Loyola University ChicagoLoyola eCommons

Master's Theses Theses and Dissertations

2011

The River Continuum Redux: Aquatic Insect DietsReveal the Importance of AutochthonousResources in the Salmon River, IdahoKathryn VallisLoyola University Chicago

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This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.Copyright © 2011 Kathryn Vallis

Recommended CitationVallis, Kathryn, "The River Continuum Redux: Aquatic Insect Diets Reveal the Importance of Autochthonous Resources in theSalmon River, Idaho" (2011). Master's Theses. Paper 561.http://ecommons.luc.edu/luc_theses/561

LOYOLA UNIVERSITY CHICAGO

THE RIVER CONTINUUM REDUX:

AQUATIC INSECT DIETS REVEAL THE IMPORTANCE OF

AUTOCHTHONOUS RESOURCES IN THE SALMON RIVER, IDAHO

A THESIS SUBMITTED TO

THE FACULTY OF THE GRADUATE SCHOOL

IN CANDIDACY FOR THE DEGREE OF

MASTER OF SCIENCE

PROGRAM IN BIOLOGY

BY

KATHRYN LYNDSEY VALLIS

CHICAGO, ILLINOIS

DECEMBER 2011

Copyright by Kathryn Lyndsey Vallis, 2011

All rights reserved.

iii

ACKNOWLEDGEMENTS

Although the end result of a Master’s program is a degree celebrating an

individual’s achievement, the journey to get to that point is certainly not traveled alone. I

would first like to thank all of those that I had the privilege of working alongside in the

Rosi-Marshall lab at Loyola and the Cary Institute, particularly Dr. Heather Bechtold,

Holly Wellard Kelly, Dustin Kincaid, and Sarah Zahn Seegert, for their help with the

many and various aspects of this project, for their perspective and good humor, and for

their support and friendship both in and out of the lab. I would also like to thank Sylvia

Lee, for generously offering her time and diatom expertise when it was most needed.

I would also like to thank the Baxter lab at Idaho State University for their

accommodating and welcoming ways during the time I spent in Pocatello. I would

especially like to thank Jennifer Cornell, Kevin Donner, Hannah Harris, Jessica Lueders-

Dumont, Rebecca Martin, and Cameron Morris for teaching me the ways of the wild

West and for their help in the field and the lab. I must also thank Dr. G. Wayne Minshall,

for giving me access to the Idaho State University archives, and Dave Funk, for his insect

identification work and meticulously labeled specimen vials. This work was supported

by a grant from Idaho NSF-EPSCoR (EPS-0814387).

I would also like to thank the staff at the Cary Institute of Ecosystem Studies, for

facilitating my transition to New York and a new laboratory environment. I would

particularly like to thank Heather Malcolm and Deana Machtley for sharing their

iv

extensive scientific knowledge, lab space, and equipment, and for their continual

encouragement and support. I would like to thank Dr. David Strayer, for allowing me to

spend many microscope hours in his lab, and on his microscopes.

I’d also like to thank Dr. John Davis for all of the time and energy invested

toward me and this project, for his willingness to be a sounding-board and editor, for his

invaluable perspective, and for his constant encouragement and understanding.

I must also thank Dr. Colden Baxter for welcoming me into his lab at Idaho State

University, for his stream-side instruction and campfire-side tunes, and for his great

insight, thoughtful comments, and valued assistance throughout the course of this project.

I would like to thank my committee members Dr. Martin Berg, for his expertise in

all things aquatic insects and statistics, and for all of his time, effort, and support invested

in me and this project, and Dr. Christopher Peterson, for his help and constructive

remarks, for sharing his classroom with me, and for his assistance in the development and

writing of this work.

I thank my advisor, Dr. Emma Rosi-Marshall, for her endless enthusiasm, her

staunch support, her insightful contributions, and her constant guidance and

encouragement throughout my undergraduate and Master’s programs. For this, and for

all of the new experiences and incredible people I encountered as a result of her

mentorship and this project, I will always be thankful.

Finally, I must thank my family – especially my parents, George and Josephine,

and my brother, Christopher – and my friends for listening to me in times of exhilaration

and frustration, for offering invaluable advice and perspective, and for providing constant

v

and necessary reminders of the “bigger picture.” It was your support and love that saw

me through this journey, and I am incredibly grateful you were there to travel it with me.

To my parents, George and Josephine, and my brother, Christopher, for all of their love

and support. To the memory of my grandfather, Milton, who gave his family a place to

enjoy and appreciate all that our freshwater ecosystems have to offer.

No man ever steps in the same river twice…

Heraclitus

TABLE OF CONTENTS

ACKNOWLEDGEMENTS iii

LIST OF TABLES ix

LIST OF FIGURES x

ABSTRACT xii

CHAPTER ONE: INTRODUCTION 1

CHAPTER TWO: METHODS 6

Study sites 6

Taxa studied 9

Diet analysis 11

Statistical analysis 12

CHAPTER THREE: RESULTS 14

Community resource use and the predictions of the RCC 14

Functional feeding groups 17

Shredders 17

Collector-gatherers 18

Collector-filterers 18

Scraper-grazers 19

CHAPTER FOUR: DISCUSSION 26

The River Continuum Redux 26

Global climate change signals in macroinvertebrate diet composition 28

Functional feeding groups and gut content analysis 29

Facultative diet-switching may help stabilize food webs 32

Hidden treasures: Archived insects and the value of invertebrate

diet composition 33

Conclusions 35

LITERATURE CITED 36

VITA 44

ix

LIST OF TABLES

Table 1. Percent of (un-weighted) allochthonous (AL), autochthonous (AU),

amorphous detritus (AD), and animal (AN) materials in the diets of

individual taxa collected from Camp Creek (Site A) in summer and fall

1976 and 2009. 21

Table 2. Percent of (un-weighted) allochthonous (AL), autochthonous (AU),

amorphous detritus (AD), and animal (AN) materials in the diets of

individual taxa collected from Smiley Creek (Site B) in summer and fall

1976 and 2009. 22

Table 3. Percent of (un-weighted) allochthonous (AL), autochthonous (AU),

amorphous detritus (AD), and animal (AN) materials in the diets of

individual taxa collected from Obsidian (Site C) in summer and fall 1976

and 2009. 23

Table 4. Percent of (un-weighted) allochthonous (AL), autochthonous (AU),

amorphous detritus (AD), and animal (AN) materials in the diets of

individual taxa collected from Casino (Site D) in summer and fall 1976

and 2009. 24

x

LIST OF FIGURES

Figure 1. The Salmon River basin is located in central Idaho (inset). My sampling

sites were located in the upper Salmon River, in the Sawtooth National

Recreation area near Stanley, Idaho. Adapted from Minshall et al.

