The Evolution of Phenotypic Variation in Anabrus Simplex

THE EVOLUTION OF PHENOTYPIC VARIATION IN ANABRUS SIMPLEX

(ORTHOPTERA: TETTIGONIIDAE): SHAPE DIFFERENCES IN MORPHOLOGY AND

PATTERNS OF MORPHOLOGICAL INTEGRATION IN MORMON CRICKETS

A thesis submitted

to Kent State University in partial

fulfillment of the requirements for the

degree of Master of Science

Stacy Rae Neal

August, 2009

Thesis written by

Stacy Rae Neal

B.A., The State University of New York, Stony Brook, 2003

M.A., Kent State University, 2009

Approved by

______, Dr. Patrick Lorch, Advisor, Department

of Biological Sciences

______, Dr. James Blank, Chair, Department of

Biological Sciences

______, Timothy Moerland, Dean, College of Arts

and Sciences

TABLE OF CONTENTS

ACKNOWLEDGEMENTS…………………………………………………………...vii

LIST OF FIGURES……………………………………………………………………iv

LIST OF TABLES……………………………………………………………………..vi

CHAPTER

I. Introduction…………………………………………………………………1 Natural History of Anabrus simplex (Orthoptera:Tettigoniidae)……...... 1 Techniques for Investigating Shape Differences in Morphology and Morphological Integration………………………………………………6 Materials and Methods………………………………………………...... 7 The Contact Call Hypothesis for Cohesive Movement in Mormon crickets…………………………………………………………………10

II. A Preliminary Study of Morphology in Mormon Crickets………………..12 Introduction…………………………………………………………….12 Methods………………………………………………………………...14 Results………………………………………………………………….18 Discussion………………………………………………………………25

III. Shape differences in Morphology in Mormon Crickets…………………....28 Introduction……………………………………………………………...28 Study Questions………………………………………………………....30 Methods………………………………………………………………….33 Results: Principal Component Analysis………………………………....39 Results: Shape Differences Between BF and NBF Mormon crickets…...48 Results: Shape Differences Between Three Population Types…………..54 Results: Correlations Between Morphology and Movement Rate………59 Discussion………………………………………………………………..64

IV. Patterns of Morphological Integration in Mormon Crickets……………….75 Introduction………………………………………………………………75 Study Questions………………………………………………………….78 Methods…………………………………………………………………..83 Results…………………………………………………………………....84 Discussion………………………………………………………………..87

V. Conclusion…………………………………………………………………….93

iii

LITERATURE CITED…………………………………………...... 100

LIST OF FIGURES

Figure 1.1……………………………………………………………………………….3

Figure 1.2……………………………………………………………………………….4

Figure 2.1………………………………………………………………………………15

Figure 2.2………………………………………………………………………………16

Figure 2.3………………………………………………………………………………17

Figure 2.4………………………………………………………………………………20

Figure 2.5………………………………………………………………………………21

Figure 2.6………………………………………………………………………………22

Figure 2.7………………………………………………………………………………23

Figure 3.1………………………………………………………………………………35

Figure 3.2………………………………………………………………………………35

Figure 3.3………………………………………………………………………………36

Figure 3.4………………………………………………………………………………36

Figure 3.5………………………………………………………………………………37

Figure 3.6………………………………………………………………………………37

Figure 3.7………………………………………………………………………………38

Figure 3.8………………………………………………………………………………38

Figure 3.9………………………………………………………………………………41

Figure 3.10……………………………………………………………………………..45

iv Figure 3.11……………………………………………………………………………..50

Figure 3.12……………………………………………………………………………..51

Figure 3.13……………………………………………………………………………..52

Figure 3.14……………………………………………………………………………55

Figure 3.15……………………………………………………………………………56

Figure 3.16……………………………………………………………………………57

Figure 3.17……………………………………………………………………………57

Figure 3.18……………………………………………………………………………60

Figure 3.19……………………………………………………………………………61

Figure 3.20……………………………………………………………………………62

Figure 3.21……………………………………………………………………………63

v LIST OF TABLES

Table 2.1………………………………………………………………………………24

Table 2.2………………………………………………………………………………24

Table 2.3………………………………………………………………………………24

Table 2.4………………………………………………………………………………24

Table 2.5………………………………………………………………………………24

Table 3.1………………………………………………………………………………32

Table 3.2………………………………………………………………………………43

Table 3.3………………………………………………………………………………43

Table 3.4………………………………………………………………………………43

Table 3.5………………………………………………………………………………44

Table 3.6………………………………………………………………………………44

Table 3.7………………………………………………………………………………46

Table 3.8………………………………………………………………………………47

Table 3.9………………………………………………………………………………47

Table 3.10……………………………………………………………………………..47

Table 3.11……………………………………………………………………………..48

Table 3.12……………………………………………………………………………..53

Table 3.13……………………………………………………………………………..58

Table 3.14……………………………………………………………………………..64

Table 4.1………………………………………………………………………………86

Table 4.2………………………………………………………………………………87

vi ACKNOWLEDGEMENTS

This thesis would not have been possible without Dr. Patrick Lorch, his invaluable experience with Mormon crickets in the field, or his lab resources. I would like to especially thank Dr. Christopher Vinyard whose expertise and guidance were also essential to the completion of this project, and Dr. Mark Kershner, who also provided guidance as a committee member. Many thanks to Dr. Darryl Gwynne and Dr. Kevin

Judge of the University of Toronto for providing a large dataset of Mormon cricket morphometrics for the analyses in Chapter 2. Bob Srygley and Laura Senior provided assistance with radio tracking the Mormon crickets in Eagle Rock, NV in 2008. Justin

Reeves provided helpful comments on the thesis. Dr. Richard Meindl assisted with some of the multivariate statistics used in this thesis. I would also like to thank my parents,

Cindy and Tim Fahey who have been so helpful, especially regarding my academic pursuits. Lastly, Orin Neal was extremely supportive throughout the process of completing this thesis and I also thank him for his encouragement to proceed with my studies in evolutionary biology.

vii CHAPTER I: INTRODUCTION

NATURAL HISTORY OF ANABRUS SIMPLEX (ORTHOPTERA: TETTIGONIIDAE)

Tettigoniidae is a large and diverse family of insects in the order Orthoptera.

Other Orthopterans include the grasshoppers, locusts, and crickets, and the Tettigoniidae

are known as katydids or bush-crickets. Males and some female tettigoniids are capable

of song production via stridulation of the wings which feature sound producing organs.

Calling in katydids is presumed to be a courtship display, possibly the sole method of mate finding or mate attraction, and song complexity is likely to have evolved under pressures including predation avoidance and sexual selection (Bailey & Rentz 1990).

The Tettigoniinae are the shield-backed katydids and there are roughly 500 species in this

subfamily that inhabit temperate or tropical environments (Bailey & Rentz 1990).

Anabrus simplex (Orthoptera: Tettigoniidae) are flightless North American shield- backed katydids commonly called Mormon crickets that exist with a broad distribution of phenotypes. Body size, coloration, daily movement, calling behavior, and mating structure are among the known differences between population types (Gwynne 1981,

Lorch & Gwynne 2000, Gwynne 2001, Bailey et al 2005, Bailey et al 2007a, Bailey et al

2007b). Populations of Mormon crickets are typically classified as either gregarious or

solitary based on estimates of population density, however, these terms also tend to be

synonymous with band-forming or non-band-forming behavior which can be quantified

1 2

using radio telemetry (Lorch & Gwynne 2000, Gwynne 2001, Bailey et al 2005).

