Jianqing Ding, Wei Huang and Yi Wang Invasion Biology and Biocontrol …jianqing-novel_biotec... ·...
Transcript of Jianqing Ding, Wei Huang and Yi Wang Invasion Biology and Biocontrol …jianqing-novel_biotec... ·...
Novel biotic interactions between invasive plants and herbiviores: implications for biological
control
Jianqing Ding, Wei Huang and Yi Wang
Invasion Biology and Biocontrol Lab,
Wuhan Botanical Garden/Wuhan Botanical Institute, Chinese Academy of Sciences
In collaborations withEvan Siemann, Juli Carrillo, Department of Ecology and Evolutionary Biology, Rice University
Greg Wheeler, Invasive Plant Research Laboratory, United States Department of Agriculture, Agricultural Research Service,
Jianwen Zou, College of Resources and Environmental Sciences, Nanjing Agricultural University
• Introduced insects establish populations well, impact is not sufficient
• Need to improve our ability to predict control efficacy prior to release
• Biotic and abiotic factors affecting interactions between invasive plants and herbivores
Why low success rate?
• “Enemy release” hypothesis (Elton 1958, Maron and Vila 2001) : exotic plants escaped suppression from natural enemies in their native range
• Insect communities: Native range: specialist and generalist herbivores Invaded range: only generalist, less or no specialist herbivores
Biological invasions: novel biotic interaction
• Evolved increased competitive ability (EICA) hypothesis (Blossey and Nötzold, 1995): exotic plants to reallocate their resources from defense against natural enemies to growth and reproduction
• Defense (due to differing insect community) Changes in resistanceplant trait that reduces the preference or performance
of herbivores Changes in toleranceplant ability to withstand and survive herbivore damage
(compensatory re-growth)
Altered selection in introduced range
• “plants that have evolved increased vigor in the exotic range will experience a particularly fast population build-up of biological control agents.” due to decreased defense
• the impact of insect agents on plant performance “will depend on the levels of resistance and tolerance evolved during the invasion process in the absence of specialist herbivores.”
Based on EICAMüller-Schärer et al. (TREE, 2004) predicted:
1 why a high abundance of some insect biological control agents has been found on invasive populations relative to their abundance in the native range
2 why these high number of insects failed to control the invader
those theories rarely tested in biocontrol programs.
Answers to questions
Case study: Chinese tallow Triadica sebifera
Native to China
Invasive in Southern and Southeastern US
Evolution in invasive Triadica
• Vigor growth• High competitive ability• Increased tolerance to herbivory• Less resistant(Siemann and Rogers 2001, 2003a, b, Siemann et al. 2006;
Rogers and Siemann 2004, 2005, Zou et al. 2008a, b )
(1) Do specialists consume and digest more food oninvasive populations than on native populations?Do generalists show the opposite pattern?(resistance)
(2) Does the plant show different compensatoryresponse to herbivory by specialists andgeneralists? (tolerance)
Questions: plant defense to generalist vs. specialists
Question 1: Resistance
Lab and field common garden tests: generalist andspecialist caterpillar
development of larvae reared on invasive/native plantleaves;
leaf biomass/areas consumed; leaf tannin and otherchemicals content
Experimental design
SpecialistGeneralist
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%X
OK
FL
ALGA
AR
LA
NCTN
MSSC
TX
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Anhui
Zhejiang
Jiangsu
Fujian
Jiangxi
GuangdongGuangxi
Hunan
Hubei
Henan
Guizhou
Taiwan Six populations from China
Six populations from US
(After Evan Siemann)
Results: plant resistance
0
0.1
0.2
0.3
0.4
0.5
Generalist Specialist
Las
t ins
tar
larv
al b
iom
ass (
g) InvasiveNative
n.s.
﹡﹡
﹡
A
C
﹡
Results: plant resistance
0
5
10
15
20
25
30
Generalist Specialist
Lar
val g
row
th r
ate
(mg/
d)n.s.
﹡0
0.1
0.2
0.3
0.4
0.5
Generalist Specialist
Las
t ins
tar
larv
al b
iom
ass (
g) InvasiveNative
n.s.
﹡﹡
﹡
A
C
﹡
Results: plant resistance
n.s.
0
5
10
15
20
25
30
Generalist SpecialistL
eaf m
ass c
onsu
med
(mg/
d)
n.s.
﹡0
5
10
15
20
25
30
Generalist Specialist
Lar
val g
row
th r
ate
(mg/
d)n.s.
﹡0
0.1
0.2
0.3
0.4
0.5
Generalist Specialist
Las
t ins
tar
larv
al b
iom
ass (
g) InvasiveNative
n.s.
﹡﹡
﹡
A
C
﹡
Results: plant resistance
n.s.
0
5
10
15
20
25
30
Generalist SpecialistL
eaf m
ass c
onsu
med
(mg/
d)
n.s.
﹡0
5
10
15
20
25
30
Generalist Specialist
Lar
val g
row
th r
ate
(mg/
d)n.s.
﹡0
0.1
0.2
0.3
0.4
0.5
Generalist Specialist
Las
t ins
tar
larv
al b
iom
ass (
g) InvasiveNative
n.s.
