Evaluation of Miscanthus Cultivars for Fecundity and Potential ...

Can cultivars of invasive plants be
safe? Examples from Miscanthus
Kayri Havens and Glen Madeja
Chicago Botanic Garden
and
Tiffany Knight
Washington University

The Invasive Problem
• Invasive species are the 2 nd
largest threat to biodiversity
• We depend on biodiversity
• Food, Medicines
• Shelter
• Ecosystem services
• Invasive species cost the US
$138 billion/year, invasive
plant costs are conservatively
$35 billion/year

The “Cultivar Issue”
• Cultivars can vary
significantly in their
fecundity
• When a wild type and/or
one or more cultivars are
invasive, should all be
banned?
• Are “sterile” cultivars
always sterile?

Modeling effect of fecundity on
population growth rate
• We took a demographic approach to
ask, “When reducing fecundity of
cultivars, how much is enough to create
a plant that will not be invasive?”
• Modeling was done by Tiffany Knight
(Washington University)

Japanese Barberry (Berberis thunbergii)
A popular horticultural shrub that has become a natural area invader
“The reasons? Sheer growability… hardy
to zone 4, can take sun or shade, wet or
dry, and will come back strong after a
beating.”
“one of the most destructive invasive plants in Connecticut”
--Connecticut Botanical Society

Why the resistance?
Japanese Barberry sales in Connecticut Alone
--$15-20 million Annually--

Why the resistance?
35 Cultivars of Japanese Barberry
• Aurea
• Bonanza Gold
• Angel Wings
• Crimson Giant
• Rosy Glow
Individuals within these range from producing less than
100 to over 3000 seeds per year
“I know that some Barberries have become invasive but
mine doesn't really set any seed and my plants are
only 2 feet high after almost 5 years in the ground.”

A demographic approach
Cultivar #1
Cultivar #2
0.05
0.95
0.50
0.95
Seedling
0.05
Juvenile
0.80
Adult
Seedling
0.05
Juvenile
0.35
Adult
1000 * 0.10
50 * 0.10
λ=1.50
λ=1.00

Plant invasions and matrix models
Plant
Life form
Invasive Range Selected Reference
Dipsacus sylvestris Biennial USA Werner and Caswell 1978
Alliaria petiolata Biennial USA Davis et al. 2006
Carduus nutans Monocarpic herb New Zealand Shea and Kelly 1998
Heracleum mantegazzianum Monocarpic herb Europe Nehrbass et al. 2006
Cirsium vulgare Monocarpic herb USA Tenhumberg et al. 2007
Molinia caerulea Perennial grass Western Europe Jacquemyn et al. 2005
Agropyron cristatum Perennial grass USA Hansen and Wilson 2006
Lespedeza cuneata Perennial herb USA Schutzenhofer and Knight 2007
Centaurea maculosa Perennial herb USA Emery and Gross 2005
Clidemia hirta Shrub USA DeWalt 2006
Ardisia elliptica Shrub USA Koop and Horvitz 2005
Cytisus scoparius Shrub USA Parker 2000
Pinus nigra Tree New Zealand Buckley et al. 2005

Alliaria petiolata (Garlic mustard)
A typical short-lived invasive plant
Seed
Rosette
Adult
Seed
Bank
Rosette
Adults
Davis et al. 2006

Alliaria petiolata (Garlic mustard)
A typical short-lived invasive plant
Seed
Rosette
Adult
0.02
0.27
Seed
Bank
.026
0.36
0.03 0.62
Rosette
0.09 0.45
.27
Adults
λ=1.42
0.09
Davis et al. 2006

Population growth rate (λ)
Reducing seed output reduces population
growth of garlic mustard
2.5
2.0
1.5
a
1.0
0.5
a
a
a
a
a
a
a
a
a
a
0
0 20 40 60 80 100
Percent reduction in seed production or viability

Population growth rate (λ)
Short-lived invasive species
2.5
d
e d
e
2.0
ca
ca
1.5 ci p
s
a
ci p
a s
d
e
ca
ci p
a
s
1.0
0.5
d
d
d
e
d
e
d
ca e
ci
d
p ca
a
ci e
a
p ca ci
p
d
a ci e
ca p
a ci e
ca a
p
ci
s
p
ca
a
e
ci p
a
s
ca
s
a d
ci
s
0
s s s ca
0 20 40 60 80 100
Percent reduction in seed production or viability
e p
Species
a Alliaria petiolata
ca Carduus nutans
ci Cirsium vulgare
d Dipsacus sylvestris
e Echium plantagineum
p Polygonum perfoliatum
s Setaria faberi

So, reduced seed output is likely to reduce
population growth of short-lived species….
…..But, what about long-lived species such
as shrubs and trees?