Mormon crickets are referred to here as band-forming (BF) or non-band-forming (NBF) depending on estimated relative population density and movement behavior recorded by radio telemetry. Mormon crickets that are intermediate to the typical population types in these characteristics are referred to here as intermediate. Recent studies of mtDNA in

Mormon crickets revealed a genetic division that generally corresponds to eastern NBF and western BF population types that appear to have discrete evolutionary histories over the last two million years (Bailey et al 2005, Bailey et al 2007a, Bailey et al 2007b).

Populations of large-bodied Mormon crickets generally found west of the Rocky

Mountains often form outbreaks with dense bands that exhibit rapid, cohesive movement over long distances (Cowan 1929; Wakeland 1959; MacVean 1987; Lorch & Gwynne

2000; Gwynne 2001, Lorch et al 2005, Sword et al 2005a, Sword et al 2005b). These outbreak, or BF populations of Mormon crickets are stressed for protein and salt due to an increase in feeding competition with increased population density (Lorch et al. 2005;

Sword et al. 2005a, Simpson et al 2006), and may exhibit reversed sex roles. Under these conditions, females must compete for access to males for the nutrient-rich nuptial gifts that they receive upon mating (Gwynne 1981, Lorch & Gwynne 2000; Gwynne 2001).

The nuptial gift is a spermatophore produced by males of many species of katydid that is transferred to the female during mating, and the nutrients it contains have been shown to influence female fecundity and offspring survival (Bailey & Rentz 1990,

Gwynne 2001). It is presumed to be a limiting factor for females in BF populations when feeding competition is high and the females must compete for males in order to receive 3

this additional nutrition. Males in the BF populations make short, low intensity calls which occur while the “bands” are moving (Gwynne 2001, Bailey et al 2007b, Neal personal observation). The relationship between the call structure and sex role reversal in this population type is currently unknown.

In addition to the outbreak populations, there are populations of smaller-bodied, relatively sedentary NBF Mormon crickets, which are solitary and exhibit typical sex roles. NBF males produce long, relatively more intense calls to compete for mates

(Gwynne 1981, Gwynne 1984; Gwynne 2001; Bailey et al. 2007b). These populations are found in mountain valleys in the eastern part of the species’ range at very low population density. Unlike the dark red or black colored BF Mormon crickets, NBF

Mormon crickets tend to be green or gray in color which allows them to be more cryptic in the lush meadows where they occur.

Figure 1.1 A large bodied BF Mormon cricket male the Eagle Rock site near Elko, NV feeding on another BF Mormon cricket. 4

Figure 1.2 A smaller bodied NBF Mormon cricket male in the Cache la Poudre Canyon, CO with a small radio attached to the pronotum.

Mormon cricket eggs from all types of populations hatch in the spring and nymphs go through seven instars before becoming adults. Reproductive structures do not appear until later in development and wings, which are vestigial in females and only used for calling in males, do not develop until the adult stage. This fairly synchronized emergence and development takes between 60 and 90 days and mating begins approximately two weeks into adulthood. At the time of mating, males transfer nutrient rich spermatophores, or nuptial gifts, to the females. Females oviposit their eggs into the soil where they lie dormant until the spring, however, under some conditions eggs may remain in diapause for up to five years (Gwynne 2001).

Despite high degrees of intraspecific variation in morphology and behavior, BF,

NBF, and intermediate Mormon crickets are currently considered the same species

(Gwynne 2001, Bailey et al 2005, Sword et al 2005, Bailey et al 2007a, Bailey et al 5

2007b). The BF traits such as larger body size, darker coloration, shorter male calls, and cohesive movement over long distances are thought to be plastic and induced by environmental stimuli and population density (Gwynne 2001) although there is some evidence to suggest that BF and NBF Mormon crickets are genetically distinct (Bailey et. al. 2005). Sequencing of the mitochondrial genes COII and COIII from samples of eastern and western Mormon crickets revealed a divergence approximately two million years ago (Bailey et. al. 2005). However, a population of presumed NBF Mormon crickets from a western site called Little Brush Creek grouped more closely with the BF

Mormon crickets in this genetic divergence study. Bailey et al (2005) suggested that the

Mormon crickets in Little Brush Creek may be under unique environmental conditions, and if the gregarious traits are phenotypically plastic, this population may have an unusually high “switch point,” possibly related to food abundance.

Some of the difficulties in analyzing and interpreting Mormon cricket data (e.g.

Lorch & Gwynne 2000, Gwynne 2001, Bailey et al 2005, Lorch et al 2005, Sword et al

2005a, Sword et al 2005b, Bailey et al 2007a, Bailey et al 2007b, Del Castillo & Gwynne

2007) have to do with this high degree of intraspecific variation and the presence of intermediate population types. Since Mormon crickets from the different population types look and behave so dissimilarly, it is nearly impossible to make generalizations about this species. While calling or movement behavior and population density are usually sufficient predictors of population type, a set of morphological criteria may assist in determining the extent of the divergence between BF and NBF Mormon crickets.

Mormon cricket morphology has not previously been described in great detail except for 6

the file and mirror of the wings, head capsule width, and the pronotum, or shield-like covering of the wings (Bailey et al 2007). Furthermore, there have been no previous attempts to describe shape differences in morphology in these or other features between

BF and NBF Mormon crickets, and it is unknown if there are shape differences in morphological features between populations.

TECHNIQUES FOR INVESTIGATING SHAPE DIFFERENCES IN MORPHOLOGY

AND MORPHOLOGICAL INTEGRATION

This thesis aims to systematically describe the morphology in terms of allometric, or size-correlated changes in shape between populations of Mormon crickets, and to examine how the patterns of relationships between morphological characters may have changed over evolutionary time. If the observed patterns of integration are relatively stable between populations, then a likely explanation is that the genetic covariance matrices are also stable (Olson & Miller 1958, Cheverud et al 1985, Cheverud et al 1989,

Gonzalez-Jose et al 2004). If there are patterns of change in morphological integration that relate to differences in function or observed behavioral patterns, then this would be consistent with the alternate hypothesis that there are differences in the organization of covariation in BF and NBF Mormon crickets, rather than the explanation that phenotypic plasticity is a factor of morphological variation. 7

In the 1950s, Everett Olson and Robert Miller developed and introduced morphological integration, the morphometric study of the interrelationships among characters (Olson & Miller 1958). This gave evolutionary biologists a new approach for investigating the mechanisms involved in phenotypic evolution with a focus on the interrelation of parts. Studies of this nature attempt to explain why certain traits covary together strongly while other groups of traits have weaker associations. Differences in the patterns of interrelationships are expected to be the result of changes in the underlying functional and/or developmental properties of phenotypic traits that are under selection.

Advances in methodology in this field have made these techniques very popular and useful for looking at patterns of evolutionary change in organisms ranging from insects to humans (e.g., Blackith 1960, Atchley and Hensleigh 1974, Cheverud 1982, Wagner 1990,

Falsetti et al 1993, Jungers et al 1995, Klingenberg et al 2001, Marroig and Cheverud

2001, Hallgrimsson et al 2002, Gonzales-Jose et al 2004, Marroig et al 2004, Bastir &

Rosas 2005, Monteiro et al 2005, Young and Hallgrimsson 2005, Vinyard 2007, Lawler

2008, Sylvester et al 2008).