1982. 8

Figure 2. Allochthonous material in insect diets decreased downstream, while

autochthonous materials comprised a substantial amount of invertebrate

diets at all sites in both years. Stream order and catchment area increased

from Camp (A), the headwater site, to Casino (D). Community-weighted

data was used to show the consumption of allochthonous, autochthonous,

amorphous detritus, and animal material at each site in 1976 and 2009.

Percent of the community represented by analyzed taxa (based on

community data from Minshall et al. 1982), as well as sample size at

each site (n) are also indicated. 9

Figure 3. Variation in the proportion of (a) allochthonous materials (b)

autochthonous materials, and (c) amorphous detritus among individual

insect diets at each Salmon River, ID site in 1976 and 2009.

Consumption of all materials was similar at all sites in both years. 15

Figure 4. (a) Hypothetical changes in the presence of allochthonous resources and

autochthonous resources along the longitudinal gradient, as predicted by

the RCC: allochthonous resources should be highest in the headwaters,

decreasing downstream; autochthonous resources should increase

downstream. (b) Regression lines of allochthonous and autochthonous

resources in the diets of individual insects collected in 1976 and 2009

from the Salmon River, ID. Autochthonous material in diets is similar

across sites, and allochthonous material in diets decreases downstream;

however, consumption of allochthonous materials is not as dramatic as

originally predicted. 16

xi

Figure 5. Proportion allochthonous, autochthonous, amorphous detritus, and animal

materials found in the diets of (a) shredders, (b) collector-gatherers, (c)

collector-filterers, (d) scraper-grazers collected from the Salmon River, ID

in summer and fall 1976 and 2009. Overall, shredders consumed the most

allochthonous material, and autochthonous material was consumed by all

functional feeding groups (FFGs). In general, diets were similar across

sites, seasons, and years. 25

xii

ABSTRACT

Along a river network, changes in the physical characteristics of a stream –

changes articulated by the River Continuum Concept (RCC) – have been predicted to

influence stream food webs, particularly the resources supporting aquatic

macroinvertebrates. Although diets of macroinvertebrates can track resource availability

along the longitudinal gradient of streams, insect diets were not assessed in the original

RCC study; rather, insects were grouped into functional feeding groups (FFGs). In

addition, global climate change is increasing the frequency and spatial extent of wildfire

and beetle outbreaks throughout the western United States and could affect riparian

vegetation and the amount of allochthonous inputs entering the system. Based on gut-

content analysis of insects collected and archived from the Salmon River (SR), ID in

1976 and used in the development of the RCC, I first tested whether insect diets followed

the original predictions of the RCC. Based on the predictions of RCC, I predicted that

consumption of allochthonous inputs of terrestrial leaves would be greatest in the

headwaters and decline along the continuum. In addition, by resampling these sites in

2009, I assessed whether the relative importance of allochthonous and autochthonous

resources have shifted along this continuum, indicating potential shifts in riparian

vegetation since 1976. Insect diets in 1976 and 2009 were similar across years and

seasons, and these data did not indicate changes in riparian vegetation. In addition, insect

xiii

diets did not follow the predictions of the RCC, as SR insects consumed primarily

autochthonous material in the forested headwaters. Allochthony decreased along the

longitudinal gradient, as predicted by the RCC; however, this trend was not as dramatic

as predicted by FFGs alone. Insects in the headwaters, including the dominant shredder

Yoraperla (Insecta: Plecoptera), consumed mostly autochthonous material. Autotrophic

production, then, was shown to be an important food resource, even in this forested

headwater stream. As this reliance on autochthonous resources was high for those

invertebrates (e.g. shredders) thought to rely mostly on allochthonous material, my results

indicate the importance of gut content analysis and cautions against relying on FFGs to

explore which resources fuel stream food webs.

1

CHAPTER ONE

INTRODUCTION

The River Continuum Concept, developed by Vannote et al. (1980), provides a

framework by which one can predict biological, physical, and chemical changes along a

longitudinal gradient in stream systems. It was proposed that terrestrial and aquatic

ecosystems are inherently linked, as are downstream and upstream reaches (Minshall et

al. 1983, Vannote et al. 1980, Rosi-Marshall and Wallace 2002, Li and Dudgeon 2008),

and that the importance of these linkages can change along the continuum. While the

general applicability of the RCC has been debated (Thorp and Delong 1994 & 2002,

Statzner and Higler 1985, Li and Dudgeon 2008) and some elements have been amended

over time (Minshall et al. 1983), the general concept is still useful, especially in

temperate forested stream networks.

Drawing from observations and data collected from sites along a number of river

networks, the RCC proposes that to understand the biological dynamics of streams and

riverine systems, one must consider the gradient of physical factors formed by the

drainage network (Vannote et al. 1980). Based on the idea of dynamic equilibrium, the

authors propose that a stream ecosystem achieves a balance between the physical factors

– stream size, width, velocity, depth, sediment load – and the biological factors – primary

production, organism composition. Such shifts in the physical and chemical

characteristics of a stream are also reflected in resident macroinvertebrate assemblages of

2

stream systems. Aquatic insects are organized into functional feeding groups (FFGs)

based upon their behavioral and morphological adaptations for food acquisition

(Cummins 1973, Cummins and Klug 1979, Vannote et al. 1980). These groups include

shredders, collector-gatherers, collector-filterers, scraper-grazers, and predators. As food

resources shift along the longitudinal gradient of a river, the relative proportion of these

groups are also predicted to shift, reflecting food availability along the longitudinal

gradient (Wallace et al. 1997, Stone & Wallace 1998, Baer et al. 2001, Rosi-Marshall &

Wallace 2002). Specifically, headwater reaches in forested river networks are typically

heavily shaded, shallow, and cooler than downstream reaches. This riparian vegetation

can limit primary production and increase allochthonous inputs of coarse particulate

organic matter (CPOM, defined as organic matter >1mm), subsequently increasing the

reliance of macroinvertebrate consumers on terrestrial detritus (Vannote et al. 1980). As

macroinvertebrates in headwater streams consume this terrestrial input and convert it to

fine particulate organic matter (FPOM, defined as organic matter <1mm), it can increase

FPOM transport to downstream habitats, where organisms exploit this energy and to

maintain their productivity (Cummins et al. 1989, Vannote et al. 1980).

