The document describes research on the distribution of the invasive cactus moth (Cactoblastis cactorum) and its host plant (Opuntia stricta) in Florida. Researchers surveyed over 1,300 plots using stratified random and adaptive cluster sampling. They found the invasive moth primarily on O. stricta and O. humifusa var. ammophila. Generalized linear mixed models showed O. stricta occurrence was positively related to detritus density and vegetation density. Models also showed invasive moth occurrence on O. stricta was positively related to host plant height and percent cover. The research provides insights into factors that structure the occurrence of the invasive moth and its cactus host in Florida.

1. Predic'ng
the
Distribu'on
of
the
Invasive
Cactus
Moth,
Cactoblas)s
cactorum,
and
its
Major
Host
Plant,
Opun)a
stricta,
in
Florida
Kristen
E.
Sauby,
Mary
C.
Christman,
and
Robert
D.
Holt
Department
of
Biology
University
of
Florida
Ecological
Society
of
America
Annual
Mee'ng
Sacramento,
California
August
11,
2014

2. Florida
Opun)a
and
Their
Specialist
Insect
Herbivores
Invasive
Cactus
Moth,
Cactoblas)s
cactorum
Na've
Cactus
Moth,
Melitara
prodenialis
Na've
Cactus
Bug,
Chelinidea
vi7ger
Na've
Cactus
Scale,
Dactylopius
sp.
O.
stricta
O.
pusilla
O.
humifusa
var.
ammophila

3. The
invasive
cactus
moth,
Cactoblas)s
cactorum,
“blas'ng”
its
host
species,
Opun)a
stricta,
in
Florida

4. Background
• Opun%a
are
na&ve
to
the
New
World
(North
and
South
America)
• Including
the
phylogeny
and
“puta&ve
dispersal
pathways
of
Opun%a
clades”
(Majure
et
al.,
American
Journal
of
Botany,
2012)

5. The
Path
to
the
North
American
Introduc'on
First
introduced
into
Australia
to
control
invasive
cac&
1957
Early
1930s
1925
of
the
Invasive
Cactus
Moth
Approx.
na&ve
range
of
moth

6. Successful
Biological
Control
in
Australia
Before…
ARer.
“In
August
1930,
for
150
miles
[240
km]
along
the
river
the
pest
[O.
stricta]
was
in
its
full
vigour,
its
con&nuity
almost
unbroken
by
cleared
land;
the
pastoral
proper&es
had
been
overrun
and
mainly
deserted.”
• Quotes
from
Dodd
(1940)
• Photos
from
Osmond
et
al.
“…in
August
1932,
90
percent
of
the
[prickly]
pear
had
collapsed.
The
change
in
exactly
two
years
was
extraordinary.”
2008
(Journal
of
Experimental
Botany)

7. Distribu'on
of
the
Invasive
Cactus
Moth
in
the
Louisiana,
2009
Most
recent
detec&ons:
Jefferson,
Lafourche,
and
Terrebonne
Parishes,
Louisiana
(2009)
Southeastern
United
States
South
Carolina,
2004
First
detec'on,
Florida
Keys,
1989
Source:
USDA
APHIS,
h`p://www.aphis.usda.gov/plant_health/plant_pest_info/cactoblas&s/spread.shtml,
accessed
21
March
2009
NE
Florida,
2000

8. Ques'ons
• How
prevalent
is
the
invasive
cactus
moth
and
moth
damage?
• How
important
are
different
factors
in
structuring
varia&on
in
cactus
and
invasive
cactus
moth
occurrence?
– Abio&c
factors
(eleva&on)
– Bio&c
factors
(plant
density,
canopy
cover)
– Spa&al
factors

9. The
invasive
moth
is
found
primarily
on
O.
humifusa
var.
ammophila
and
O.
stricta
(Sauby
et
al.
2012)

10. Sampling
at
the
Guana
Tolomato
Matanzas
Na'onal
Estuarine
Research
Reserve
(GTMNERR)
• Plot
Surveys
• Plant
Surveys

11. • Set
Sampling
Scheme
–
Plot
Surveys
up
1-­‐meter2
plots
according
to
a
stra&fied
random
adap&ve
cluster
sampling
scheme
1. Stra&fied
Random
Sampling
(SRSWOR):
plots
randomly
distributed
across
(a)
5
islands
and
(b)
two
habitat
patches
(524
plots)
2. Adap&ve
Cluster
Sampling:
If
a
plot
had
cac&,
adjacent
plots
were
also
surveyed
(c)
(829
plots)
• Surveyed
plots
at
least
twice
a
year
(May
2012
–
present)
• Then
aggregated
data
for
analysis