MATERIALS AND METHODS

To begin to describe variation between populations of Mormon crickets, I looked for allometric, or shape differences in 23 morphological characters. Morphometrics of head width (HW), head length (HL), maxilla width (MW), pronotum height (PH), 8

pronotum width (PW), pronotum length (PL), femur 1 length (F1L), femur 2 length

(F2L), femur 3 length (F3L), femur 3 width (F3W), tibia 1 length (TI1L), tibia 2 length

(TI2L), tibia 3 length (TI3L), tarsus 1 length (TA1L), tarsus 2 length (TA2L), tarsus 3 length (TA3L), ear length (EL), right wing surface area (RWSA), right wing length

(RWL), right wing width (RWW), mirror length (MIL), mirror width (MIW), and mirror surface area (MISA) were taken from 152 adult Mormon crickets collected from five populations in June-July of 2008.

I estimated body size as the Geometric Mean (GM) of ten characters. The GM, or body size variable contained the volume of each specimen (3√wet weight), and nine other

measurements which captured information about the overall size of Mormon crickets.

Each measured character was divided by the geometric mean which yielded shape ratios

(Mosimann & James 1979). The shape ratios represent a proportional relationship: each character relative to the geometric mean (body size variable) for each individual.

Using this technique, geometric similarity is synonymous with isometry, and allometry refers to non-isometric scaling. In other words, when there are significant

allometric differences, shape changes as a function of size and geometric similarity is not

preserved (Mosimann & James 1979, Jungers et al 1995). The use of Mosiman shape

ratios is an increasingly common way to test allometry, or shape divergences in

characters between populations or species (e.g., Falsetti et al 2003, Vinyard & Hanna

2005, Colgoni & Vamosi 2006, Vinyard 2007, Pizzo et al 2008, Sylvester et al 2008) and

ratios are often preferred over residuals in this type of biological problem because

residuals are “shape-free” and do not allow for size-shape analysis (Jungers et al 1995). 9

Furthermore, the data in this study were not log transformed because log transformations may remove the researcher from the biological relationships in the data, and the use of raw data may be a more powerful way to interpret shape and its covariation with size

(Reyment 1971, Sokal & Rohlf 1981, Corruccini 1987, Hartman 1983, Smith 1984,

Jungers et al 1995).

A preliminary study of Mormon cricket morphology was conducted with these techniques using a morphometric data set of 521 BF and NBF Mormon crickets provided by researchers at the University of Toronto (Chapter II). A study of allometry, or shape differences in form by population type and by sex was also conducted using 152 specimens collected from five populations in 2008 (Chapter III). Principal component analysis of the covariance matrices was employed for data reduction and to explore the interactions between characters among BF and NBF Mormon crickets in terms of variance explained by size and shape versus shape alone (Chapter III). Correlation analysis was employed to test the relationships between morphological characters and movement patterns (Chapter III). With regard to morphological integration, hypotheses of differences in covariation structure, or integration, were tested by constructing correlation matrices of the shape variables and subjecting them to matrix correlations and

Mantel tests. Integration patterns were discussed in terms of shape differences in morphology, local ecological conditions, and selection pressures by population (Chapter

IV).

THE CONTACT CALL HYPOTHESIS FOR COHESIVE MOVEMENT IN MORMON

CRICKETS

Despite evidence that BF Mormon crickets benefit from dilution effects in the form of reduced individual risk of predation (Hamilton 1971; Lorch et al. 2005; Sword et al. 2005), little is known about the mechanisms involved in band formation or cohesion

(Sword 2005). Because of the devastating economic consequences that BF Mormon crickets can cause to agricultural crops and rangeland, there is great interest in understanding the factors that influence band formation so that cost-effective measures can be taken to curb their destruction (Cowan 1929; Wakeland 1959; MacVean 1987).

Mate attraction is presumed to be the function of male calling in katydids, however, contact calling is proposed here as a unique behavior in BF Mormon crickets.

BF Mormon crickets often operate under reversed sex roles which may suggest that BF males have adopted a new function for calling under outbreak conditions when they do not compete to attract mates. Sound may help to explain how some populations of

Mormon crickets form high density bands with cohesive movement as is the case with many social animals such as birds, bats, elephants, and primates (e.g., Digweed 2007,

Carter et al 2008, Kodi et al 2008, Krama et al 2008, Leighty et al 2008).

The contact call hypothesis was tested using techniques for studying morphological integration and modularity (Chapter IV). Modularity is a distinct variational property that is presumed to play a role in how functionally distinct character complexes are integrated (Magwene 2001, Mitteroecker & Bookstein 2007). Certain 11

modules can be seen as a key innovation of a taxon which has allowed for an ability to produce variation in morphological features that can function as adaptations (Yang 2001).

If locomotive and call-producing characters represent a distinct module in BF Mormon crickets, then BF Mormon crickets are expected to have stronger correlations within this module compared to NBF Mormon crickets. A difference in the covariance structure of these characters between population types would be consistent with the hypothesis of the evolution of a character suite for cohesive movement, or a functional change in modularity in BF Mormon crickets (Bolker 2000, Magwene 2001, Yang 2001, Hansen

2003, Mitteroecker & Bookstein 2007). Morphological evidence within this study that would be consistent with the contact call hypothesis should provide encouragement to invest in future behavioral research in the field.

CHAPTER II: A PRELIMINARY STUDY OF MORPHOLOGY IN MORMON

CRICKETS

INTRODUCTION

To assess the utility of using techniques in modularity and integration for examining phenotypic evolution in Mormon crickets, a preliminary study of their morphology was conducted using morphometric data provided by researchers at the University of Toronto

(Kevin Judge personal communication). The primary purpose of this study was to describe

Mormon cricket morphology using the available characters from this data set for adult males and females of band-forming (BF) and non-band-forming (NBF) Mormon crickets.

Specifically, the aim was to compare the degree of sexual size dimorphism by population type and to test for shape differences in the head, maxilla, pronotum, and hind femur by population type, sex, and the effects of population type*sex interactions. Previous efforts to describe head capsule width and pronotum length compared absolute differences between population types and there have not been tests addressing whether or not these characters scale with body size in

Mormon crickets (Bailey et al 2007b).

While this study was mainly exploratory, two hypotheses were tested. First, sexual size dimorphism is absent or reduced in the sex role-reversed BF populations based on the absence of male scramble competition under outbreak conditions. Second, shape differences in pronotum by sex and by population type were also expected due to function. Because the

12 13

pronotum is presumed to act as a speaker cabinet in the amplification of sound (Forrest, 1981,

Gwynne 2001), it was tested whether males would have longer relative pronota than females

and whether NBF males, who call more intensively than BF males, would have longer pronota relative to body size than BF males.

As the forewings of crickets and katydids stridulate, the file (pars stridens) hits the scraper (plectrum), causing the circular membrane (mirror) of the wing to vibrate and produce sound (Forrest 1981). The slightly raised pronotum of these and other shield- backed katydids acts as a resonating chamber, or a speaker cabinet with a closed back and sides. The chamber assists in reducing the geometric spread of the output from the membrane, possibly increasing the efficiency of calling (Forrest 1981). This type of

baffle system prevents the outputs from the two sides of the membrane from interfering

with one another and may also increase the output intensity, or volume (Bailey 1976,

Forrest 1981). The broad hind femurs of some species of crickets have also been seen

positioned during sound production in a way that would extend the area of the cabinet

(Forrest 1981), and it is presumed that a longer cabinet may afford a male more resonating space and increased song efficiency and/or intensity.

METHODS

Five hundred and twenty-one adult Mormon crickets that were collected over several years from eleven different locations were pooled and used in the analyses.