Although shifts in FFGs may be useful in determining the relative health of a

system, shifts in the diets of aquatic insects can provide even more insight into stream

function (Mihuc & Minshall 2005). However, FFG designation is confused with the

assumption that an insect definitively consumes a specific resource (e.g. all shredders eat

leaves). To the contrary, despite their FFG assignment, many insects have been found to

be generalist feeders (eating any abundant and available resource), or will switch

3

resources between seasons, during a disturbance event, or based on their developmental

stage (Cuffney & Minshall 1981, Mihuc & Minshall 1995, Wallace et al. 1997, Plague et

al. 1998, Rosi-Marshall & Wallace 2002). As a result, the diets of aquatic insects have

also been shown to track the availability of resources (Mihuc & Minshall 1995, Wallace

et al. 1997, Rosi-Marshall & Wallace 2002). Thus, the diets of aquatic insects should

reflect the available resources along the river continuum.

Analysis of the diets of aquatic insects could also provide insight into the effects

of disturbance on stream ecosystems, particularly changes in available food resources.

Global climate change (GCC), for example, has increased the frequency and spatial

extent of large-scale terrestrial disturbances (e.g., wildfire and beetle outbreaks)

(Westerling et al. 2003, 2006, Kurz et al. 2008). As a result, GCC may have

subsequently altered the structure of riparian vegetation and the relative importance of

allochthonous and autochthonous resources along the continuum. Such shifts may also

be reflected in the diets of insects along the river network. For instance, more frequent

wildfire that reduces riparian canopy cover may increase light flux to the stream surface,

increasing autotrophic production. In addition, reduced riparian cover may have

decreased inputs of terrestrial detritus, so that GCC may have increased the availability of

autochthonous resources along the continuum. Such habitat modifications linked to

global climate change have been observed in the western United States (Westerling et al.

2003, 2006, Kurz et al. 2008), and altered riparian vegetation may decrease allochthonous

inputs and increase in-stream production (Dwire & Kaufman 2003, Minshall 2003).

Accordingly, the diets of aquatic insects may track such changes, representing an

4

important tool for assessing how GCC may alter energy flows along the continuum.

Based on gut content analysis of specimens collected from Salmon River, ID sites

used in the testing of the RCC in 1976, I assessed whether aquatic insects in this system

followed the original predictions of the RCC. Based on these predictions, as well as

previous river continuum and diet analysis studies, I hypothesized that the diets of aquatic

insects collected in 1976 (archived specimens) and in 2009 would follow the predictions

of the RCC based on gut content analysis. That is, consumption of allochthonous

resources would be highest in the headwaters with consumption of autochthonous

resources increasing downstream. Second, the diets of aquatic insects would generally be

reflective of their FFG assignment (i.e. shredders would primarily consume leaf detritus

and grazers would consume algae). I also hypothesized that the diets of aquatic insects

from 1976 and 2009 would differ as a result of disturbances influenced by GCC,

specifically, increased incidence of fire and beetle kill would reduce the availability of

allochthonous resources in the headwaters (Mihuc & Minshall 2005). Thus, diet analysis

of aquatic insects from the past and present allowed me to be the first to actively test for

the predicted changes in resource use along the river continuum in 1976 (the original

RCC study) and 2009 (the RCC Redux study). It also allowed me to explore if aquatic

insect diets showed the effects of disturbances influenced by climate change in a three-

decade time span. To test my hypotheses, preserved specimens from the original RCC

study were obtained from Idaho State University’s archives. Aquatic insects were then

collected from the same RCC sites throughout summer and fall 2009, and individuals

from each site, season, and year were used for gut content analyses. These data provide

5

the first exploration of resource use in the Salmon River and examination of long-term

changes in resource use.

6

CHAPTER TWO

METHODS

Study sites

The Salmon River is located in the mountainous region of central Idaho (Figure

1). It flows 684 km from its headwaters to its confluence with the Snake River, making it

not only the largest tributary of the Snake, but also the longest free-flowing river in the

lower 48 States (Bureau of Land Management-Idaho 2010). Located in federally

designated wilderness areas, the Salmon River is unimpounded over its entire length and

has experienced minimal channelization, diversion, land use change, and anthropogenic

influence (Minshall et al. 1982). From its headwaters to its confluence with the Snake

River, there is an overall elevation drop of approximately 2000 m (Minshall et al. 1982).

Study sites were located in the Upper Salmon River basin in the Sawtooth

National Recreation Area near Stanley, Idaho in the Sawtooth Mountain Range of the

Idaho Rockies (Figure 1). Four sites were selected and sampled in 1976, with the

resulting data eventually used in the development and testing of the RCC (Vannote et al.

1980, Minshall et al. 1982, Minshall et al. 1983). We re-sampled these sites for the first

time in 2009. Distributed along 65 km of the river, the four sites were situated at the

headwaters of the Salmon River to just upstream of its confluence with the Yankee Fork

of the Salmon River (Minshall et al. 1982). Camp Creek (catchment area = 0.6 km2), a

second-order stream at approximately 2500 m elevation, served as the forested headwater

7

site (width of 1.1 m and a depth of 0.1 m) (Minshall et al. 1983). Fourth, fifth, and sixth-

order sites were also selected and are referred to as Smiley Creek, (catchment area = 40.6

km2, elevation: 2200 m), Obsidian (catchment area = 478.1 km

2, elevation: 2000 m), and

Casino (catchment area = 846. 3 km2, elevation: 1900 m). The stream width and depth of

Smiley is 6.3 m and 0.23 m, respectively. Stream width and depth of Obsidian and

Casino is 27.1 m and 0.39 m, and 42.9 m and 0.46 m, respectively (Minshall et al. 1983).

We were unable to sample at the exact location of the 1976 sampling at Obsidian in 2009,

due to expansion of the Sawtooth Fish Hatchery. As a result, we sampled approximately

50 m upstream of the original site, now the location of a water intake for the hatchery.

Camp Creek, Smiley Creek, Obsidian, and Casino will hereafter be referred to as Sites A,

B, C, and D, respectively, in regards to increasing stream order and catchment area from

A to D (e.g. Figure 2).

Snow accounts for the main source of precipitation from November to March and

enters the stream from about May to July (Minshall et al. 1983). Canopy cover was

greatest in the headwaters and progressively decreased downstream as the stream

widened. The riparian vegetation of the Upper Salmon River basin is largely dominated

by Pinus contorta (lodgepole pine), Pseudotsuga menziesii (Douglas fir), Salix sp.