12. • Set
Sampling
Scheme
–
Plot
Surveys
up
1-­‐meter2
plots
according
to
a
stra&fied
random
adap&ve
cluster
sampling
scheme
1. Stra&fied
Random
Sampling
(SRSWOR):
plots
randomly
distributed
across
(a)
5
islands
and
(b)
two
habitat
patches
(524
plots)
2. Adap&ve
Cluster
Sampling:
If
a
plot
had
cac&,
adjacent
plots
were
also
surveyed
(c)
(829
plots)
• Surveyed
plots
at
least
twice
a
year
(May
2012
–
present)
• Then
aggregated
data
for
analysis
(c)

13. • Set
Sampling
Scheme
–
Plot
Surveys
up
1-­‐meter2
plots
according
to
a
stra&fied
random
adap&ve
cluster
sampling
scheme
1. Stra&fied
Random
Sampling
(SRSWOR):
plots
randomly
distributed
across
(a)
5
islands
and
(b)
two
habitat
patches
(523
plots)
2. Adap&ve
Cluster
Sampling:
If
a
plot
had
cac&,
adjacent
plots
were
also
surveyed
(c)
(824
plots)
• Surveyed
plots
at
least
twice
a
year
(May
2012
–
present)
• Aggregated
data
for
analysis
(c)

14. Sampling
Scheme
–
Plant
Surveys
• Mapped
and
marked
individual
cactus
plants
in
a
random
subset
of
plots
(287
plots;
1089
O.
stricta
and
1087
O.
pusilla
plants)
• Surveyed
all
at
least
twice
a
year
(Jan.
2013
–
present)
• Aggregated
data
for
analysis

15. Prevalence
of
Cac'
in
SRSWOR
Plots
• Propor&on
of
area
occupied
by
each
cactus
species
• O.
humifusa
var.
ammophila
was
rare
(found
in
only
1
plot)
500
400
300
200
100
Absent Present
Number of plots
O. stricta
500
400
300
200
100
O. pusilla
Absent Present
75/523
=
14.3%
45/523
=
8.6%

16. Sample
Size
of
Plots
with
Cac'
aRer
Adap've
Cluster
Sampling
• Increased
the
number
of
plots
with
cac&
1100
1000
900
800
700
600
500
400
300
200
100
Absent Present
Number of plots
O. stricta
1100
1000
900
800
700
600
500
400
300
200
100
O. pusilla
Absent Present
447/1347
=
33.2%
324/1347
=
24.1%

17. 400
350
300
250
200
150
100
50
Prevalence
of
the
Invasive
Cactus
Moth
Aggregated
Plot
Survey
Data
(May
2012
–
present)
Moth
Absent
Moth
Present
Number of plots
O. stricta
400
350
300
250
200
150
100
50
O. pusilla
Moth
Absent
Moth
Present
54/447
=
12.1%
1/324
=
0.31%
Presence
=
moth
larvae
and/or
eggs
were
found
at
least
once
Absence
=
moth
larvae
and/or
eggs
never
observed

18. 400
350
300
250
200
150
100
50
Prevalence
of
the
Invasive
Cactus
Moth
Moth
Absent
Moth
Present
Number of plots
O. stricta
400
350
300
250
200
150
100
50
O. pusilla
Moth
Absent
Moth
Present
1100
1000
900
800
700
600
500
400
300
200
100
Moth
Absent
Moth
Present
Number of plants
O. stricta
35/1089
=
3.2%
Aggregated
Plot
Survey
Data
(May
2012
–
present)
Aggregated
Plant
Survey
Data
(January
2013
–
present)
54/447
=
12.1%
1/324
=
0.31%
Presence
=
moth
larvae
and/or
eggs
were
found
at
least
once
Absence
=
moth
larvae
and/or
eggs
never
observed

19. Prevalence
of
Damage
from
Past
Moth
Infesta'ons
O. pusilla
54/449
=
12%
350
300
250
200
150
100
50
Damage
Absent
Damage
Present
Number of plots
O. stricta
350
300
250
200
150
100
50
Damage
Absent
122/324
=
38%
Damage
Present
334/447
=
75%
• An
es&mate
of
cumula&ve
prevalence
of
cactus
moths
• Many
plants
are
infested
at
some
point
in
their
lives
• Es&mates
may
be
biased
low
because
only
live
plants
are
surveyed
• Caveat:
damage
may
be
from
either
the
invasive
and/or
na&ve
cactus
moths

20. Hypothesized
Dynamics
of
Cactus
Moth
Invasion
N
cac&
t
invasive
cactus
moth
Current
state
of
invasion

21. Generalized
Linear
Mixed
Models
to
Explain
Paherns
of
O.
stricta
Occurrence
Analyzed
in
SAS
v.
9.4
using
GLIMMIX
procedure
Dependent
Variables
• O.
stricta
presence
Fixed
Effects
• Eleva&on
(meters)
• Vegeta&on
Class
(five
categories)
• Vegeta&on
Density
(scale
of
0
–
4)
• Detritus
Density
(scale
of
0
–
4)
• Canopy
(yes/no)
Random
Effects
• Habitat
Patch
• Network
(the
adap&ve
cluster
to
which
a
plot
belongs)

