Predictors of Insect Diversity and Abundance in a Fragmented Tallgrass Prairie Ecosystem

254 Pages·2017·1.78 MB·English

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Dissertations & Theses in Natural Resources Natural Resources, School of
4-2012
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Kody M. Unstad
University of Nebraska-Lincoln, [email protected]
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PREDICTORS OF INSECT DIVERSITY AND ABUNDANCE
IN A FRAGMENTED TALLGRASS PRAIRIE ECOSYSTEM

by
Kody Micah Shane Unstad

A THESIS

Presented to the Faculty of
The Graduate College at the University of Nebraska
In Partial Fulfillment of Requirements
For the Degree of Master of Science

Major: Natural Resource Sciences

Under the Supervision of Professor Craig R. Allen

Lincoln, Nebraska
April, 2012
PREDICTORS OF INSECT DIVERSITY AND ABUNDANCE
IN A FRAGMENTED TALLGRASS PRAIRIE ECOSYSTEM
Kody Unstad, M.S.
University of Nebraska, 2012
Advisor: Craig Allen
Despite providing many services, the tallgrass prairie and its ecological
community is one of the most endangered ecosystems in North America. Remaining
habitat exists as remnants in a highly-fragmented landscape. To make informed
conservation decisions we need to better understand the effects of this fragmentation.
Using the ecologically important insect groups, ants and ground beetles, this study
provides baseline data on the biological diversity of southeast Nebraska prairies and
investigates what management, landscape, and habitat characteristics affect them. Pitfall
trap sampling was conducted in 23 tallgrass remnants scattered throughout the Southeast
Prairies Biologically Unique Landscape in 2010 and 2011. Multi-model inference was
used for analysis of the data.
Twenty-eight species of ants were collected with the majority being grassland-
obligates. With a positive correlation, model selection results indicate that Shannon
diversity of grassland ants is best predicted by the average number of grass species per
m2 while their abundance is positively associated with the amount of nearby haymeadow.
Most ants belonged to the Opportunist and Cold Climate Specialist functional
groups. A comparison with prior studies indicates this functional group composition to be
most similar to cool-temperate forests. Though different habitats, their cooler climates
likely produce this similar composition.
Nineteen species of ground beetles were collected, with two species comprising
nearly 95% of the collection. These two species are incapable of flight, a physiological
factor that may contribute to their high abundances by leaving them hidden from
predators. As with grassland ants, the strongest predictor of Shannon diversity for ground
beetles was the average number of grass species per m2.
Results suggest that ants and ground beetles are non-randomly distributed in
relation to landscape, habitat, and management factors. High abundances of grassland-
obligate ants are associated with high amounts of haymeadow suggesting these areas may
be a priority for ant conservation. Results also suggest that sites with more grass species
sustain more diverse communities of ants and ground beetles, information that can be
incorporated into relevant conservation decisions.
iv

DEDICATION
To my parents, for letting me play outdoors.
To my wife, for letting me continue what my parents started.
v

ACKNOWLEDGEMENTS
I would first like to thank my advisor, Craig Allen, for providing me with
guidance, freedom, and humor, all of which have made this an enjoyable experience. I
would next like to thank Chris Helzer, for inspiring my interest in the prairie and for
always thinking outside the box. I would like to thank my graduate committee members,
LaReesa Wolfenbarger and Lance Meinke, as well as the many members of the Southeast
Nebraska Flagship Initiative. Your wisdom and experience is greatly appreciated.
Thank you to Jim Kalisch, for patiently teaching ant identification, and to Ashley
Pella, for spending countless hours in front of a microscope (even with a newborn baby).
I would like to thank Jim Schalles whose commitment to working long hours on
extremely hot days in July made collection of this data possible. I appreciate the support
of all my fellow graduate students in the Cooperative Unit, and Chris Wood at UNO. It is
nice to have others who can sympathize with your graduate school challenges.
Thank you to Stephen Winter, for being an excellent roommate for three summers
and sharing your ecological knowledge, charcoal grill, and fine beers. I also thank the
Salem United Church of Christ in Steinauer, NE for providing us with housing and being
great landlords and great people. I am especially indebted to the landowners of southeast
Nebraska for allowing me access to their haymeadows. I hope my study contributes to the
conservation of this beautiful and unique landscape.
I am thankful for the funding provided by the Nebraska Game and Parks
Commission and the United States Geological Survey that made this research possible.
The Nature Conservancy also provided partial support for this work through the Nebraska
Chapter’s J.E. Weaver Competitive Grants Program.
vi

Lastly, I would like to thank my family, especially my parents, for their love and
support of all my various endeavors over the years. Climbing trees, building forts,
running barefoot through cornfields, making backyard parody nature documentaries…the
childhood you gave me has made me who I am today. And most importantly, I would like
to thank my wonderful wife, Amanda, for her love and prayers, for allowing me to be
away the better part of two summers, for not freaking out when bags of insects appeared
in the freezer, and for standing by me through all of life’s challenges.
vii