(willow), and Populus tremuloides (quaking aspen) in the headwaters, with sagebrush

steppe ecosystem dominating the riparian zones of the lower sites. The Upper Salmon

River Basin has been affected by wildfire in recent years, and beetle kill has been

observed in riparian vegetation along our study reach (Bureau of Land Management-

Idaho 2010).

8

Figure 1. The Salmon River basin is located in central Idaho (inset). My sampling sites were

located in the upper Salmon River, in the Sawtooth National Recreation area near Stanley,

Idaho. Adapted from Minshall et al. 1982. Photo Credits: Satellite imagery: Google Earth

2011. Idaho/Salmon River Basin: USGS.

9

Taxa studied

During the original RCC sampling period, insects were collected from the Salmon

River in the summer (July) and winter (January) of 1976 were identified and categorized

by FFGs, data which were used in the development and testing of the RCC (Minshall et

al. 1982). A few specimens were also collected in September to November of 1976.

Aquatic invertebrates were sampled in 1976 as described by Minshall et al. (1982; 1983),

with insects collected on a single date in each season using a kick-net. Some of these

Figure 2. Allochthonous material in insect diets decreased downstream, while autochthonous

materials comprised a substantial amount of invertebrate diets at all sites in both years. Stream

order and catchment area increased from Camp (A), the headwater site, to Casino (D).

Community-weighted data was used to show the consumption of allochthonous (■),

autochthonous ( ), amorphous detritus (■), and animal material (■) at each site in 1976 and

2009. Percent of the community represented by analyzed taxa (based on community data from

Minshall et al. 1982), as well as sample size at each site (n) are also indicated.

10

specimens were archived at Idaho State University in the Stream Ecology Center’s

archives, and were viable for gut content analysis. Thus, although these insects were

collected from the Salmon River in 1976, their diet data was not examined until 33 years

later, in 2009. As only a limited number of taxa were archived, the number of taxa and

individuals used for gut content analysis was restricted to the specimens available from

the archived collection. The number of available taxa was highest for Camp Creek and

was more limited at downstream sites. Although preserved taxa were not consistently

available from Camp Creek to Casino, individuals used in the gut content analysis, in

general, comprised the majority of the macroinvertebrate assemblage (12%-65% of the

community; Figure 2). Samples collected in the summer (25-29 July 1976) and the fall

(23 September - 20 November 1976) were used to assess longitudinal patterns in insect

diets from the original RCC sampling data.

To assess whether potential shifts in terrestrial disturbance regimes (due to

wildfire or beetle kill) may have affected macroinvertebrate resource use, I collected

additional insect samples from each site in summer (July 16 to August 1) and fall

(September 29 to October 2) of 2009 using a coarse-mesh kick-net (800/900 µm) by

disturbing the substrate upstream of the net. Insects were preserved in Kahle’s solution

(Pennak 1978) in the field until the time of gut content analysis. Taxa were chosen for

diet analysis to provide both a means of comparison to the 1976 insects and a

longitudinal representation of present-day resource use from sites A to D. All individuals

were identified according to Merritt et al. (2008). When taxonomic classifications had

11

changed between the original 1976 sampling dates and 2009, recent taxonomic

classifications were used.

Overall, six shredder taxa, eleven collector-gatherer taxa, two collector-filterer

taxa, and three scraper-grazer taxa were analyzed in this study (Tables 1- 4). In total, gut

contents from twenty-two taxa preserved and/or found variably along the longitudinal

gradient were analyzed. Predators from 1976 and 2009 were excluded from this analysis,

as our main question concerned allochthonous and autochthonous resource use along the

river continuum and predators were presumed to have predominately animal material in

their diets (Minshall et al. 1982, Rosi-Marshall & Wallace 2002; personal observation).

Diet analysis

Gut content analysis was performed on individual insects collected in 1976 and

2009 (Benke & Wallace 1980). The foreguts of 1 to 15 individuals were dissected from

each taxon collected at each site in both years, depending upon availability. Gut contents

were sonicated and filtered onto 25mm, 0.45 um membrane filters that were then dried in

a drying oven at 60°C for at least 10 minutes. The dried filters were then affixed with

immersion oil to slides for gut content analysis. The number of individuals per slide

ranged from 1 to 5, based on the amount of material that was present in the individual

insects. Food particles were identified as leaf, wood, algae, amorphous detritus, fungi, or

animal, and ultimately assigned to the more general categories of allochthonous,

autochthonous, or amorphous detritus (Benke & Wallace 1980, Rosi-Marshall & Wallace

2002). The area of each food particle was then measured using ImageJ (National

12

Institutes of Health, Bethesda, Maryland, USA; http://imagej.nih.gov/ij/) to calculate the

relative proportion of food items in the diet(s) of those insect(s).

Statistical analysis

To assess how aquatic insect diets shifted along the longitudinal gradient and if

diets reflected FFG assignment, I grouped insects by FFG and compared their diets at

each sampling site. This comparison was based on both non-weighted diet data and

community weighted data. Using community composition data based on abundances

from Minshall et al. 1982, diet data were community-weighted to account for the relative

contribution of each taxa to the macroinvertebrate community of sites A-D and to

determine what proportion of the community was represented by the taxa analyzed

(Figure 2). Community-weighted data were used to compare seasonal resource use in

1976 and 2009 and explore the possibility of decadal shifts in the diets of aquatic insects.

Non-weighted data were used for statistical analyses to explore variation between sites

and individual taxa. To assess how diets shifted along the longitudinal gradient, I

compared the four FFGs (shredders, collector-gatherers, collector-filterers, and scraper-

grazers) at each site. Statistical analyses were used to analyze 2009 data; 1976 data were

precluded from statistical analyses due to insufficient sample size. I used statistical

analyses on the non-weighted seasonal 2009 data to explore diet differences between

seasons. 2009 allochthonous material diet data of each FFG and on the entire 2009

sampled community (p<0.05) were compared using one- or two-way ANOVAs in

SYSTAT, with site and season as the main effects. Site B was excluded from the

shredder and collector-filterer FFGs’ two-way ANOVA, due to lack of seasonal data

13

(Table 2). Separate one-way ANOVA were run on seasonal data to verify significance.

Only allochthonous material in gut contents was examined, as I was primarily concerned

with differences between allochthonous and autochthonous consumption, and the relative

proportions of the two resources are directly related to one another. When necessary, I

used the appropriate transformations (arcsine square-root) to meet statistical assumptions

(i.e. of ANOVA).

