Are Plants Enough: The Relative Importance of Plants and Nutrients to Insect Communities

Chelse Prather, PhD

•  Grew up in Northern Kentucky •  BS, biology, University of Kentucky •  PhD, biology, University of Notre Dame, research

in the rainforest in Puerto Rico •  Previous Postdoc, biology/history/philosophy,

Florida State University •  Now Research Faculty at University of Houston

Prairie restoration and management

•  Focus on restoring and managing for diverse native plant communities or creating habitat for game, migratory and threatened species.

•  What about the smaller animals—the invertebrates?

•  Butterflies, the “pretty” invertebrates have been mentioned.

•  What about all the others?

Outline 1.  Why care about invertebrates?

Invertebrates and humans 2.  Research question: What

determines invertebrate herbivore community structure in coastal tallgrass prairies?

3.  Other projects 4.  How to use this information?





Invertebrates: •  Represent over 80% of all known

eukaryotic species •  Fill a vast array of ecological

niches • Attain high biomass in most

ecosystems.

Do insects affect humans?

Ecosystem services: Benefits from ecosystems that support human life and well-

being

Some%invertebrates%cause%problema2c%disservices%

The little things that run the world

E. O. Wilson

“…If invertebrates were to disappear, I doubt that the human species would last more than a few months.”%

Invertebrates, ecosystem

services, climate change

Chelse M. Prather, Shannon Pelini, Angela Laws, Emily Rivest, Megan Woltz, Christopher P. Bloch, Izzy Del

Torro, Chuan-Kai Ho, John Kominoski, T. A. Scott Newbold, Sheena Parsons.

2012. Biological Reviews, in press.

Goal: Evaluate invertebrate influences on ecosystem services and how these

influences may be altered by climate change

-On the National Bison range, it’s estimated that grasshoppers eat more vegetation than all the large vertebrates combined (Belovsky 2002).

Invertebrate effects on ecosystem services

- Can eat 0-100% of plant biomass in

an ecosystem

- 11,000 species of

myrmechores

-3/4 of all plants and 1/3 of all crops

by volume are pollinator-

dependent

%

!Dung&beetles&that&decompose&feces&are&worth&es6mated&at&$454&million&in&the&US&

%

!Emerging&insect&cause&huge&changes&in&available&nutrients%

!Invertebrate&frass&can&increase&or&decrease&nutrients&to&plants%

%

%

%

%

%

%

%

Invertebrate effects on ecosystem services%

Food web stability

%

In summary:

•  Invertebrates provide or indirectly influence all ecosystem services.

•  They are the major providers of a few services, and influence most of the others to a great degree.

•  BUT: the basic science has not been done to evaluate their relative importance.





Fundamental question in ecology:

What is the relative importance of factors that affect the abundance and

diversity of organisms?

Why grasshoppers?

•  One of the major herbivores in most prairies across the US

•  Can eat more than ungulate herbivores combined

•  Relatively easy to sample

Herbivore abundance

Herbivore community characteristics

Herbivore diversity

Plant community characteristics

Plant biomass Plant diversity Plant micro-

nutrients Plant macro-

nutrients

P L A N T Q U A L I T Y

Precipitation &

temperature

Site characteristics

C L I M A T E

Soil macro-nutrients

Soil micro-

nutrients

G E O L O G Y

Land use & management

Fragment size

Time since restoration

H U M A N I N F L U E N C E S

Top down controls

Predator pressure &

Parasite load

X

X

Herbivore abundance


Herbivore diversity




nutrients

P L A N T Q U A L I T Y

Precipitation &

temperature


C L I M A T E


Soil micro-

nutrients

G E O L O G Y


Fragment size



Top down controls

Predator pressure &

Parasite load

X

X

Pristine prairie Restored prairie

Shell-rich area Invasive forest

Measured grasshopper diversity and density, and possible predictors across 3 habitats (n=12).

Predators  Wolf spider density

Soil  Moisture

 Oyster shell content  pH

Plant community  Biomass  Diversity  Water

 Plant height  Macro-nutrients

(N, P)  Micro-nutrients (Ca, Cu, Fe, K, Mg,

Mn, Na, S, Zn)  Root biomass  Root moisture

0%

2%

1% 2%

Herbivores%(orthopterans)%

df%=%22%t%=%=2.54%

P%=%<%0.019%%%

0%

5%

1% 2%

Detri2vores%(isopods)%df%=%22%t%=%=2.00%

P%=%<%0.058%%%

0%

1%

2% Omnivores%(crayfish)%

df%=%22%t%=%5.79%

P%=%<%0.001%%%

0%

0.08%

0.16%

1% 2%

Predators%(wolf%spiders)%df%=%22%t%=%=6.92%P%=%%0.496%%%

Nu

mb

er o

f in

div

idu

als

pe

r m2

Shell-rich areas Pristine prairie Density of food web members

Significant drought event in 2011 Herbivore

abundance


Herbivore diversity




nutrients

Precipitation &

temperature


C L I M A T E


Soil micro-

nutrients

G E O L O G Y


Fragment size



Top down controls

Predator pressure &

Parasite load

X

X

Results

Precipitation &

temperature

Soil moisture

Single-factor, bivariate

relationships; build up to multiple

factors.