Measurements of head width (HW), maxilla width (MW), pronotum length (APL), and hind femur length (AFL) were taken by students at the University of Toronto to the nearest 0.01 mm using digital images and were provided for these analyses. APL was the average of the left and right sides of the pronotum which were measured independently and AFL was the average of the right and left hind femur lengths. If only one hind femur was measured (for example because of damage to the other hind femur), then the variable was recorded as the length of the one measured femur.

Specimens were identified by their collectors as either “gregarious” or “solitary” based on estimates of population density. The terms BF and NBF are used synonymously with these groupings and these terms have been used here for consistency and because they tend to reflect quantifiable behavioral patterns rather than estimates of population density. Samples from Little Brush Creek, Utah were identified by the collectors as solitary or NBF based on population density, however, in this study of morphology, they grouped more closely with the BF Mormon crickets. They were initially statistical outliers in the NBF data so the analyses were conducted again with the

Little Brush Creek specimens grouped as BF Mormon crickets. This appeared to provide a more accurate depiction of Mormon cricket morphology by population type and was 15

also consistent with findings by Bailey et al (2005) that Little Brush Creek specimens

grouped with gregarious or BF Mormon crickets based on the sequencing of mitochondrial genes COII and COIII.

Figure 2.1 Above is a digital photograph showing how head width (HW) and maxilla width (MW) were measured on the specimens (images for Figures 2.1, 2.2, 2.3 were provided by Kevin Judge).

Figure 2.2 Above is a digital photograph showing how pronotum length (PL) was measured. The right and left sides were measured, and the average pronotum length was the average of the two sides.

Figure 2.3 Above is a digital photograph showing how the left and right hind femurs were measured. The average of the two sides was calculated, and average femur length 17

(AFL) was used for the analyses. If one femur was absent, the femur that was present was used as the AFL.

Raw data were used to compare the absolute size differences in morphology between male and female BF and NBF Mormon crickets rather than log transformed differences. A geometric mean was constructed using the available characters which provided a centroid, or body size variable. The geometric mean was calculated for each

individual using the following equation:

4√(APLxMWxHWxAFL).

The geometric mean was used as an estimate of body size and therefore allowed

us to test differences in the degree of sexual size dimorphism by population type. Shape

ratios were constructed by dividing the value of each character by the geometric mean.

They were plotted and tested for significance of allometric differences with two way

ANOVA (α=0.05) and provided information about shape differences between males and

females and BF and NBF Mormon crickets (See Chapter I for justification of this technique).

A principal components analysis was employed to describe the relationships

between the available characters by population type. Analyses were conducted using

SYSTAT 11.

RESULTS

The geometric mean, or estimated body size variable, was significantly greater for

BF Mormon crickets than for NBF Mormon crickets and was also significantly greater

for females of both forms (Figure 2.4; ANOVA: Population Type: p<0.0001, Sex:

p<0.0001, Interactions: p<0.0001). The difference in geometric mean between males and

females was greater in the NBF Mormon crickets than in the BF Mormon crickets (Figure

1), and the significant interaction effect indicated that there was a significant reduction in

the degree of sexual size dimorphism in BF populations. In other words, BF Mormon

crickets were significantly larger bodied than NBF Mormon crickets, and females of each

population type were significantly larger bodied than males as estimated by the geometric

mean. The presence of a significant interaction effect in this analysis reflected a

difference in the degree of sexual size dimorphism between the population types. There

appeared to be a significant reduction in the degree of sexual size dimorphism in the BF

population type as expected based on the difference in mating patterns.

The BF Mormon crickets had longer absolute pronota than NBF Mormon crickets

and female NBF Mormon crickets had longer absolute pronota than male NBF Mormon

crickets. There was no sexual dimorphism of the pronotum in BF Mormon crickets when

shape differences were not taken into account (Figure 2.5). This was consistent with the

findings by Bailey et al (2005) regarding absolute prontum length. The shape ratio for

the pronotum provided information about the allometric relationship between body size and pronotum, or the length of the pronotum relative to body size. Males of both population types, despite being smaller bodied, had significantly longer pronota relative 19

to body size than females. Additionally, NBF males had significantly longer pronota relative to body size than BF males (Figure 2.6; ANOVA: Population Type: p<0.0001,

Sex: p<0.0001, Interactions: p=0.003). NBF males have been shown to produce longer, more intense calls than BF Mormon crickets (Bailey et al 2007b), and these findings are consistent with the functional hypothesis that a longer relative pronotum aids in sound amplification.

BF Mormon crickets had significantly wider maxillae relative to body size than

NBF Mormon crickets and females had significantly wider relative maxillae than males of both population types (ANOVA: Population Type: p=0.004, Sex: p=0.006,

Interactions: NS). BF Mormon crickets also had significantly wider heads relative to body size than NBF Mormon crickets. As with maxilla width, females of each form had significantly wider heads than males (ANOVA: Population Type: p<0.0001, Sex: p<0.0001, Interactions: NS). BF Mormon crickets had significantly longer hind femurs relative to body size than NBF Mormon crickets. Females of each form had significantly longer relative femurs than males and this difference was more pronounced in the NBF

Mormon crickets (ANOVA: Sex: p=0.000, Population Type: p=0.006, Interactions: NS).

The principal components analysis distinguished the Mormon crickets by population type and by sex with BF females and NBF males the most different on the

PC1 axis, or the axis most commonly associated with size related variation (Figure 2.7).

PC1 explained over 90% of the variance while PC2 explained 5% of the variance in the sample. AFL had the highest loading on PC1 (1.938) and APL had the highest loading on PC 2 (0.507). 20

11 GM 10

8 ♂ 7 ♀ BF NBF

Population Type

Figure 2.4 A box plot of Geometric Mean (GM) by Population Type shows that Band- forming (BF) Mormon crickets were significantly larger bodied than Non-band-forming (NBF) Mormon crickets and females were significantly larger bodied than males in both groups although to a lesser degree in BF populations (ANOVA: Sex: p<0.0001, Population Type: p<0.0001, Interaction: p<0.0001). The center bars represent the medians, the boxes contain 50% of the data, the lines beyond the boxes show 95% of the data, and the stars and circles represent statistical outliers in the data.

APL 13 12

9 ♂ 8 ♀ BF NBF Population Type

Figure 2.5 A plot of Average Pronotum Length (APL) by Population Type shows that BF Mormon crickets had longer absolute pronota than NBF Mormon crickets. NBF females had longer absolute pronota than males and the pronotum was not sexually dimorphic in BF Mormon crickets.

1.3

APL 1.2 SHAPE

1.1

1.0

♂ 0.9 ♀ BF NBF Population Type

Figure 2.6 The plot of Average Prontum Length Shape (APL SHAPE) by Population Type shows that when the pronotum length is compared to the geometric mean, or body size variable, males have significantly longer relative pronota than females in both population types. Additionally, NBF males, despite being the smallest bodied, had the longest relative pronota (ANOVA: Sex: p<0.0001, Population Type: p<0.0001, Interactions: p=0.003).

PC2

N BFM -1 N BFF B FM

-2 BFF -10 -5 0 5 PC1

Figure 2.7 The principal components analysis of the covariance matrices of HW, MW, APL, and AFL for Mormon crickets shows that smallest individuals, NBF males (NBFM) are the most easily distinguished from the largest individuals, BF females (BFF) on PC1. NBF females (NBFF) with the smallest pronota are the most easily distinguished from BF males who have the largest pronota (BFM) on PC2. Relative size is not taken into consideration in this analysis. The per cent of variance explained by PC1 was 90.749%, PC2: 5.411%, n=521.