14

CHAPTER THREE

RESULTS

Community resource consumption and the predictions of the RCC

Overall, diets of individuals collected in 1976 and 2009 were similar between

years and across seasons (when samples were available and such a comparison could be

made) (Figure 2). However, in both years, the relative importance of allochthonous

materials in diets was significantly different among sites (F= 5.29, p=0.002, df=3),

whereby it was greatest at Camp Creek and decreased along the longitudinal gradient

(Figure 3a). Allochthonous materials in the diets of headwater insects were substantially

lower than the predicted presence of allochthonous resources in the headwater streams

(Figure 4a and b), representing about 40% of the overall diet. Similarly, insects in the

headwaters consumed large amounts of autochthonous materials (Fig. 3b). This pattern

was similar across all sites (Figure 3b) and was substantially greater than what was

predicted from the RCC (Fig. 4a and b). Amorphous detritus was found in similar

amounts in diets from sites B to D, with the lowest amounts of amorphous detritus found

in gut contents of insects collected from site A, Fall 2009 (Figure 3c, 4a, and 4b).

Consumption of animal material was highest at sites C and D in both seasons, mostly due

to the large amounts of animal material in the guts of the filter-feeding trichopteran

Brachycentrus (Tables 3 & 4).

15

Figure 3. Variation in the proportion of (a) allochthonous materials (b) autochthonous

materials, and (c) amorphous detritus among individual insect diets at each Salmon River, ID

site in 1976 (■) and 2009 (■). Consumption of all materials was similar at all sites in both

years. Sites are arranged from most upstream (Camp – A) to most downstream (Casino – D).

The solid line indicates the median, and the dotted line represents the mean. Dots indicate 5%

and 95% percentiles and whiskers show the range of data. The absence of whiskers or dots is

due to insufficient data.

16

Camp (A) Smiley (B) Obsidian (C) Casino (D)

% r

eso

urc

e found

in a

qua

tic insect die

ts

0

20

40

60

80

100

b Camp (A) Smiley (B) Obsidian (C) Casino (D) e

% p

resence o

f re

sourc

e p

redic

ed b

y R

CC

0

20

40

60

80

100a)

b)

Figure 4. Sites are arranged from most upstream (Camp – A) to most downstream (Casino –

D). (a) Hypothetical changes in the presence of allochthonous resources ( ) and

autochthonous resources ( ) along the longitudinal gradient, as predicted by the RCC:

allochthonous resources should be highest in the headwaters, decreasing downstream;

autochthonous resources should increase downstream. (b) Regression lines of allochthonous

(▬) and autochthonous (▬) resources in the diets of individual insects collected in 1976 and

2009 from the Salmon River, ID. Autochthonous material in diets is similar across sites, and

allochthonous material in diets decreases downstream; however, consumption of allochthonous

materials is not as dramatic as originally predicted. Dotted lines in 2b represent 95%

confidence intervals.

17

In terms of the community-weighted data comparisons, trends were similar

between 1976 and 2009 (Figure 3). Insects analyzed represented 12% (site D) to 65%

(site A) of the community in 1976, to 66% (site C) to 86% (site A) of the community in

2009; in all cases but one (i.e. site D in 1976), the majority of the assemblage was

sampled and analyzed. In diets, allochthonous material was highest in the headwaters

and decreased downstream, and autochthonous material was an important resource for the

macroinvertebrate community at all sites in both years (Figure 2), in a pattern loosely

reflective of the RCC’s predicted changes in the proportion of dominant resources along

the longitudinal gradient.

Functional feeding groups

Shredders

Compared to other FFGs, shredders consumed the most allochthonous material,

but they still relied substantially on autochthonous material, even in the most upstream

sites (sites A and B). Reliance on allochthonous material did not differ significantly

between sites (F=0.499, p-value=0.687, df=3) or seasons (F=3.81, p-value =0.062, df=1).

At least half of the shredder diets were composed of autochthonous material and

amorphous detritus, and this reliance did not appear to differ with sampling site.

Moreover, this overall reliance did not differ between 1976 and 2009.

Despite the overall trend in FFG diets, the relative reliance on allochthonous and

autochthonous material varied among taxa. Allochthonous material comprised roughly

half to the entire diet composition of Zapada, Eucapnopsis, and Capnia in 1976 and

2009, but the dominant headwater shredder, Yoraperla, consumed primarily algal

18

material (Table 1). In 1976, autochthonous material accounted for 69% of Yoraperla

diets (20% allochthonous) and 66% in 2009 (21% allochthonous). The sole shredder taxa

found at C and D in 2009, Pteronarcys, consumed 51% and 70% allochthonous material

at each site. Animal material also comprised a portion of their diets, particularly at site C

(27%) (Table 3).

Collector-gatherers

The diets of collector-gatherers were primarily composed of amorphous detritus

and autochthonous materials (Figure 5b), with limited contribution of allochthonous

material. This overall trend did not differ between 1976 and 2009 (Figure 2, Figure 3).

Although allochthonous material in the diets of collector-gatherers did not differ between

seasons (F=2.92, p=0.092, df=1), reliance on allochthonous material varied with

sampling location, whereby collectors consumed more allochthonous materials at site A

than at downstream sites (F= 4.72, p=0.005, df=3). Reliance on amorphous detritus and

autochthonous material was similar between sites. Despite these similarities in the

overall diets of collector-gatherers, diets did vary at the genera-level. Ephemerella

consumed the greatest amount of allochthonous materials at site A: 58% in fall 1976 and

69% in summer 2009 (Table 1). At the downstream sites, the closely related Drunella

(4%) and Serratella (8%) ate primarily autotrophic material and amorphous detritus

(Tables 2-4).

Collector-filterers

Collector-filterers exhibited high variability in the composition of their diets, but

in general had the highest amount animal material compared to other FFGs.

19

Allochthonous material in diets differed significantly across sites (F=5.70, p=0.004,

df=3), with significantly higher amounts of allochthonous material consumed at site A.

However, consumption of allochthonous material was not significantly different between

seasons (F=0.792, p=0.382, df=1). In 1976 and 2009, diets of Simulium at site A, the

only headwater collector-filterer analyzed, included 32% allochthonous materials

annually (Table 1). In simulid diets, allochthonous material in summer 2009 was not

significantly different across sites (F=2.30, p=0.194, df=3). Simulium gut contents

contained some animal material, and Brachycentrus diets included high amounts of

animal material (Tables 3 & 4). Collector-filterer diets at site C in 1976 differed from

those in 2009, with autochthonous material accounting for 73% of 1976 diets and animal

material comprising 65% of the 2009 collector-filters (Figure 2). This may be due, in

part, to Brachycentrus’ contribution of animal materials to the FFG collector-filterer

analysis, and the fact that Simulium was the only 1976 collector-filterer taxa available for

analysis at site C. At site D, allochthonous, autochthonous, and animal materials and

amorphous detritus were found in similar amounts in Brachycentrus gut contents (Table 3

& 4).