22. Results
-­‐
Generalized
Linear
Mixed
Models
to
Explain
Paherns
of
Cactus
Occurrence
Tests
of
Fixed
Effects
Effect Es'mate St.
Error Pr
>
F
Canopy 0.17 0.33 0.5970
Vegeta&on
Class -­‐ -­‐ 0.0007
Vegeta&on
Density 0.38 0.12 0.0010
Detritus
Density 0.42 0.11 <.0001
Eleva&on
(m) 0.037 0.10 0.7153

23. Results
–
Rela'onship
Between
Vegeta'on
Class
and
O.
stricta
Occurrence
Least
Squares
Means
Vegeta'on
Class
Mean
Prob(Y=1)
Standard
Error
t
Value
Pr
>
|t|
Marsh
plants
0.0097
0.0081
-­‐5.50
<.0001
Mixed
forbs
0.16
0.059
-­‐3.78
0.0002
Overhanging
cedar/mixed
forbs
0.14
0.057
-­‐3.83
0.0001
Palm/palme`o
0.00014
0.0022
-­‐0.57
0.57
Shrubs/vines
0.083
0.039
-­‐4.64
<.0001

24. Generalized
Linear
Mixed
Model
to
Explain
Paherns
of
Invasive
Cactus
Moth
Occurrence
on
O.
stricta
• Limited
analysis
to
plots
containing
O.
stricta
• Analyzed
in
SAS
v.
9.4
using
GLIMMIX
procedure
Dependent
Variable
• Invasive
Cactus
Moth
presence
Fixed
Effects
• O.
stricta
maximum
height
• O.
stricta
percent
cover
• Eleva&on
(meters)
• Vegeta&on
Class
(seven
categories)
• Vegeta&on
Density
(scale
of
0
–
4)
• Detritus
Density
(scale
of
0
–
4)
• Canopy
(yes/no)
Random
Effects
• Network
(the
adap&ve
cluster
to
which
a
plot
belongs)
• Did
NOT
include
Habitat
Patch
because
it
was
not
sta&s&cally
significant
in
a
model
with
only
random
effects

25. Results
-­‐
Generalized
Linear
Mixed
Model
to
Explain
Paherns
of
Invasive
Cactus
Moth
Occurrence
on
O.
stricta
Effect
Es'mate
St.
Error
Pr
>
F
Canopy
0.21
0.7751
0.79
Vegeta'on
Class
-­‐
-­‐
0.52
O.
stricta
Height
0.042
0.016
0.011
O.
stricta
Percent
Cover
0.038
0.018
0.037
Eleva'on
0.23
0.094
0.013
Detritus
0.046
0.22
0.84

26. Conclusions
• Abio&c
and
bio&c
factors
can
be
used
to
explain
pa`erns
of
cactus
and
cactus
moth
occurrence
O.
stricta
occurrence
• Posi&ve
rela&onship
with
detritus
and
vegeta&on
density
• Significant
varia&on
among
vegeta&on
classes

27. Conclusions
Invasive
cactus
moth
occurrence
• Cumula&ve
damage
is
much
greater
than
present
rates
of
infesta&on
• Rare
on
O.
pusilla
• Posi&vely
related
to
O.
stricta
height
and
percent
cover
as
well
as
eleva&on
Spa&al
factors
• Habitat
patch
and
Network
included
in
models
of
cactus
occurrence
as
random
effects

28. Invasive
Species
Management
• Important
to
consider
the
rela&ve
threat
of
the
species
• Important
to
account
for
spa&al
varia&on
in
risk
of
invasion
and
costs
of
surveillance
(Epanchin-­‐Niell
et
al.,
Ecol.
Le;.,
2012)

29. Future
Work
• Assess
temporal
and
spa&al
autocorrela&on
in:
– the
dynamics
of
cactus
and
cactus
moth
occupancy
• Assess
threat
of
the
invasive
cactus
moth
to
cac&
using
demographic
models

30. Acknowledgments
University
of
Florida
• Michael
Barfield
• James
Nifong
• Doria
Gordon
• Robert
Fletcher
• Jose
Miguel
Poncianco
• Jake
Ferguson
• Rosana
Zenil-­‐Ferguson
• Polly
Harding
(pictured)
Feel
free
to
contact
me
at
ksauby@ufl.edu
GTMNERR
• Ka'e
Petrinec
• Mah
Welsh