The dogbane beetle - Latornell Conservation Symposium

The dogbane beetle: A native beetle’s
resilience in the face of invasive dog
strangling vine.
Rhoda deJonge, Faculty of Forestry - University of Toronto
Sandy Smith, Faculty of Forestry - University of Toronto
Robert Bourchier, Agriculture and Agri-Food Canada
Dog Strangling Vine (DSV)
Vincetoxicum rossicum (Kleopow) Barbar. (Apocynaceae)
Dog Strangling Vine (DSV)
Source: Ukraine, early 1900’s.
Success Factors:
 No damaging herbivores in North America1,2
Credit: Richard Dickinson
 Chemical antofine – limits native plant3
growth
 High seed production4 and root-shoot ratio5
Control
Methods:
Control
Methods:
 resistant to chemical and mechanical controls6,7,8
 biological control (using an insect to control this weed)
Native herbivores & introduced plants

Native herbivores utilizing introduced17
Colorado potato beetle feeds on bittersweet nightshade
plants
 Soapberry bugs feed on Asian goldenrain tree
18
 Weevils feed on Eurasian water-milfoil and controlling
spread 19
 Tephritid fruit fly speciating and feeds on east Asian
honeysuckles 20
 Mustard white adapting to garlic mustard
21
The Dogbane Beetle
Chrysochus auratus Fabricius (Coleopetera: Chrysomelidae)
Ecological host-range:
 Specialist on dogbane plants
(Apocynum cannabinum and
A. androsaemifolium) throughout
eastern North America
Credit: Johan de Zoete
Uni-voltine Life cycle:
 Adults feed on plant leaves
 Females oviposit (lay eggs) on plants and stems
 Larvae feed on plant roots
 Over-winters as pupae in the soil
Dogbane Beetle – Victor over DSV?
Potential herbivore of DSV?:
 Same genus as the European Eumolpus beetle
(Chrysochus asclepiadeus), a specialist on plants in the
DSV’s genus. and the most damaging classical bio-control
candidate.15,16
 Similar life-cycle as the Eumolpus beetle.
 Dogbane and DSV are in the same
plant family (Apocynaceae)
 The plant and the beetle co-exist in
the field
Eumolpus beetle
Chrysochus asclepiadeus
Dogbane beetle – Victim of DSV?
Causes for concern:
 Dense stands can form monocultures
and harm forest understories and tree
plantations2,9,10
 Threatens rare plant species9,10,14
 Thick stands of dog strangling vine
support a lower number of arthropods.1
 Can act as an oviposition sink for
monarch butterflies11,12,13
Credit: Peter J. Bryant, UC Irvine
Objectives
Determine current/potential relationship between our native
dogbane beetle and DSV by testing:
1. Adult beetle’s feeding ability
2. Adult female beetle’s oviposition preferences
3. Larvae root-feeding and development
Tested members of dogbane, milkweed and DSV genera.
All in the (same) family
Apocynaceae
Apocynoideae
Asclepioideae
Dog-strangling vine
Vincetoxicum spp.
Milkweed
Asclepias spp.
Dogbane
Apocynum spp.
Objective 1: Adult feeding
Prediction:
Adult dogbane beetles will not feed or nibble
on plants other than their hosts (dogbane).
Methods:
No choice test: single beetles (n=74)
placed in petri dishes with moist filter paper
and one leaf of test plant. Leaves scanned
before and after test to determine feeding.
Looked at feeding and # of nibbles.
Results: Adult feeding
a
Ranked mean ‘nibbles’
were not statistically
different for milkweeds
and DSV –but were
different from other
common weeds.
2
3
4
0
b
1
b
c
0
bites$Bitenumber
# of bites per leaf
tes
400
500
Adults fed significantly
more on dogbane leaves
than on non-hosts.
dogbane
milkweed
dog strangling vine
goldenrod
(n=74)
(n=74)
(n=73)
(n=75)
Kruskal Wallis
=16.23, 2, p<0.0001
Victor or Victim?
0.5
0.5
DSV
Dogbane beetle
Objective 2: Adult female oviposition
Prediction:
Adult dogbane beetles will not oviposit (lay
eggs) on plants other than their hosts.
Methods:
Two adults (m/f) placed on potted plant pairs:
dogbane & dogbane (n=20)
dogbane & DSV (n=20)
dogbane & milkweed (n=20)
Egg mass # and location recorded throughout
test. After 17 days, adults were removed.
Credit: Johan de Zoete
Results: Oviposition
25
b
15
20
All three species paired with
the beetle’s host, dogbane.
The lowest percentage of egg
masses were laid on DSV.
10
c
5
% of masses on plant
30
35
a
n=20
n=20
dogbane
milkweed
n=18
dog strangling vine
(Kruskal Wallis =24.052, 2, p<0.0001)
Victor or Victim?