Scraper-grazers

The dominant resources comprising scraper-grazer diets were amorphous detritus

and autochthonous materials in similar proportions (Figure 5d), with limited contribution

of allochthonous material. Consumption of allochthonous materials was not significantly

different among sites (F=2.30, p=0.091, df=3), but did differ significantly between

seasons (F=4.96, p=0.032, df=1), with higher amounts of allochthonous materials

20

consumed in the fall. A comparison between scraper-grazer diet compositions in 1976

and 2009 was only possible at sites A and C. At site A in summer 1976, scraper-grazers

diets were comprised primarily of autochthonous materials and amorphous detritus

(Figure 5d). At site C in summer 1976 and 2009, the presence of allochthonous materials

in the gut contents of scraper-grazer was similar (5% and 8% respectively), but

consumption of autochthonous resources and amorphous detritus differed between the

two summers (Figure 5d, Table 3). Unlike the previous FFGs, consumption of

allochthonous materials by scraper-grazers was highest at site A only in summer 1976

(36%); the greatest amount of allochthonous materials was found in the diets of scraper-

grazers at site D in fall 2009 (42%).

21

Table 1. Percent of (un-weighted) allochthonous (AL), autochthonous (AU), amorphous

detritus (AD), and animal (AN) materials in the diets of individual taxa collected from Camp

Creek (Site A) in summer and fall 1976 and 2009. - - indicates unavailable data.

22

Table 2. Percent of (un-weighted) allochthonous (AL), autochthonous (AU), amorphous

detritus (AD), and animal (AN) materials in the diets of individual taxa collected from Smiley

Creek (Site B) in summer and fall 1976 and 2009. - - indicates unavailable data.

23

Table 3. Percent of (un-weighted) allochthonous (AL), autochthonous (AU), amorphous

detritus (AD), and animal (AN) materials in the diets of individual taxa collected from

Obsidian (Site C) in summer and fall 1976 and 2009. - - indicates unavailable data.

24

Table 4. Percent of (un-weighted) allochthonous (AL), autochthonous (AU), amorphous

detritus (AD), and animal (AN) materials in the diets of individual taxa collected from Casino

(Site D) in summer and fall 1976 and 2009. - - indicates unavailable data.

25

Figure 5. Sites are arranged from most upstream (Camp – A) to most downstream (Casino –

D). Proportion allochthonous (■), autochthonous ( ), amorphous detritus (■), and animal (■)

materials found in the diets of (a) shredders, (b) collector-gatherers, (c) collector-filterers, (d)

scraper-grazers collected from the Salmon River, ID in summer and fall 1976 and 2009.

Overall, shredders consumed the most allochthonous material, and autochthonous material was

consumed by all functional feeding groups (FFGs). In general, diets were similar across sites,

seasons, and years. Striped bars with “NA” indicate the absence of data. The * in (a) Camp

(A) F’76 represents the diet of one individual Capnia (Plec.).

26

CHAPTER FOUR

DISCUSSION

The River Continuum Redux

My results provide evidence that longitudinal patterns in macroinvertebrate diets

in the Salmon River are not consistent with the predictions of the RCC regarding changes

in dominant resources (Figure 4a and b). The RCC predicts that allochthonous resources

will support organisms in the headwaters and autochthonous resources will increase as

the river widens along the longitudinal gradient, peaking in mid-order reaches (Vannote

et al. 1980). However, gut content analysis of archived and present-day insects revealed

a different pattern. Although allochthonous resources were consumed in the greatest

amounts at the headwater site – an observation seemingly corresponding with the

predictions of the RCC – consumption of allochthonous materials was not as dramatic as

described in the RCC (Figure 4a and b), especially given that the dominant shredder

(Yoraperla) was highly algivorous. Although allochthonous inputs should be highest in

autumn when availability of leaf material is the highest, consumption of allochthonous

material was similar in the summer and post-leaf fall in 2009. Thus, this resource is

apparently not supporting macroinvertebrates to the extent that was originally presumed,

possibly due to a lack of retention of detrital resources (Minshall et al. 1992, Entrekin et

al. 2007, McNeely et al. 2007).

In contrast, autochthonous resources supported macroinvertebrate food webs at all

27

sites, in both years and seasons (Figure 2). These data, in conjunction with other studies

(Minshall 1978, Mayer & Likens 1987, Rosenfeld & Roff 1991, Thorp & Delong 1994 &

2002, McCutchan & Lewis 2002, McNeely et al. 2007), provide empirical evidence that

the importance of autochthony may be underestimated in stream ecosystems, particularly

in the headwaters (but see Vannote et al. 1980). The headwaters are presumed to have the

largest amounts of detrital material available to the macroinvertebrate community

(Vannote et al. 1980) and have been shown to support macroinvertebrate food webs in

some river basins (Rosi-Marshall & Wallace 2002). However, the diets of aquatic insects

collected in the headwaters of the Salmon River contained autochthonous material and

this resource often far exceeded the amount of allochthonous material consumed (Figure

3). Although not predicted by the RCC, macroinvertebrates in the headwaters may be

supported by algae (McNeely et al. 2007) particularly algae that are adapted to low-light

conditions. In addition, algae are considered to be a higher quality food resource than

detrital material (McNeely et al. 2007); in the presence of a thriving algal community,

aquatic insects may preferentially consume algae if possible, regardless of their FFG

classification. Thus, in the Salmon River, algae are not only a high quality food resource,

but are also fairly abundant, making it a viable food resource for much of the

macroinvertebrate community. Indeed, Minshall et al. (1983) reported that periphyton

chl-a was fairly high at all sites, and particularly high at the headwater site. Algal

resources appear to be extremely important to the Salmon River food webs and are of

greater importance in the headwaters than originally predicted by the RCC.