APL MW HW AFL 24

APL 0.982 MW 0.493 0.512 HW 0.626 0.468 0.591 AFL 1.528 1.133 1.373 3.833

Table 2.1 Matrix to be factored

1 2 3 4 5.371 0.320 0.171 0.056

Table 2.2 Eigenvalues 1 2 3 4

90.749 5.411 2.896 0.943

Table 2.3 Per cent of total variance explained by components

1 2 3 4

AFL 0.836 -0.433 -0.303 0.145 APL 0.365 0.896 -0.194 0.163 HW 0.314 0.099 0.293 -0.898 MW 0.262 0.015 0.886 0.383

Table 2.4 Eigenvectors

1 2 3 4

AFL 1.938 -0.245 -0.125 0.034 APL 0.847 0.507 -0.080 0.039 HW 0.727 0.056 0.121 -0.212 MW 0.608 0.009 0.367 0.090

Table 2.5 Component Loadings

DISCUSSION 25

All four available characters showed significant shape differences between male and female BF and NBF Mormon crickets. Since calling and movement behavior also differ greatly between population types, these shape differences may have implications for differences in functional morphology in these and other allometrically differing characters. For example, the pronotum was expected to be longer relative to body size in

NBF males where the calls have been observed to be relatively more intense in volume than in the BF males (Bailey et al 2007b). The results were consistent with the functional hypothesis that a longer pronotum aids in sound amplification. Since movement patterns and call structure vary highly between population types, it was expected that there would be shape differences in locomotive morphology and call-producing characters between

BF and NBF Mormon crickets.

This study also tested the degree of sexual size dimorphism in Mormon crickets using the GM as an estimate of body size. It was previously reported that only BF

Mormon crickets exhibit sexual size dimorphism (Gwynne 1981, Gwynne 1984), and then Bailey et al (2007b) found that only NBF Mormon crickets are sexually dimorphic.

Both studies used the pronotum as a measure of body size, which appears to be an unreliable predictor of body size in Mormon crickets since there are significant shape differences in the pronotum by sex and by population type.

BF and NBF Mormon crickets were both significantly sexually dimorphic in geometric mean, however, as indicated by the significant interaction effect, the degree of size dimorphism was greater in NBF Mormon crickets with females being larger than males. This may reflect the reversal of sex roles typical in BF populations and a longer 26

development time for males at each instar in these populations (Gwynne 2001). One hypothesis for the tendency for females to be larger than males in ectotherms deals with a differential in timing of development between males and females. This is presumed to be related to male scramble competition for mates. With the early arrival of adult males to prime breeding locations, males are prepared to mate when females reach sexual maturity, although there is a negative trade-off between development time and growth

(Andersson 1994). In other words, by speeding up development in order to be ready to mate when females are ready to mate, males compromise body size due to a shorter period of development for growth at each instar. As a result, males tend to be smaller bodied than females. In the NBF population type, this may explain the difference in sexual size dimorphism, and it may also explain why male and female BF Mormon crickets are similarly sized when sex roles are reversed.

Another possible explanation for this pattern would be a simple inversion of

Rensch’s rule, as is seen in other orthopterans such as Dichroplus pratensis (Bidau &

Marti 2007). Rensch’s rule states that in many sexually dimorphic vertebrates, the degree of sexual size dimorphism increases with body size , however, this tendency may be reversed in some cases (Rensch 1959, Anderson 1994). It may be the case here, as in other ectotherms where females are larger than males that as body size increases, the degree of sexual size dimorphism decreases. Mormon crickets appear to fit this pattern with the larger body-sized BF type exhibiting reduced to no sexual size dimorphism.

Through the examination of these four available characters, encouragement was provided to select several other morphological characters for comparisons of shape 27

differences between BF and NBF Mormon crickets. Only four characters were available

for this study which placed constraints on the selection of a geometric mean. Ideally a

geometric mean would be tailored to capture size information relevant to a particular question, rather than constructed using only the available characters.

Because BF and NBF Mormon crickets differ so greatly in calling and movement behavior, a great deal of insight could be gained by looking at shape differences in the functional morphology of call-producing and locomotive characters. If possible such a study would include a field component and the comparison of behavioral data to morphometrics so that the functional implications for shape differences could be better understood. Shape differences in head width and maxilla width by population type may also reflect dietary differences which can be quantified using stable isotope data. Since differences in shape have been identified between the sexes and between groups, this may also indicate the presence of differences in the structure of the covariance matrices between BF and NBF Mormon crickets, which may have implications for the extent and nature of divergence between population types.

CHAPTER III: SHAPE DIFFERENCES IN MORPHOLOGY IN MORMON

CRICKETS

INTRODUCTION

Analyses of the relationships between size and shape or organismal scaling

studies contribute significantly to descriptions of morphological variation and

explanations of phenotypic evolution (Gould 1966, Mosimann & James 1979, Cheverud

1982, Smith 1984, Reist 1985, Corruccini 1987, Cheverud et al 1989, Falsetti et al 1993,

Jungers et al 1995, Smith 2005). Since shape may or may not be correlated with size and

because shape differences may be related to functional differences in morphology,

geometric similarity is best not assumed when there are differences in overall body size

between organisms (Gould 1966, Corruccini 1973, Falsetti et al 1992, Jungers et al

1995). Mormon crickets provide an interesting system for investigating functional shape

differences because of the tremendous overall body size difference between BF and NBF

population types and the broad range of intraspecific variation found in several other characteristics such as calling and movement behavior.

Larger bodied BF Mormon crickets occur at high population densities and migrate

over long distances in cohesive groups while NBF Mormon crickets are smaller bodied,

solitary, and relatively sedentary. Male BF Mormon crickets also produce relatively

shorter and less intense calls than NBF Mormon crickets (Gwynne 2001, Bailey et al

28 29

2007b, Neal personal observation). There is some evidence to suggest that intermediate

morphotypes also occur although little is known about these populations or what factors

influence these intermediate morphologies. Little Brush Creek, UT, has been identified as a solitary or NBF population based on density , however, morphologically (Chapter

II), geographically, and genetically they grouped with the BF population type, or the western clade (Bailey et al 2007a, 2007b). In July 2008, two populations of Mormon crickets were observed at sites less than six kilometers apart in eastern Utah which appeared to be an intermediate morphotype (Neal personal observation, Lorch personal communication).

We expected multiple shape differences in morphology between the population types that would relate to differences in movement and calling behavior. This chapter contains descriptions and discussion of the morphology of BF, NBF, and intermediate population types of Mormon crickets in terms of shape differences relative to body size.

Movement behavior by population type has also been described as a way to investigate the relationship between shape differences in morphology and the rate of movement by population type.

Previous studies of morphology in Mormon crickets have failed to investigate size-correlated changes in shape between population types (Bailey et al 2007b), however, the preliminary analyses in Chapter II have shown that not only do BF and NBF Mormon crickets differ dramatically in body size, but there are at least four continuous characters in which there are significant shape differences between BF and NBF male and female

Mormon crickets. For example, despite being the smallest bodied of the four class types, 30

NBF males had the longest relative pronota, which may be related to the function of the pronota in sound amplification. This preliminary study provided encouragement to seek out additional characters that may exhibit shape differences that could be related to functional or behavioral differences between the population types.

STUDY QUESTIONS

Two main questions related to shape differences were addressed in this exploratory study of morphology between the different population types of Mormon crickets. 1. Are BF and NBF Mormon crickets similar in character shapes despite overall body size differences? 2. Is the intermediate population type more similar in character shapes to a population type of similar overall size? The shape differences were expected to reflect differences in behavioral abilities, and hypotheses for shape differences by sex and by population type were based on assumptions about the functional roles of the various character shapes (Table 3.1).