﹡﹡
﹡
A
C
﹡
Invasive low resistance to specialist; no difference for generalist
(Journal of Ecology, 2010)
0
2
4
6
8
10
12
14
1 2 3 4
Tann
in co
nten
t (m
g / g
DW
)
Seedlings age (Year)
InvasiveNative *
***
*
Results: secondary chemistry
High tannin content in invasive populations(Journal of Ecology, 2010)
Question 2: ToleranceField common garden tests: generalist and specialistcaterpillar
place larvae on invasive/native plant seedlings for 10 days;
plant re-grow after herbivory for 100 days
plant growth
Experimental design
Results: plant tolerance
0
8
16
24
32
40
No-herbivory Herbivory
Tot
al b
iom
ass (
g)InvasiveNative
0
30
60
90
120
150
No-herbivory Herbivory
Stem
hei
ght (
cm)
B
a
c
aa
ab
b b
Generalist
Generalist
c
Results: plant tolerance
0
8
16
24
32
40
No-herbivory Herbivory
Tot
al b
iom
ass (
g)InvasiveNative
0
30
60
90
120
150
No-herbivory Herbivory
Stem
hei
ght (
cm)
0
30
60
90
120
150
No-herbivory Herbivory
Stem
hei
ght (
cm)
0
8
16
24
32
40
No-herbivory Herbivory
Tot
al b
iom
ass (
g)
a bc
a
c d
aa
ab
b b
bc
ba
Generalist Specialist
Generalist Specialist
Invasive plants bigger than natives(Journal of Ecology, 2010)
Results: plant tolerance
Generalist Specialist
c
0
0.2
0.4
0.6
0.8
1T
oler
ance
scor
e
Generalist Specialist Generalist Specialist
Invasive Native
c c
ba
Tolerance score was calculated as the ratio of fitness (the total biomass) for damaged plants divided by the mean value of undamaged control in the same herbivore treatment in the common garden experiment.
Invasive plants better tolerate herbivory
(Journal of Ecology, 2010)
Summary• Invasive Triadica populations had lower resistance and higher
tolerance to the specialist caterpillar, compared to native populations.
• With respect to the response to the generalist caterpillar,invasive populations had greater tolerance as was the case for the specialist. No differences in resistance for introduced versus native populations.
• Plants from invasive populations have altered chemistry that has a larger impact on specialist resistance than on generalist resistance.
(3) Will insect population build-up be faster oninvasive plant populations than on those fromnative populations (lower resistance in theintroduced range) ?
(4) Under the same herbivore load will invasivepopulations perform better than nativepopulations (higher tolerance in the introducedrange) ?
Questions: biological control of Triadica
Predict potential biological control impactField common garden tests: leaf-rolling weevil
release weevils
(different density)
on caged plants
weevil numbers;
(question 3)
plant growth
(question 4)
Leaf-rolling weevil Heterapoderopsis bicallosicollis
Results: weevil populations
High Insect population on invasive plants than on natives
Generalist Specialist
cc c
ba
0
2
4
6
8
10
12
Num
ber o
f wee
vil
Invasive Native
0
2
4
6
8
10
12N
umbe
r of w
eevi
l
A one pair
B two pairs
Jul 29 Aug 26 Sep 23 Oct 21 Dec 03
0
2
4
6
8
10
12
Num
ber o
f wee
vil
Invasive Native
0
2
4
6
8
10
12N
umbe
r of w
eevi
l
A one pair
B two pairs
Jul 29 Aug 26 Sep 23 Oct 21 Dec 03
Invasive
Native
(Ecological Applications, preprint, 2010)
Results: plant growth
Invasive plants always grow better than natives,
regardless of insect number
(Ecological Applications, preprint, 2010)
Weevil number2 4 6 8
potential biological control impact
Field common gardentests:
larval numbers; 0, 4, 8per seedling
plant fitness
Caterpillar Gadirtha inexacta
potential biological control impact
Field common gardentests:
larval numbers; 0, 4, 8per seedling
plant fitness
Caterpillar Gadirtha inexacta
(Ecological Applications, preprint, 2010)
y = -0.337x + 18.663
y = -0.421x + 15.122
8
12
16
20
0 2 4 6 8 10
Tota
l bio
mas
s (g
)
Invasive/Light Native/Light
y = -0.346x + 86.872
y = -1.4x + 77.544
60
70
80
90
100
0 2 4 6 8 10
Larval number
Hei
ght (
cm)
(a)
(b)
y = -0.337x + 18.663
y = -0.421x + 15.122
8
12
16
20
0 2 4 6 8 10
Tota
l bio
mas
s (g
)
Invasive/Light Native/Light
y = -0.346x + 86.872
y = -1.4x + 77.544
60
70
80
90
100
0 2 4 6 8 10
Larval number
Hei
ght (
cm)
(a)
(b)
Invasive
Native
Invasive
Native
Summary• Weevils (potential biocontrol agent) achieved greater
population densities when they fed on invasive trees than on natives, due to lower resistance of the invasive populations.
• Invasive plants had greater herbivore tolerance such that the impact of both potential insect agents (weevil and moth) on plant performance was lower than on native populations (despite higher herbivore loads on those plants).
Discussions: novel interactions• Differences in selective pressures between ranges have
caused dramatic reductions in resistance to specialist herbivores and those changes in plant secondary chemistry likely underlie these differences.
• Increase in tolerance to herbivory appears to (at least partly) reflect an increase in growth rate in the introduced range.
• Greater tolerance to generalist herbivores suggests the possibility of selection for traits that allow plants to tolerate generalist herbivores more than specialist herbivores.
Implications for biological control• Reduced resistance and increased tolerance to herbivory in
introduced populations mayimpede success of biological control, although the insects can reach high density.
• To improve the prediction of insect impact, biological control practitioners should
include plants from the introduced range in the pre-release evaluation and examine novel interactions of insects and invasive populations.