0.5
1.0
0.5
DSV
Dogbane beetle
Objective 3: Larval development
Prediction:
Larval dogbane beetles will not feed or
develop on plants other than their hosts.
Methods:
Larvae (n=20) placed at base of living plant
(n=10 for each test species). After 85 days,
pots were dissected and larvae were
counted and measured.
Results: Larval Development
No larvae were found on
DSV roots.
There was no significant
difference in number of
larvae surviving on
dogbane (66) and
milkweed (46) species.
Wilcox signed rank test p>0.05
Victor or Victim?
0.5
1.5
1.0
DSV
Dogbane beetle
Results: Larval Development/
Emergence
Number of larvae emerging from egg masses laid on different
plant species (dogbane, milkweed, DSV) was compared.
Kruskal Wallis: ranked mean # larvae emerging from egg
masses laid on different species is not significant.
(X2 = 2.1729, 2, p=0.3374).
Victor or Victim?
1.5
2.0
1.0
DSV
Dogbane beetle
Overall host-use of dogbane beetles
Apocynum androsaemifolium
Apocynum cannabinum
Asclepias syriaca
Asclepias speciosa
Asclepias incarnata
Asclepias eriocarpa
Asclepias fascicularis
Asclepias tuberosa
Asclepias currassavica
Vincetoxicum rossicum
Vincetoxicum nigrum
+++
+
-/+
adult
+++
+++
‐/+
+
+
+++
‐/+
‐
larvae
+++
+++
+
‐
‐
‐
+++
oviposition
+++
+++
+++
+++
+++
hosts
milkweeds
‐/+
+++
+++
Herbivory observed
Nibbling observed
No nibbling or herbivory observed
Nibbling observed in some populations, but not others
DSV
Conclusions: A moderately resilient beetle
 Adults will nibble on DSV, but do not
(yet?) have the capacity to feed.
 Female beetles will lay egg masses on
DSV and other vegetation.
 Dogbane beetle eggs able to develop to
1st instar on DSV just as easily as on
other plants.
 Larvae will feed and develop on roots of
plants more closely-related to DSV.
Victor or Victim?
1.5
2.0
DSV
Dogbane beetle
If DSV doesn’t out-compete dogbane in beetle habitats, the
beetle may not be directly harmed by the invasive vine’s
presence.
But the story doesn’t end there…
Credit: Johan de Zoete
Credit: www.e-celebrities.org/
Dog Strangling Vine out west?
 Cobalt beetle (Chrysochus cobaltinus) – broader host-
range than eastern sister species feeds on both: dogbane
and milkweeds.
 Host-range testing in process
Cobalt beetle adult feeding tests
300
250
200
150
a
Leaf size itself did not make
a difference in mm2 fed.
50
100
a
0
Reduction inhat$difference
surface area (mm2)
350
b
c
n=22
milkweed
n=22
dogbane
n=22
DSV
Only leaf species appears to
be significant in this test.
n=22
poppy
Kruskal Wallis
=51.81, 3, p<0.0001
Discussion
 Studying native species related to European enemies of
invasive plants may aid in identifying native insects that
can assist in biologically controlling invasive plants.
 How do we judge habitat impacts of potential native
biological control agents?
 Are there other ways we can better harness the services
of native species in order to reduce the spread of
invasive species?
Thank you!
Committee Members:
Sandy Smith, Advisor, University of Toronto
Robert Bourchier, Agriculture & Agri-Food Canada
Marc Cadotte, University of Toronto
Peter Kotanen, University of Toronto
Financial Assistance:
Ontario Graduate Scholarship
Invasive Species Centre
Faculty of Forestry
Agriculture and Agri-Food Canada
All Photo Credits: Rhoda deJonge – unless otherwise specified
Elbow Grease and Advice:
Richard Dickinson
Frank Oukhouia
Johan de Zoete
Janis Dickinson
Merrill Peterson
Royal Botanical Gardens
Works Cited
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2005
11. Cassagrande & Dacey, Environmental
2.
Milbrath, Environmental Entomology, 2010
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3.
Gibson et. al. Journal of Chemical Ecology,
2011
1.
Entomology, 2007
Experimentalis et Applicata 2003
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Ecology, 1998
4.
Cappuccino, Oikos, 2004
5.
Smith et.al, Canadian Journal of Botany,
2006
14. Bonanno, The Nature Conservancy – 1999
Douglass et. al., Invasive Plant Science
and Management, 2011
16. Weed et. al., Journal of Applied
Averill et. al., Invasive Plant Science and
Management, 2008
17. Hare, Annual Review of Entomology, 1990
8.
Lawlor & Raynal, Weed Science, 2002
19. Sheldon & Creed, Ecological Applications,
9.
Lawlor, State University of NY – thesis,
2000
6.
7.
10. DiTommaso et al., Canadian Journal of
Plant Science, 2005
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18. Carroll, Genetica, 2007
1995
20. Schwarz et al., Nature, 2005
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