indirect interactions between plants mediated by insect herbivores alejandro benhumea
TRANSCRIPT
Indirect interactions between plants mediated by insect herbivores
Alejandro Benhumea
Water
Water
+-
+
-Associational Susceptibility
Direct Interactions
Indirect Interactions
Overview
•Plants•Bugs•Hypothesis•Methods•Data•conclusion•Q&A
Opuntia imbricata (cholla) &
Opuntia phaeacantha (Prickly Pear)
Cholla Cacti•Grows in cylindrical segments.
•Main plant density occurs at the base of los pinos.
• Structure prevents plant from being eaten by larger mammals
•Cholla are much more abundant than the prickly pear
Prickly Pear Cacti
Fruits
Cladodes
•Juveniles/Adults
•Reproduction
•Predators
•Insect abundance
Narnia pallidicornis
Adult
Old Fruit
Juvenile
Proboscis
Reproduction Eggs
•Juveniles will depend on their host plant until they are adults.
•Juveniles that have hatched
Hypothesis 1
“Bug abundance on cholla cacti is greater on plants closer to the prickly pear cacti”.
Method•Chose random Prickly pear and surveyed the surrounding cholla within a 15 m Radius.
•Surveyed 108 Cholla plants
•Took GPS coordinates for each plant with an accuracy of ~.5-1 meter to be able to measure plant distances.
LegendCactus Sample Points
°0 100 20050
Meters
Data
5-100 0-5 m 10-15
0.5
1
1.5
2
2.5
3
3.5
4
Bu
gs p
er
cho
lla
no significant effect of distance
A
A
A
2006 Observational Data
Distance from prickly pear
2004 Observational Data.
0
1
2
3
4
5
6
7
8
9
10
0-5 m 5-10 m 10-15 m
bu
gs
per
pla
nt
significant effect of distance, P = 0.015A
B
B
Distance from prickly pear
04-06 comparison of prickly pear Fruit Production
0
10
20
30
40
50
60
70
80
# o
f fr
uit
s P
er
Pla
nt
2006 fruits
2004 fruits
L
Hypothesis 2
• “insects released on high quality plants will stay closer than insects released on low quality plants.
H
MethodsBug capture, marking and releasing. With a 24 hr wait time.
24 hr.
I will be marking and releasing 30 insects per plant.
Fruits
15
Or
5
Fruits were taken from nearby prickly pear and placed on the plant that would be in the experiment.
Prickly pear outside of experiment
Prickly pear inside the experiment
Predictions
•By simulating Over Population, the bugs will move out with proportion to the available food source.
•Bugs will feed on fruit even though it had been cut off from the plant.
•I am expecting the dispersal to be gradual over 2 or 3 days. Changed it to 24 hours
•I am also expecting this experiment to follow closely with
My first hypothesis.
Results of experimental release
0
0.02
0.04
0.06
0.08
0.1
0.12
0-5 5-10 10-15
pro
po
rtio
n r
eco
ver
ed p
er p
lan
t
low qualityhigh quality
no significant effects of treatment or distance
Distance from prickly pear
Predators
Jumping Spider Praying Mantis Northern Mockingbird
Conclusion.
• The associational interaction from insects varies from one time frame to another
• In a Arid ecosystem climate changes over the years influence fruit abundance and the indirect interaction of plants through a mediated insect herbivore.
Questions
??
??
?
?
?
??
?
?
?
?
?
?
A Big Thanks to…
• Sevilleta LTER
• Fish and Wildlife
• Jennifer Johnson
• Brenda Nieto
• Andrew Romenger
• Ashwana Fricker
• Tom Miller