28

Global climate change signals in macroinvertebrate diet composition

Results from this study did not reveal a substantial shift in diet composition

between 2009 and 1976. This was contrary to my original prediction that more frequent

disturbances (e.g. fire) or increased unpredictability and severity of disturbance events

(e.g. flooding) associated with climate change would reduce riparian cover and the diets

of aquatic insects, particularly those in the headwaters (Dwire & Kaufman 2003,

Minshall 2003, Mellon et al. 2008). However, as insects in the Salmon River generally

appeared to be facultative feeders, this may have been a confounding factor in detecting a

climate signal. Additionally, insects may have preferentially been feeding on high-quality

algal material rather than potentially lower-quality detrital material (Ward & Cummins

1979, McNeely et al. 2007), even if it was not as readily available in 1976. If the

community was affected by environmental change, though, inflexible diets may have

caused the loss of certain taxa, leaving only generalist feeders to persist. Conversely,

riparian vegetation along the Salmon River simply may not have shifted to an extent that

may currently be measureable; therefore, a diet signal would not be expected to exist.

Because insect diets typically track resource availability (Cuffney & Minshall 1981,

Rosi-Marshall & Wallace 2002, McNeely et al. 2007), future comparisons of insect diets

to the data presented here may be useful.

Shifts in community composition associated with wildfire and loss of riparian

cover (Mihuc & Minshall 1995, Stone & Wallace 1998) have been observed in other

stream ecosystems, suggesting the potential for similar shifts associated with GCC-

induced shifts in these disturbance regimes (Mihuc & Minshall 1995, Stone & Wallace

29

1998, Gresswell 1999, Mihuc & Minshall 2005). Although I did not see shifts in overall

invertebrate diets, these disturbances may have altered the community composition of

macroinvertebrates. Analysis of community composition may provide additional insight

into how disturbances related to climate change affect invertebrate dynamics in the

Salmon River. My data on diets of macroinvertebrates collected 33 years apart provide a

strong framework upon which to develop hypotheses about which taxa may be sensitive

to change. For instance, some shredder taxa in the Salmon River headwaters consistently

ate leaves (i.e. Capnia and Eucapnopsis, Table 1); therefore, one may predict that these

taxa may be sensitive to changes in the amounts of allochthonous input or retention that

may occur as a result of climate change. Conversely, Yoraperla, which ate primarily

diatoms, and Zapada, which exhibit facultative plasticity (Mihuc & Minshall 1995), may

not be sensitive indicators.

Functional feeding groups and gut content analysis

In general, using FFGs to classify insects is useful inasmuch as they are used to

classify modes of feeding. FFGs should not be expected to accurately reflect of actual

resource consumption, nor should they be used as a replacement for gut content analysis

or stable isotope analysis when describing food webs. Previous studies have found that

FFGs are not reliable predictors of food resources consumed for many aquatic insects

(Benke & Wallace 1997, Mihuc & Minshall 1995, Plague et al. 1998, Rosi-Marshall &

Wallace 2002). Although some invertebrates can exhibit inflexible dietary preferences

(Eggert et al. 2003), other insects can be opportunistic feeders, exhibiting functional

plasticity and are capable of switching resources in the face of environmental

30

perturbation or disturbance (Mihuc & Minshall 1995; Dangles 2002). Possessing the

capacity to switch resources could provide a source of stability in an otherwise changing

ecosystem.

Similar to other studies, I hypothesized that invertebrate diets reflect functional

feeding group classification, (e.g. shredders consume mainly leaf material and grazers

consume mainly autotrophs) (Vannote et al. 1980). Although this was the case for a few

taxa, as has been found in prior studies (Cummins et al. 1973, Mihuc & Minshall 1995,

Baer et al. 2001), functional feeding group classification does not accurately predict diet

composition. In contrast to the predictions of the RCC, generalist feeders may be more

common along the continuum than insects that typify their assigned FFG than initially

thought “because mouthpart specialization does not necessarily indicate obligate resource

utilization” (Mihuc & Minshall 1995, Minshall 1988, Palmer et al 1993, Hall & Meyer

2008). That is, some insects may not be limited to a specific resource, despite their

morphology. For example, I found that shredders in the headwaters consumed large

amounts of autochthonous material in 1976 and 2009 (Figure 2, Table 1). Shredders ate

the most leaf material of all FFGs, but they still consumed large amounts of

autochthonous resources (Figure 5). Some shredder taxa (i.e. Capnia and Eucapnopsis)

ate large amounts of allochthonous material (Table 1), but the dominant shredder,

Yoraperla consumed primarily diatoms in 1976 and 2009. Previous studies have

demonstrated that Yoraperla consume detrital material (Dudley & Anderson 1982,

Hughes et al. 1999), but this study suggests they are facultative detritivores. The reliance

on autochthonous resources throughout the Salmon River by multiple FFGs strongly

31

indicates the potential problems of relying on FFGs to predict which resources support

macroinvertebrate food webs.

The diets of collector-gatherers, collector-filterers, and scraper-grazers were

similar among sites and between years, with autochthonous resources supporting the food

web. In addition, amorphous detritus was frequently consumed throughout the basin,

with the highest amounts found in diets from sites B, C, and D. Consumption of

amorphous detritus has been shown to increase along the longitudinal gradient in the

Little Tennessee River (Rosi-Marshall & Wallace 2002). Animal material was an

important resource at site D, which was primarily due to the influence of Brachycentrus,

a collecting-filtering trichopteran. According to Minshall et al. (1983), Brachycentrus

made 30% of the community composition at site D. Brachycentrus are generally

omnivores, grazing on algae and detritus from rocks and collecting seston from the water

column with their legs (Ross & Wallace 1981). It has been suggested that, due to the

structure of their highly-specialized legs, Brachycentrus is best suited to capture large

particles (e.g. animal material) from the water column, which would account for the large

amount of animal material found in their gut contents (Ross & Wallace 1981).

Food switching has been observed in many taxa analyzed in this study, including

Baetis, Drunella, and Zapada (Mihuc & Minshall 1995, Dangles 2002). Functional

plasticity is a common occurrence among aquatic insects, particularly in the event of

environmental disturbance (e.g. post-fire streams). Diet composition of 1976 and 2009

insects was similar among FFGs, sites, and seasons, which many indicate that many taxa

32

in the Salmon River are opportunistic feeders capable of facultative plasticity. In contrast

to other studies, these insects exhibited facultative plasticity under natural conditions.

Facultative diet-switching may help stabilize food webs

Opportunistic feeders that are tolerant of a wide range of conditions are well-

suited to surviving and thriving in the event of disturbance will help to provide stability

to a disturbed system (Mihuc & Minshall 1995, Gresswell 1999). Although assessments

of food web stability were beyond the scope of my study, theoretical and empirical

evidence suggests that my gut content results may provide insight into the potential

stability of the macroinvertebrate food web in the Salmon River. In the event of dramatic

changes to riparian vegetation (changes which may occur as a result of global climate

change), the biotic community, particularly in the headwaters, could be greatly affected.

