purpose
• Determine spread of invasive
species
• Reduce future invasions
• Identify possible advantages of
morphology
• Education
• <40% of PA consumers know
their plants are invasive

Elaeangnus
Umbellate
Autumn Olive

Pyrus calleryana
Bradford Pear

Vinca minor
Periwinkle

Hemerocallis fulva
Orange Daylily

Model Species
• Vegetation forms
• Horticultural status
• 174-23 samples
Hedera helix
English Ivy

Pueraria montana
Kudzu

Material and Methods
• Southeast Regional Network of Expertise and
Collections (SERNEC).
• 233 herbaria spanning 200 years
• 475 species
• Organization & Habitats
• Esri: GIS mapping software
• Callery pear, Bradford cultivar &
Montgomery county

Herbarium Records Pre-1850

Herbarium Records 1850-1875

Herbarium Records 1876-1900

Herbarium Records 1900-1926

Herbarium Records 1926-1950

Herbarium Records 1951-1975

Herbarium Records 1976-2000

Herbarium Records 2001-Present

Results

Historical Routes of Invasion
300

• 257 Human developed
• 101 Late successional
• 75 Early successional
• 42 Riparian zones
• Periwinkle vs Autumn Olive
• Orange daylily and Periwinkle

250

200

150

100

50

0
Human Developed

Riparian Zones

Early Successional

Late Successional

Error Sources & Future Endeavors
• Collector dispersal
• Accuracy of GPS
• Hydrogeological factors
• Source from other herbariums
• How are they spreading away
from human developed areas

Conclusions
• Human development
• What does this mean for the future?
• Box stores/ Conscious consumer/ Educate others.

References
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Gagliardi, James A., and Mark H. Brand. “Connecticut Nursery and Landscape Industry
Preferences for Solutions to the Sale and Use of Invasive Plants.” HortTechnology, vol. 17, no. 1,
2007, pp. 39–45., doi:10.21273/horttech.17.1.39.
Kelley, Kathleen M., et al. “Invasive Plant Species: Results of a Consumer Awareness,
Knowledge, and Expectations Survey Conducted in Pennsylvania.” Journal of Environmental
Horticulture, vol. 24, no. 1, 2006, pp. 53–58., doi:10.24266/0738-2898-24.1.53.
Pisula, Nikki L., and Scott J. Meiners. “Relative Allelopathic Potential of Invasive Plant Species in
a Young Disturbed Woodland1.” The Journal of the Torrey Botanical Society, vol. 137,
no. 1, 2010, pp. 81–87., doi:10.3159/09-ra-040.1.
Seastedt, Timothy R. “Biological Control of Invasive Plant Species: a Reassessment for The
A. New Phytologist, vol. 205, no. 2, 2014, pp. 490–502.,
doi:10.1111/nph.13065.
“U.S. Forest Service.” Forest Service Shield, www.fs.fed.us/wildflowers/invasives/.