Herbivore abundance


Herbivore diversity




nutrients

Precipitation &

temperature


C L I M A T E


Soil micro-

nutrients

G E O L O G Y


Fragment size



Top down controls

Predator pressure &

Parasite load

X

X

Predator pressure &

Parasite load

Results

Herbivore abundance


Herbivore diversity


Plant diversity Plant biomass Plant micro-


nutrients

Precipitation &

temperature


C L I M A T E


Soil micro-

nutrients

G E O L O G Y


Fragment size



Top down controls

X

X

Predator pressure &

Parasite load

Plant biomass

Results

Results

Herbivore abundance


Herbivore diversity


Plant biomass Plant diversity

Plant micro-nutrients

Plant macro-nutrients

Precipitation &

temperature


C L I M A T E


Soil micro-

nutrients

G E O L O G Y


Fragment size



Top down controls

X

X

Predator pressure &

Parasite load

Plant diversity

Nitrogen

Results Phosphorus

Herbivore abundance


Herbivore diversity


Plant biomass

Plant diversity



Precipitation &

temperature


C L I M A T E


Soil micro-

nutrients

G E O L O G Y


Fragment size



Top down controls

X

X

Predator pressure &

Parasite load

Plant macro-nurients

Results Calcium Potassium

Herbivore abundance


Herbivore diversity




Precipitation &

temperature


C L I M A T E


Soil micro-

nutrients

G E O L O G Y


Fragment size



Top down controls

X

Plant biomass

Plant diversity

Predator pressure &

Parasite load

Sodium Sulfur

Plant micronutrients X

Results

Herbivore abundance


Herbivore diversity




Precipitation &

temperature


C L I M A T E


Soil micro-

nutrients

G E O L O G Y


Fragment size



Top down controls

X

Plant biomass

Plant diversity

Predator pressure &

Parasite load

Results

Herbivore abundance


Herbivore diversity




Precipitation &

temperature

C L I M A T E


Soil micro-

nutrients

G E O L O G Y


Fragment size



Top down controls

Plant biomass

Plant diversity

Predator pressure &

Parasite load

Results

Herbivore abundance


Herbivore diversity




Precipitation &

temperature

C L I M A T E


Soil micro-

nutrients

G E O L O G Y

Land use & manage-

ment Fragment

size Time since restoration


Top down controls

Plant biomass

Plant diversity

Predator pressure &

Parasite load

Results

Herbivore abundance


Herbivore diversity




Precipitation &

temperature

C L I M A T E


Soil micro-

nutrients

G E O L O G Y

Land use & manage-

ment Fragment



Top down controls

Plant biomass

Plant diversity

Predator pressure &

Parasite load

Dependent variable

Predictors (coefficent)

R2 P F

Density P (0.456) Soil moisture (-0.866)

Fe (-0.564) N (-0.649)

Veg height (-0.219) Plant diversity (0.501)

Ca (0.478)

0.48 <0.001 11.59

Richness K(0.920) S (-0.687)

0.35 <0.001 7.653

Dependent variable

Predictors (coefficent)

R2 P F

Grass-feeder density

N:P 0.221 0.006 5.105

Mixed-feeder density

Ca (0.014) Roots (-0.229)

Zn (0.734)

0.732 <0.001 30.755

Forb-feeder density

Ca (1.453) P (-0.561) Na (0.475) Zn (-0.322)

0.791 <0.001 4.763

CONCLUSION: What is the relative importance of factors that affect the abundance

and distribution of prairie herbivores?

Herbivore abundance


Herbivore diversity




Precipitation &

temperature

C L I M A T E


Soil micro-

nutrients

G E O L O G Y

Land use & manage-

ment Fragment



Top down controls

Plant biomass

Plant diversity

Predator pressure &

Parasite load

Conclusions: If you build it, will they come?

Katydid: Orchelimum

vulgaris

Grasshopper: Melanoplus

femurrubrum

Grasshopper: Metataplea brevicornis

Katydid: Concephalus

strictus

Species%specific%effects%

=100%

=50%

0%

50%

100%

=100%

=50%

0%

50%

100%

Grass%feeders% Mixed%feeders%

2%Grass% 2%Mixed%Both%

Grasshopper%diversity%conclusions%

•  The%number%of%species%doesn’t%necessarily%maSer,%but%the%iden2ty%of%the%species%you%have%maSers.%

•  Next—bigger%experiment%at%more%sites.%

**Disclaimer: understanding of what controls communities, not to be used to manage insects with current results**

Documents

Are Plants Enough: The Relative Importance of Plants and Nutrients to Insect Communities