Scotch Broom (Cytisus scoparius)

Cytisus scoparius (Scotch Broom)
422
97.5
0.32
0.03
0.37
0.60
0.23 0.02 0.21
0.01 0.35
0.01
0.39
0.05
0.46
0.37
0.11
0.01
0.03
0.03
0.49
861
0.01
2725
0.44
0.11
0.85
λ=1.40
Parker 2000

Population growth rate (λ)
Reducing seed output has minor
effects on scotch broom
2.5
2.0
1.5
cy cy cy cy cy cy cy cy cy
1.0
cy
cy
0.5
0
0 20 40 60 80 100
Percent reduction in seed production or viability

Population growth rate (λ)
Long-lived invasive species
2.5
2.0 p
m
p p
m p
m p
cl cl m
p
cl m
p
cl m
p
cl m
p
cl
1.5
cl m p
cy cl m
ce cy
ce
cy cy
ce
cy cl m
ce
cy cy
a a a a
ce cy cl
r r r r a r ce
cy
a r ce a r
ce
a r a r cy r
a
r
1.0
ce m a cl p
ce cy
ce
Species
a Ardesia elliptica
ce Centaurea maculosa
cl Clidemia hirta
cy Cytisus scoparius
m Molina caerulea
p Pinus nigra
r Rubus discolor
0.5
0
0 20 40 60 80 100
Percent reduction in seed production or viability

Population growth rate (λ)
Population growth rate (λ)
Reducing seed output has larger effects on the
growth rate of short-lived species
2.5
2.0
1.5
1.0
0.5
0
Short-lived species
d e d
e d
d
e d
ca e
d
ca d
ci p ca e
s
d
a ci p ca e
a s ci p
a ci
d
ca
a
p ci e
a p ca ci
s
p a e d
ca p
ci
a ci e
ca a
p ci
s
p
ca a
e
ci p
a
e p
s
ca
s
a d
ci
s
s s s ca
0 20 40 60 80 100
2.5
Long-lived species
2.0 p
m p
m
p p
cl m p
cl m
p
cl m p
cl m
p
cl cl m p
1.5
cl m p
m
ce
cy
ce
cy cy
cl
ce
cy cy cl m
a ce r a r cy
a r a r cy ce cy cl
a r ce a r ce a r cy
ce
a r a r a
cy
1.0
r ce m
r
a cl p
ce cy
ce
0.5
0
0 20 40 60 80 100
Percent reduction in seed production or viability

Conclusions from models
Reductions in seed output will not necessarily
result in non-invasive cultivars, particular for
long-lived species
Demographic modeling can illuminate the
invasive potential of different cultivars if you
have the data
-seed output, seed viability
-life history (time to reproduction)
Knight, Havens and Vitt, 2011, BioScience 61: 816-822

Evaluation of Miscanthus sinensis
cultivars
• A long lived perennial grass that forms large
clumps (doesn’t run like M. sacchariflorus)
• Known to invade in eastern U.S.
• Fecundity will need to be zero (or extremely
close to zero) in order for the cultivar to be
unlikely to invade
• Glen Madeja (NU grad student) evaluated 35
cultivars for fecundity in the Chicago region
(Madeja et al., 2012, J Env Hort, in press)

Miscanthus trials
Glen taking data >
Tiffany with ‘Morning Light’ >

Quantifying seed set
• Randomly harvested 3
infloresences per individual
• X-rayed inflorescences
• 2 people independently
counted filled seeds and
averaged
• Multiplied by number of
inflorescences on individual
• Averaged filled seed set over
4 individuals per cultivar

Cultivar
Average Filled
Seed Set
Cultivar
Average Filled
Seed Set
Kleine Silberspinne 191,202 Ferner Osten 9,190
Rotsilber 179,957 Goliath 7,137
Autumn Light 157,936 Sarabande 3,278
Malepartus 106,172 Gracillimus 3,146
Blutenwunder 91,569 Little Zebra 1,359
Graziella 90,984 Superstripe 1,226
Nippon 81,024 Gold Bar 1,031
Huron Sunrise 77,925 Morning Light 968
Minuett 69,997 Strictus 907
Andante 61,103 Dixieland 785
Silberfeder 49,060 M. sacchariflorus 746, but runs!
Adagio 27,078 Variegatus 211
Puenktchen 19,376 Yaku-jima 138
Silberturm 19,133 Hinjo 0
Zebrinus 16,621 Silberpfeil 0
Purpurascens 13,390 M. x giganteus 0
Autumn Red 12,995 Cabaret 0, but died out

Conclusions
• Three ornamental cultivars (‘Silberpfiel’, ‘Hinjo’ and
‘Cabaret’) of Miscanthus sinensis and the hybrid
Miscanthus x. giganteus (used ornamentally and as a
potential biofuel crop) have not set seed in Chicago and
thus appear to have a low invasion risk.
• ‘Cabaret’ was not reliably hardy, so was not
recommended.
• These results should be interpreted with caution because
it is possible they may be able to set seed as the plants
mature and/or as the climate warms. These cultivars
may be able to mature seed in warmer regions of the
US. One of our seedless cultivars (‘Hinjo’) did set seed
in Zone 5 in another trial.

Acknowledgements:
• Thanks to the staff of the
Division of Plant Science
and Conservation and
collaborators on these
projects who shared data
and photos for this talk:
Pati Vitt, Glen Madeja,
Tiffany Knight, Lauren
Umek.