Invasive plants show
more plasticity than
native plants
Irene Weber
University of Washington
HHMI Integrative Research Internship
What is an invasive plant?
Invasive plants are introduced species
that can thrive in areas beyond their
natural range of dispersal. These
plants are characteristically adaptable,
aggressive, and have a high
reproductive capacity.
USDA National Invasive Species Information Center
Why do we care about invasive plants?
Why do some plants invade?
• Ability to reproduce sexually
and asexually
• Rapid growth
• High tolerance of
heterogeneity
• Predator release
• Phenotypic plasticity in
changing environments
Baker 1965 Sakeital 2001
What is Plasticity?
Plant showing plasticity
Poor plasticity
Full sun conditions
Shade conditions
Plasticity in Invasive Species
Rumex acetosella
Invasive Species
vs.
Rumex venosus
Non Invasive Species
Stomatal Index
SI=((number of stomata)/(total cells: stomata + epidermal)) x 100
((6)/(6+34))x100 = 15
Methods
Hypotheses
Pre-industrial stomatal index
Invasive
Native
Stomatal index today
Results
21
Rumex venosus
19
y = -0.0208x + 55.504
R2 = 0.1351
Stomatal Index
17
15
13
11
9
Rumex acetosella
y = -0.0264x + 63.985
R2 = 0.2013
7
5
1880
1900
1920
1940
1960
Year plant collected
1980
2000
Stomatal Index% Decrease
100
80
60
40
20
0
Invasive Species
Native Species
Rumex acetosella
Rumex venosus
22% SI decrease
14% SI decrease
Conclusions
• The invasive plant shows a greater
overall change in stomatal index than
the native
• The invasive plant had a greater rate
of change than the native plant
Discussion
• This shows a difference in the way
that these two species respond in
correlation with CO2 increases in the
atmosphere
• This is evidence for the plasticity
theory of invasive species
Future Directions
• Does this trend hold up for other
plants?
• Is this purely due to plasticity or is there
a microevolution effect?
Acknowledgements
University of Washington HHMI Integrative Research Internship
Janneke Hille Ris Lambers, UW Department of Biology
Soo-Hyung Kim and Nicole Hackman, UW College of Forest Resources
UW Herbarium and the OSU Herbarium
Questions?