However, if the macroinvertebrate community is composed of insects capable of

functional plasticity, those insects may not only survive, but thrive (Mihuc & Minshall

1995). Insects that are restricted in regards to food resources are more vulnerable and far

less resilient in the face of major environmental changes (Mihuc & Minshall 2005).

Indeed, dynamic food webs tend to encourage stability in an ecosystem (McCann 2000).

A food web composed solely of invertebrates with inflexible diets may be less likely to

persist when confronted with disturbances such as fire and beetle kill of riparian

vegetation. However, as has been demonstrated with Yoraperla in this study, more

insects may be capable of food switching than originally thought. This may indicate that

taxonomic diversity in post-disturbance streams may be more resilient than expected

(Stone & Wallace 1998), and taxa diversity has been shown to lend to the stability of a

33

system (McCann 2000); however, in such a potentially stressed system, there are

obviously other factors that must be considered (e.g. competition, changing stream

habitat). Regardless, in the western United States, where observable effects of climate

change are beginning to be recorded (Westerling et al. 2003, 2006, Kurz et al. 2008),

these opportunistic insects may eventually play an important role in contributing to a

thriving post-disturbance macroinvertebrate community and, in turn, the stability of the

stream ecosystem.

Hidden treasures: Archived insects and the value of invertebrate diet composition

While archived animal specimens, including organisms from fish to snakes, are

commonly utilized in diet composition analysis (Rodriguez-Robles 1998, Vander Zanden

et al. 2003, Shirey et al. 2008, Lavoie & Campeau 2010), this is, to my knowledge, the

first study to analyze the gut contents of archived aquatic insects. The ability to analyze

the diets of archived macroinvertebrates is an important tool when trying to determine the

effects of short or long-term environmental changes. It is also especially useful in the

event that isotope analysis is not possible, as was the case in this study. There were two

factors which precluded the use of isotope analysis in this study. First, isotope analysis

requires the destruction of the specimen in order to analyze it. As there were so few

archived 1976 taxa to begin with, the destruction of rare specimens and the resulting

depletion of the RCC archives were not feasible in this study. Second, the preservation

of the archived specimens may have affected the accuracy of isotope analysis. The 1976

specimens were first preserved in formalin, and some were later moved to ethanol for

long-term storage. Formalin is known to influence C and N isotopes (Hobson et al. 1997,

34

Bosley & Wainright 1999, Kaehler & Pakhomov 2001), although other studies have

found such effects to be negligible (Edwards et al. 2002) or correctable (Sarakinos et al.

2002). In addition, we were unable to definitively ascertain how the 1976 specimens

were prepared prior to preservation and subsequently treated in the years following.

Certain methods of preparation (i.e. acidification) have been shown to affect N (Jardine et

al. 2003, Jacob et al. 2005). Because of these factors, isotope analysis was not viable.

Such issues are not unique to this study; rather, they are issues that many

investigators may encounter when using archived specimens for diet composition

analysis. Museum specimens may be rare and therefore inappropriate to destroy, or the

means of preparation or preservation may interfere with isotope analysis. In light of

these issues, the advantage of gut content analysis when examining diet composition is

clear. Gut content analysis does not require destruction of the entire specimen, nor does

the type of preservative affect the analysis. The digestive tract of the specimen must be

sacrificed, but the rest of the specimen will mostly remain intact. Gut content analysis

also allows the investigator to see and measure the actual food resources in an

individual’s diet (Rosi-Marshall & Wallace 2002, Vander Zanden et al. 2003, Cross et al.

2007). Archived specimens, then, are not only important in their own right, but

individual specimens are also essentially archives in and of themselves. Insects, such as

those in this study, are collectors of diatoms and fungi and, much like diet composition

and macroinvertebrate community composition, diatom community composition may be

a sensitive indicator of environmental change (McCormick & Cairns 1994, Gregory-

Eaves et al. 1999, Saros et al. 2003). In this study, diatom community composition in

35

1976 was similar to 2009 in the Salmon River (Sylvia Lee, Personal correspondence,

2011). Of course, when possible, gut content analysis and isotope analysis used in

conjunction with one another may provide more insight into food resource utilization

than either analysis used alone.

Conclusions

Gut content analysis showed that diets did not follow the predictions of the RCC

and, in addition, FFGs did not prove to be reliable indicators of resources consumed.

Although the implementation of the RCC and FFGs in examining stream ecosystems and

the relative importance of basal resources may be useful in principle, they may be

misleading when used alone. Broad generalizations based on the RCC and FFGs may

lead us to underestimate the importance of certain resources in stream ecosystems and

should be used with caution. In contrast, gut content analysis can provide useful insights,

and such analyses are critical in understanding energy flow in an ecosystem.

Comparisons between past and present-day specimens can provide a means of

establishing long-term data sets. Although I was unable to detect a climate signal in this

study, long-term data sets may reveal the effects of environmental changes on stream

ecosystems. Care must be taken to consider other factors (e.g. extent of change over

time, individual characteristics of a system) when using diet analysis to detect signals of

change. Diet analysis and archived specimens can be important tools in exploring energy

flow and the effects of environmental change on ecosystems, particularly in the changing

global environment in which we live today, and especially when these changes span

multiple decades.

36

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44

VITA

Kathryn Vallis was born and raised in Calumet City, Illinois. After graduating

from Marian Catholic High School in 2003, she enrolled at Loyola University Chicago.

There, she volunteered in Dr. Emma Rosi-Marshall’s lab, sorting and identifying

caddisflies for a graduate research project. She graduated with a Bachelor of Science in

Biology with a minor in English in May 2007.

In fall 2008, Kathryn received a Teaching Assistantship at Loyola University

Chicago, where she began her Master’s thesis research investigating resource use of

aquatic insects, under the direction of Dr. Emma Rosi-Marshall. She served as a teaching

assistant for two semesters at Loyola University Chicago and participated in the

Fundamentals of Ecosystem Ecology course at the Cary Institute of Ecosystem Studies in

January 2009. Kathryn spent the summer of 2009 collecting insects and working on the

Salmon River, Idaho, with Dr. Colden Baxter and the Idaho State University Stream

Ecology Center. In January 2010, she moved with the Rosi-Marshall lab to the Cary

Institute of Ecosystem studies, where she finished her thesis work. Kathryn received the

“Best poster presentation in applied research (2009)” and “Best oral presentation in

applied research: Runner-up (2010)” awards and the “President’s Endowment Award

(2011)” from the North American Benthological Society for her Master’s work.