Principal component analysis was employed to investigate whether size and shape

(based on raw size measurements) or shape alone (based on shape ratios calculated as the ratio of a size measurement divided by the geometric mean of ten variables) contained more of the overall variance between population types. While size-related variation was expected to account for a great deal of the variance between population types, shape- related variation was also expected to be significant between population types. 31

Movement data was also collected via radio telemetry and used to investigate the relationships between morphology and movement in Mormon crickets. Relationships between the character shapes and movement data were investigated using correlation analysis. It was expected that locomotive features would be positively correlated with rate of movement, and that other features such as measures of the head, wings, and pronotum would not be correlated with rate of movement. The front and middle femur shapes were expected to have the strongest relationship with rate of movement, and the hind limb was expected to be most heavily involved in jumping behavior, rather than rapid walking.

Pop. Sex Assumed Functional Roles of Characters Type Head Width Shape BF F Head shapes were expected to be largest in BFF due to Head Length Shape presumed dietary differences. BFF are the largest and Maxilla Width Shape possibly most highly cannibalistic group, requiring relatively larger heads and mandibles for eating conspecifics (conspecifics are likely the largest prey item in the Mormon cricket diet). Pronotum Width Shape - - No significant shape differences were expected. The pronotum width was expected to reflect a measure of body width rather than a functional characteristic. Pronotum Height Shape NBF M Pronotum height and length were expected to be relatively Pronotum Length Shape largest in NBF males, who have been found to call the most loudly. The pronotum is presumed to act as a speaker box, increasing the efficiency and intensity of the calls. Ear Length Shape NBF F NBF Mormon crickets are relatively dispersed, and the females were expected to have larger relative ears for locating calling males. Femur 1 Length Shape BF - Extended, or larger relative front and middle femurs and Femur 2 Length Shape tibias may raise the front of the body and allow for more Tibia 1 Length Shape even walking. In the BF population type, this may Tibia 2 Length Shape influence rate of movement and they were expected to have larger relative front and middle femurs. Femur 3 Length Shape NBF - This limb was expected to be relatively reduced in the BF Femur 3 Width Shape type, which may exhibit morphology that is more efficient Tibia 3 Length Shape for walking. The hind limb is presumed to be most Tarsus 3 Length Shape important for the catapult system of jumping, which is expected to be less important than efficient or rapid walking in the BF type. Tarsus 1 Length Shape BF - Longer relative tarsi were expected for the BF type in order Tarsus 2 Length Shape to increase surface area on the ground for more efficient or rapid walking. Right Wing Width Shape NBF M NBF males were expected to have relatively larger wing Right Wing Length features than BF males due to the known differences in call Shape intensity, or volume between the population types. Wing Mirror Width Shape size and mirror size are presumed to have a positive Mirror Length Shape relationship with Carrier frequency and call intensity Right Wing Shape (Bailey et al 2007 b). Mirror Shape

Table 3.1 The hypotheses and basis for the predictions for shape differences by population type and sex are presented above.

METHODS

Mormon crickets from four populations in the western United States were tracked using radio telemetry and were then collected for morphological measurements. Six NBF

Mormon crickets were tracked for 18 hours at Kelly Flats (KF) and Indian Meadows (IM) in the Cache la Poudre Canyon, CO. Six intermediate Mormon crickets were tracked for five hours at Diamond Mountain (DM) near Vernal, UT. Forty-three BF Mormon crickets were tracked for 20 hours at Eagle Rock (ER) near Elko, NV. This movement data can provide information about distance traveled, rate of movement, and direction of movement, which all aid in understanding how cohesive bands move compared to solitary individuals (Lorch & Gwynne (2000) or Lorch et al (2005)).

I measured 23 morphological characters (see Chapter 1) from 152 adult Mormon cricket specimens collected from five different populations in June-July 2008. One population of BF Mormon crickets was sampled at ER (99 individuals). Two populations of NBF Mormon crickets were sampled from IM (seven individuals) and KF (19 individuals). Two populations of intermediate Mormon crickets were sampled from

Upper Rye (UR) (eight individuals) and DM (19 individuals). The specimens were placed in individual plastic baggies, frozen with dry ice, and shipped from Salt Lake City,

Utah to Kent State University in Kent, OH where they were kept frozen until 30 minutes before measurement. 34

All specimens were weighed to the nearest 0.0001 g and the wet weight was

converted to volume. Measurements of all non-eletryl characters were taken using fine

pointed digital calipers to the nearest 0.01 mm with automatic entry into an Excel

spreadsheet. The wings were removed from the bodies of 76 males using scissors and

dried in an oven at 40º C for 48 hours. The wings were weighed to the nearest 0.0001 g

and then digital photographs were taken under a microscope using the ProgRes Mac

Capture Pro 2.5 software. The ImageJ digital measuring program was employed to

calibrate the images and to measure right wing lengths, widths, mirror lengths and

widths, and right wing and mirror surface areas as the distance between points or

landmarks on the images.

I estimated body size as the geometric mean of ten variables which were intended

to capture as much information as possible about overall body size including volume,

three head size variables, three pronotum size variables, and three leg size variables. The

geometric mean was calculated for each individual using the following equation:

10√ [HWxHLxMWxPLxPHxPWxF1LxF2LxF3Lx(3√WW)].

Shape ratios were calculated for each character by dividing the value of the

character by the geometric mean for each individual. Shape ratios for the right wing and

mirror were calculated by taking the square root of the surface area of the right wing

divided by the geometric mean and by taking the square root of the mirror surface area

divided by the geometric mean respectively. A priori hypotheses about which population were expected to have a larger shape ratio are indicated in Table 3.1 above and in table

3.12 by an H in the appropriate column for a population. The geometric mean and all 35

shape ratios were tested for population, sex, and interaction effects with two way

ANOVA (α=0.05) using SYSTAT 11 (for justification of these methods see Chapter 1).

Figure 3.1 Using the digital calipers, head width, the distance measured from the outsides of each of the eyes, is being measured and recorded.

Figure 3.2 The landmarks where head length and maxilla width were taken from are shown above. Head length was measured from the top of the head between the antennae to the point where the mandibles join. Maxilla width was taken from the outside of each mandible. 36

Figure 3.3 Using the digital calipers, tarsus 2 length (TA2L) is being measured and recorded. Tarsi 1 and 3 were measured in the same way.

Figure 3.4 The landmarks for measuring the hind femur (F3L), tibia (TI3L), and tarsus (TA3L) lengths are shown above. They were measured using digital calipers.

Figure 3.5 The landmarks for measuring pronotum width (PW), and the front and middle tibias (F1L, F2L, TI1L, TI2L) are shown above.

Figure 3.6 The landmarks for measuring ear length (EL), Pronotum height (PH), and pronotum length (PL) are shown above.

Figure 3.7 Right wing length (RWL) and right wing width (RWW) were measured by calculating the distances between points using the ImageJ program. The landmarks used are shown above.

Figure 3.8 The landmarks for mirror length (MIL), shown as a vertical line, and mirror width (MIW), shown as the horizontal line, are shown above.

RESULTS: PRINCIPAL COMPONENT ANALYSIS

The comparison of the principal component analysis of size and shape (raw variables) with the principal component analysis of shape alone (shape ratios) was used to determine the extent to which the overall differences between population types could be attributed to size and shape versus shape alone (e.g. Falsetti et al 1992). In other words, these analyses were employed to address the question of whether the variance explained by size and shape exceeded the variance explained by shape alone between the three population types of Mormon crickets. The principal component analysis of the size and shape matrix included size related variation while the analysis of the shape matrix represented aspects of morphological variation that were unrelated to size.