TABLE OF CONTENTS
ABSTRACT………........................................................................................................... ii
DEDICATION.................................................................................................................. iv
ACKNOWLEDGEMENTS................................................................................................ v
TABLE OF CONTENTS................................................................................................. vii
LIST OF TABLES........................................................................................................... xii
LIST OF FIGURES......................................................................................................... xx
Chapter 1: INTRODUCTION………................................................................................ 1
THE TALLGRASS PRAIRIE……................................................................................. 1
Historical Background……................................................................................... 1
The Southeast Prairies Biologically Unique Landscape....................................... 3
Arthropod Communities…..................................................................................... 5
ANTS (HYMENOPTERA: FORMICIDAE)……......................................................... 6
Taxonomy…........................................................................................................... 6
Morphology…........................................................................................................ 7
Life Cycle…........................................................................................................... 8
Colony Life Cycle ….............................................................................................. 9
Eusociality …....................................................................................................... 10
Functional Groups…........................................................................................... 12
Ecology and Ecosystem Services…..................................................................... 13
GROUND BEETLES (COLEOPTERA: CARABIDAE)…........................................ 14
Taxonomy…......................................................................................................... 14
Morphology…...................................................................................................... 15
Life Cycle….......................................................................................................... 16
Ecology and Ecosystem Services…..................................................................... 17
THESIS OVERVIEW…............................................................................................... 19
LITERATURE CITED….............................................................................................. 21
viii

Chapter 2: DIVERSITY AND ABUNDANCE OF GRASSLAND, WOODLAND, AND
HABITAT-GENERALIST ANTS (HYMENOPTERA: FORMICIDAE) IN
REMNANT TALLGRASS PRAIRIE HAYMEADOWS…......................... 29
Abstract…............................................................................................................ 29
INTRODUCTION…..................................................................................................... 31
METHODS AND MATERIALS….............................................................................. 32
STUDY SITES…....................................................................................................... 32
STUDY DESIGN…................................................................................................... 34
Pitfall Trap Sampling…....................................................................................... 34
Sample Processing…........................................................................................... 35
Habitat Characteristics….................................................................................... 36
Landscape Characteristics…............................................................................... 38
Management…..................................................................................................... 39
STATISTICAL ANALYSES…................................................................................. 41
Habitat Preference…........................................................................................... 41
Diversity, Abundance, and Species Richness…................................................... 41
Multi-model Inference…...................................................................................... 42
RESULTS….................................................................................................................. 43
Grassland-obligate Ants…................................................................................... 44
Habitat-generalist Ants….................................................................................... 45
Woodland-obligate Ants…................................................................................... 46
DISCUSSION…............................................................................................................ 46
Grassland-obligate Ants…................................................................................... 48
Habitat-generalist Ants…..................................................................................... 49
Woodland-obligate Ants…................................................................................... 50
Conclusion…........................................................................................................ 50
LITERATURE CITED….............................................................................................. 52
TABLES AND FIGURES…......................................................................................... 56
ix

Chapter 3: FUNCTIONAL GROUP COMPOSITION OF ANTS (HYMENOPTERA:
FORMICIDAE) IN A GRASSLAND ECOSYSTEM…............................... 75

Abstract…............................................................................................................. 75
INTRODUCTION…..................................................................................................... 77
METHODS AND MATERIALS….............................................................................. 79
STUDY SITES…....................................................................................................... 79
STUDY DESIGN…................................................................................................... 80
Pitfall Trap Sampling…....................................................................................... 80
Sample Processing…........................................................................................... 80
Habitat Characteristics….................................................................................... 81
Landscape Characteristics................................................................................... 82
Management......................................................................................................... 83
STATISTICAL ANALYSES..................................................................................... 84
Functional Groups............................................................................................... 84
Abundance............................................................................................................ 84
Multi-model Inference.......................................................................................... 84
RESULTS...................................................................................................................... 86
Functional Groups................................................................................................ 86
Model Selection.................................................................................................... 87
DISCUSSION............................................................................................................... 88
Functional Groups............................................................................................... 89
Biogeographical Comparison.............................................................................. 90
Model Selection.................................................................................................... 92
Conclusion............................................................................................................ 94
LITERATURE CITED.................................................................................................. 96
TABLES AND FIGURES............................................................................................. 99
Chapter 4: DIVERSITY AND ABUNDANCE OF GROUND BEETLES
(COLEOPTERA: CARABIDAE) IN REMNANT TALLGRASS PRAIRIE
HAYMEADOWS......................................................................................... 119
Abstract.............................................................................................................. 119
INTRODUCTION....................................................................................................... 120