Feeding preferences of the generalist herbivore, femurrubrum , 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 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 (: ) 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 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