The first principal component of the size and shape analysis accounted for over

92% of the total variance in the sample (n=152). This component typically reflects variation in size plus size-related shape. All of the eigenvector coefficients for this component were positive, and TI3L had the highest loading (0.5446). The second principal component of this analysis accounted for just over 1% of the total variance and this component represented aspects of morphological variation that were not related to size. F1L, F2L, TI1L, TI2L, TI3L, and TA2L, or in other words almost all of the locomotive features, had negative loadings on this axis while PL had the highest positive loading (0.6748). Males and females of all three population types were clearly distinguishable on PC1 with NBF males the smallest and most different on this axis from 40

BF females (Figure 3.8). As expected, intermediate males and females grouped between

BF and NBF specimens (Figure 3.8).

The results for the shape analysis indicated that there was a major reduction in

the amount of variance explained when geometric size was excluded from the PCA.

Principal component 1 of the shape analysis accounted for just 54% of the total variance in the sample. Locomotive characters featured the positive loadings on PC1 with TI3LS the highest (0.5658) while non-locomotive characters such as the shapes of the head, pronota, and ears, featured negative loadings. For PC2, which accounted for 11.5% of the variance in the sample, F3LS had the highest loading (0.6167) followed by TI3LS

(0.4730). F1LS, F2LS, TI1LS, TI2LS, TA2LS, and PWS had negative loadings on this axis. Males and females of all three population types were also easily distinguishable

with this analysis, and PC2 was relatively more useful for distinguishing populations and

sexes when only shape data are used in the PCA (Figure 3.9).

PC2 0

-1 NBFM NBFF -2 BFM BFF IM -3 IF -20 -10 0 10 PC1

Figure 3.9 The PCA of size and shape by sex and population type (IF: Intermediate females, IM: Intermediate males, BFF: BF females, BFM: BF males, NBFF: NBF females, NBFM: NBF males). PC1 represents variation in size related shape and PL has the highest loading on PC2. Relative size is not accounted for in this analysis. BF females are the most different from NBF males on PC1, or the component that represents size related variation.

PW TA1L TA2L TA3L HW

PW 1.059278 TA1L 0.698105 0.599167 TA2L 0.767166 0.623941 0.724893 TA3L 0.925067 0.709278 0.775334 1.106808 HW 0.554398 0.393361 0.429992 0.515840 0.336234 MW 0.674385 0.476761 0.520632 0.642947 0.386249 HL 1.031446 0.753432 0.818001 0.984006 0.602678 PH 0.557286 0.389513 0.419611 0.547562 0.315304 PL 1.254324 0.907630 0.968685 1.161271 0.688749 F3W 0.519412 0.377486 0.408060 0.496560 0.294743 F1L 1.064974 0.818643 0.888388 1.044523 0.603182 F2L 1.339316 1.004249 1.097419 1.291233 0.747494 F3L 2.389119 1.812744 1.949306 2.316753 1.377584 TI1L 1.467143 1.119483 1.218252 1.392632 0.812827 TI2L 1.768977 1.328755 1.450080 1.705338 0.980354 TI3L 2.903272 2.199122 2.366261 2.849350 1.652447 EL 0.106843 0.055413 0.070397 0.093471 0.058181

MW HL PH PL F3W

MW 0.490950 HL 0.721094 1.171883 PH 0.378966 0.610138 0.550326 PL 0.823311 1.293467 0.734714 1.880054 F3W 0.354284 0.555557 0.316229 0.682810 0.310032 F1L 0.737063 1.167880 0.624920 1.386389 0.580608 F2L 0.905429 1.439348 0.773305 1.718427 0.725321 F3L 1.653913 2.635820 1.381854 3.130880 1.325254 TI1L 0.996126 1.586197 0.815956 1.864001 0.782115 TI2L 1.199378 1.901145 0.988986 2.243037 0.944443 TI3L 2.021640 3.168498 1.670520 3.740283 1.572040 EL 0.067890 0.101662 0.078773 0.094008 0.048925

F1L F2L F3L TI1L TI2L

F1L 1.330963 F2L 1.592117 2.051563 F3L 2.806078 3.481798 6.591831 TI1L 1.745813 2.136188 3.813950 2.504483 TI2L 2.087213 2.629331 4.569487 2.860754 3.589888 TI3L 3.387207 4.174809 7.662592 4.655406 5.592379 EL 0.085355 0.101879 0.225257 0.128690 0.140225 43

TI3L EL

TI3L 9.596751 EL 0.242051 0.138430

Table 3.2 Matrix to be factored

1 2 3 4 5

31.575016 0.444895 0.371444 0.316949 0.268639

Table 3.3 Eigenvalues

1 2 3 4

TI3L 0.544635 -0.301890 -0.518876 0.349942 F3L 0.448761 0.098653 -0.397032 -0.566317 TI2L 0.328028 -0.301196 0.485494 -0.055716 TI1L 0.272469 -0.246641 0.265670 -0.102541 F2L 0.247266 -0.061933 0.362117 -0.150769 PL 0.221940 0.674764 0.116293 -0.213282 F1L 0.199448 -0.053900 0.200443 -0.069196 HL 0.185835 0.111197 -0.018981 0.064119 PW 0.171615 0.240435 0.160473 0.145488 TA3L 0.166887 0.160404 0.091555 0.575041 TA2L 0.139766 -0.004720 0.188451 0.134681 TA1L 0.129109 0.011044 0.096074 0.082600 MW 0.117808 0.088610 -0.021319 0.142475 PH 0.098976 0.373854 0.014946 0.242651 HW 0.096941 0.112373 -0.032708 0.047189 F3W 0.092879 0.142551 0.004814 -0.009258 EL 0.015042 0.094434 -0.031764 0.088293

Table 3.4 Eigenvectors 1 2 3 4

TI3L 3.060396 -0.201362 -0.316235 0.197011 F3L 2.521663 0.065802 -0.241976 -0.318826 TI2L 1.843241 -0.200899 0.295890 -0.031367 TI1L 1.531048 -0.164510 0.161916 -0.057729 F2L 1.389428 -0.041310 0.220697 -0.084880 PL 1.247119 0.450070 0.070876 -0.120074 F1L 1.120730 -0.035952 0.122163 -0.038956 44

HL 1.044240 0.074169 -0.011568 0.036098 PW 0.964335 0.160371 0.097802 0.081907 TA3L 0.937764 0.106990 0.055799 0.323738 TA2L 0.785366 -0.003148 0.114854 0.075823 TA1L 0.725487 0.007367 0.058554 0.046502 MW 0.661985 0.059104 -0.012993 0.080211 PH 0.556164 0.249362 0.009109 0.136608 HW 0.544726 0.074953 -0.019934 0.026566 F3W 0.521905 0.095082 0.002934 -0.005212 EL 0.084521 0.062988 -0.019359 0.049707

Table 3.5 Component Loadings

1 2 3 4

92.776181 1.307225 1.091406 0.931285

Table 3.6 Per cent of total variance explained by components

0.4

0.3

0.2

PC2 0.1

0.0 NBFM -0.1 NBFF BFM -0.2 BFF IM -0.3 IF -1.0 -0.5 0.0 0.5 PC1

Figure 3.10 The PCA of shape by sex and population type. Locomotive characters have the highest loadings on PC1 with TI3LS the highest (0.5658). F3LS had the highest loading on PC2 (0.6167).

