Feeding preferences of the generalist insect herbivore, Melanoplus femurrubrum grasshopper, on invasive and native plants
Alina Avanesyan and Theresa Culley Department of Biological Sciences, University of Cincinnati
http://www.projectnoah.org The interaction between plants and insect herbivores
A herbivore attacks a plant Feeding behavior native
Generalist ? invasive insect
? native
The plant defenses respond ? invasive Plant responses to insect feeding Enemy Release Hypothesis (Darwin 1859, Williams 1954, Elton 1958, Gillett 1962)
Native range Introduced range
(modified from Keane & Crawley, 2002) Main question Do generalist herbivores prefer to feed on native plants rather than on invasive plants?
• Generalist grasshoppers feed on a wide variety of plants • They often switch between plants • They prefer new food Main hypothesis Melanoplus femurrubrum grasshoppers will be more active and feed more on invasive plant species. Study Organisms
Food range
http://thingsbiological.wordpress.com Wyoming Agricultural Experiment Station Bulletin 1994 Melanoplus femurrubrum (Orthoptera: Acrididae) Red‐legged Grasshopper Study Organisms (cont.)
Andropogon Bouteloua Miscanthus Miscanthus Gerardii Curtipendula sinensis sinensis Big Bluestem Sideoats Grama ‘Zebrinus’ 'Gracillimus’ Zebra Grass Maiden Grass
Native grasses Invasive grasses Family: Poaceae Feeding experiments
No‐choice Choice
Plants Leaves
Field Greenhouse Study Sites
Western Maryland Research and Education Center (MD) Experiments with nymphs
Cincinnati Center for Field Studies (OH) Experiments with adult grasshoppers
University of Cincinnati Greenhouse (OH) Experiments with adult grasshoppers Main hypothesis Melanoplus femurrubrum grasshoppers will be more active and feed more on invasive plant species. Research questions
1. Does leaf damage from grasshoppers differ in native and invasive plants? 2. Does feeding activity of grasshoppers differ on native and invasive plants?
3. Does food intake of grasshopper differ on native and invasive plants? 4. Does feeding rate of grasshopper differ on native and invasive plants? Measurements
“Scar”
Leaf damage: Volume of the grazed Food intake: Weight of food portion [length ×width ×depth of “scars”, consumed [food offered‐food not mm3] eaten, g] Feeding activity: Frequency of “scarring” Feeding rate: [food [number of scars/number of leaves] intake/grasshopper weight, g/g/d] Results: Greenhouse experiments
5 hours 5 days
Andropogon Miscanthus gerardii sinensis Big Bluestem ‘Zebrinus’ Zebra Grass
Native/invasive plant pair Feeding plants Leaf Volume of grazedDamage portion, mm3
0 20 40 60 80 100 120 damage
Andropogon than χ
²(1)=4.36, Native activity gerardii Results:
on Leaf
=2n=12 n=12 from am
native of
p
damage
grasshoppers grasshoppers <
0.05 Plant
Andropogon
Miscanthus Invasive Greenhouse sinensis
was did plants.
not
significantly differ
FrequencyProp of “scarring”
0 10203040506070 significantly χ
²(1)=3.32, greater Andropogon
experiments Native gerardii of Feeding = n=10 n=9
am grasshoppers
on
p between
> invasive
0.05 Plant
activity
Miscanthus Invasive plants.
sinensis Miscanthus
Food Log(FoodLog consumed)
-1.7 -1.6 -1.5 -1.4 -1.3 intake Andropogon Native gerardii Results: and of =2n=12 n=12 am Food
grasshoppers feeding
Plant intake F
1,20 aeof rate Miscanthus =0.007, Invasive sinensis
Greenhouse
grasshoppers
P>
0.05
did
Log(FeedingFeedRateLog rate)
not -1.3 -1.2 -1.1 -1.0 -0.9 -0.8 differ Andropogon Native gerardii
experiments
of significantly =2n=12 n=12 am Feeding
grasshoppers
Plant F between 1,20
Miscanthus rate Invasive =0.105, sinensis
plants. P> 0.05
Next: ‐ Two native/invasive plant pairs included in analysis ‐ Field experiment (more similar to natural conditions)
Andropogon Miscanthus sinensis gerardii ‘Zebrinus’ Native/invasive plant pairs 5 days
5 hours Bouteloua Miscanthus sinensis curtipendula 'Gracillimus’ Volume of DamageSqgrazed portion between Leaf 246810
damage Invasive plants plants. =2n=12 n=12 in Leaf
and Results:
damage feeding Type F 1,20 =2.52, Native plants
ciiyof activity
P>
0.05 Field
grasshoppers
FrequencyPropSq of “scarring” experiments 0.1 0.2 0.3 0.4 0.5
did Invasive plants of Feeding =2n=12 n=12
not
in grasshoppers
differ
Type
activity F
1,20 significantly Native plants =2.72,
P>
0.05
Food consumed,FoodMD g
0.015 0.020 0.025 0.030 0.035 0.040 0.045 Both Invasive plants Results: of
=4n=14 n=14 food
Food in grasshoppers
intake
Type intake F 1,24
Native plants and =13.08,
Experiments
feeding
P<
0.05 rate were FeedingFeedRate rate, g/g/d
0.04 0.06 0.08 0.10 0.12 greater
Invasive with plants of =4n=14 n=14
in on
Feeding grasshoppers invasive
Type
F leaves 1,24
=16.39, rate plants. Native plants
P<
0.05 Conclusions Main hypothesis: Melanoplus femurrubrum grasshoppers will be more active and feed more on invasive plant species. The hypothesis was supported in the experiments with leaves but was not supported in the experiment with intact plants.
• differences in grasshopper feeding under natural (intact plants) and artificial (leaves) conditions: needs to be further examined
• decreasing in resistance of plant leaves after they have been clipped
Main question: Do generalist herbivores prefer to feed on native plants rather than on invasive plants? No. Melanoplus femurrubrum grasshoppers did not show any feeding preferences towards native plants. Significance to the field of study
•Economic losses •Human health problems Control is costly Invasive • Changes in natural plants (Pimental et al., 2005) communities •Loss of biodiversity etc.
Feeding preferences of generalist insects regarding to invasive and native plants are still uncertain
Effective pest control The choice of Convenient plant‐insect strategies in order to grasshoppers: model (may be used preserve biodiversity agricultural importance and extended in native communities. (Hewitt & Onsager, 1983) in future studies) Thank you!
Advisor: Dr. Theresa Culley
Committee Members University of Cincinnati: Roger Ruff Dr. Joshua Gross Angelo Randaci Dr. William Lamp Dr. Stephen Matter Dr. George Uetz University of Maryland: Tim Ellis
Wieman Wendel Benedict Award 2011, 2012. University of Cincinnati Graduate Research Fellowship for Outstanding Incoming PhD Students, 2009. University of Cincinnati