Indirect interactions between plants mediated by insect herbivores

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Indirect interactions between plants mediated by
insect herbivores

• Alejandro Benhumea

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Direct Interactions
Water
Associational Susceptibility
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-


Indirect Interactions
Water
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Overview

• Plants
• Bugs
• Hypothesis
• Methods
• Data
• conclusion
• QA

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Opuntia imbricata (cholla) Opuntia phaeacantha
(Prickly Pear)
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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

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Prickly Pear Cacti
Cladodes
Fruits
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Narnia pallidicornis

• Juveniles/Adults
• Reproduction
• Predators
• Insect abundance

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Adult
Proboscis
Old Fruit
Juvenile
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Reproduction
Eggs

• Juveniles will depend on their host plant until
  they are adults.

• Juveniles that have hatched

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Hypothesis 1
Bug abundance on cholla cacti is greater on
plants closer to the prickly pear cacti.
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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.

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Data
2006 Observational Data
5-10
10-15
0-5 m
0
Distance from prickly pear
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2004 Observational Data.
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significant effect of distance,
P
0.015
A
9
8
7
6
B
5
bugs per plant
B
4
3
2
1
0
0-5 m
5-10 m
10-15 m
Distance from prickly pear
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04-06 comparison of prickly pear Fruit Production
80
70
60
50
2006 fruits
of fruits Per Plant
40
2004 fruits
30
20
10
0
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Hypothesis 2

• insects released on high quality plants will
  stay closer than insects released on low quality
  plants.

H
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Methods
Bug capture, marking and releasing. With a 24 hr
wait time.
24 hr.
I will be marking and releasing 30 insects per
plant.
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Fruits
Fruits were taken from nearby prickly pear and
placed on the plant that would be in the
experiment.
15 Or 5
Prickly pear inside the experiment
Prickly pear outside of experiment
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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.

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Results of experimental release
0.12
no significant effects of treatment or distance
0.1
0.08
proportion recovered per plant
low quality
0.06
high quality
0.04
0.02
0
0-5
5-10
10-15
Distance from prickly pear
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Predators
Jumping Spider
Praying Mantis
Northern Mockingbird
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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.

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Questions
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A Big Thanks to

• Sevilleta LTER
• Fish and Wildlife
• Jennifer Johnson
• Brenda Nieto
• Andrew Romenger
• Ashwana Fricker
• Tom Miller