PWS TA1LS TA2LS TA3LS HWS

PWS 0.001298 TA1LS -0.000007 0.001703 TA2LS 0.000036 0.001424 0.002288 TA3LS 0.000009 0.000881 0.000994 0.003486 HWS 0.000205 -0.000249 -0.000310 -0.000238 0.001140 MWS 0.000181 0.000026 0.000047 0.000193 0.000282 HLS -0.000000 -0.000062 -0.000176 -0.000145 0.000994 PHS -0.000468 -0.000706 -0.000882 -0.000297 0.000289 PLS -0.000050 -0.000086 -0.000517 -0.000392 0.000170 F3WS -0.000039 0.000114 0.000092 0.000102 -0.000060 F1LS -0.000573 0.001007 0.001200 0.000551 -0.001095 F2LS -0.000505 0.001075 0.001359 0.000515 -0.001504 F3LS -0.000778 0.001293 0.001071 0.000410 -0.000208 TI1LS -0.000308 0.001892 0.002245 0.000713 -0.001926 TI2LS -0.000419 0.001908 0.002420 0.001144 -0.002376 TI3LS -0.000583 0.002416 0.002449 0.001795 -0.001589 ELS 0.000262 -0.000461 -0.000411 -0.000174 0.000694

MWS HLS PHS PLS F3WS

MWS 0.000599 HLS 0.000279 0.001777 PHS -0.000355 0.000254 0.003347 PLS -0.000438 -0.000205 0.000062 0.004401 F3WS -0.000020 -0.000070 -0.000040 0.000136 0.000475 F1LS -0.000191 -0.000814 -0.001360 -0.000861 0.000072 F2LS -0.000425 -0.001379 -0.001814 -0.001234 0.000148 F3LS -0.000060 0.000421 -0.001785 -0.000246 0.000419 TI1LS -0.000188 -0.001345 -0.002599 -0.001487 0.000199 TI2LS -0.000301 -0.001911 -0.003082 -0.001952 0.000239 TI3LS 0.000281 -0.000837 -0.003057 -0.001412 0.000372 ELS 0.000138 0.000642 0.000836 -0.000119 -0.000082

F1LS F2LS F3LS TI1LS TI2LS

F1LS 0.003026 F2LS 0.002865 0.004778 F3LS 0.001781 0.002084 0.008260 TI1LS 0.004051 0.004718 0.003439 0.009104 TI2LS 0.004640 0.006489 0.003423 0.008586 0.012402 TI3LS 0.004241 0.004820 0.006768 0.008614 0.009820 ELS -0.001172 -0.001618 -0.000428 -0.001823 -0.002423 47

TI3LS ELS

TI3LS 0.017349 ELS -0.002192 0.002491

Table 3.7 Matrix to be factored

1 2 3 4 5

0.042109 0.008965 0.004745 0.004401 0.003793

Table 3.8 Eigenvalues

1 2 3 4

PLS -0.080693 0.136511 -0.567800 -0.688899 F3LS 0.251922 0.616701 -0.445575 0.468185 TI3LS 0.565764 0.473027 0.382172 -0.410864 ELS -0.109110 0.125640 0.138582 0.213333 HLS -0.065279 0.219105 0.111798 0.186728 F2LS 0.270854 -0.273622 -0.178153 0.141537 TA3LS 0.066699 0.032223 0.404854 -0.113195 HWS -0.093724 0.165327 0.069552 0.081254 F1LS 0.215862 -0.140705 -0.076302 0.067782 TI1LS 0.412575 -0.192919 -0.078865 0.057474 TA2LS 0.122407 -0.030897 0.109063 0.051281 TI2LS 0.489788 -0.382170 -0.072405 0.050969 PWS -0.026663 -0.032804 0.097538 -0.048850 MWS -0.004620 0.054130 0.148189 0.037053 TA1LS 0.107483 0.037425 0.041845 -0.017386 PHS -0.151590 0.004187 0.192005 -0.016677 F3WS 0.014807 0.028447 -0.039430 -0.010985

Table 3.9 Eigenvectors

1 2 3 4

PLS -0.016559 0.012926 -0.039113 -0.045702 F3LS 0.051695 0.058393 -0.030694 0.031060 TI3LS 0.116097 0.044789 0.026326 -0.027257 ELS -0.022390 0.011896 0.009546 0.014153 48

HLS -0.013396 0.020746 0.007701 0.012388 F2LS 0.055580 -0.025908 -0.012272 0.009390 TA3LS 0.013687 0.003051 0.027889 -0.007509 HWS -0.019232 0.015654 0.004791 0.005390 F1LS 0.044296 -0.013323 -0.005256 0.004497 TI1LS 0.084662 -0.018267 -0.005433 0.003813 TA2LS 0.025118 -0.002926 0.007513 0.003402 TI2LS 0.100506 -0.036186 -0.004988 0.003381 PWS -0.005471 -0.003106 0.006719 -0.003241 MWS -0.000948 0.005125 0.010208 0.002458 TA1LS 0.022056 0.003544 0.002883 -0.001153 PHS -0.031107 0.000396 0.013226 -0.001106 F3WS 0.003038 0.002694 -0.002716 -0.000729

Table 3.10 Component Loadings

1 2 3 4

54.037167 11.505241 6.089468 5.647868

Table 3.11 Per cent of total variance explained by components

RESULTS: SHAPE DIFFERENCES BETWEEN BF AND NBF MORMON CRICKETS

The mean BF population wet weight was greater than 2 times the mean wet weight of the NBF populations. BF Mormon crickets were also found to be significantly larger bodied than NBF Mormon crickets and females in both populations were significantly larger than males as estimated by the geometric mean (Figure 3.10). All but four out of the 23 measured characters were found to be significantly different in shape between BF and NBF Mormon crickets (Table 3.12). The character shapes that tended to be preserved with body size differences by population type (NS in Table 3.12), or in 49

other words featured non-significant shape differences with size, were maxilla width

shape (MWS), pronotum width shape (PWS), femur 3 length shape (F3LS), and femur 3

width shape (F3WS).

The results for pronotum length shape (PLS) were consistent with the findings for

PLS in the preliminary study of morphology in Mormon crickets (Chapter II) with males having significantly longer pronota than females, and NBF males having the longest relative pronota of all four groups (Figure 3.11). While F3L shape and F3W shape did not differ significantly in shape with size differences by population type, F3L shape was significantly greater in females than in males of both population types. The length shapes of the front and middle femurs (F1LS and F2LS) increased with body size, or in other words featured positive shape differences in the BF population type and in females of both population types. The first, second, and third tibias (TI1LS, TI2LS, and TI3LS) were also relatively larger in BF Mormon crickets and in females of both population types. Despite being smaller bodied, NBF Mormon crickets appeared to have significantly increased relative head width and head length shape compared to BF

Mormon crickets, with females of both types having relatively longer and wider head shapes than males (Table 3.12).

NBF Mormon cricket males, despite being smaller bodied also had significantly increased wing and mirror shapes in all measured dimensions including right wing length shape (RWLS), right wing width shape (RWWS), right wing shape (RWS), mirror length shape (MILS), mirror width shape (MIWS), and mirror shape (MIS) compared to BF 50

males (Table 3.12). These results were consistent with findings that NBF Mormon

crickets call longer and more loudly than BF Mormon crickets (Bailey et al 2007b).

Ear length shape (ELS) featured an interesting interaction effect that showed a

reverse in sexual size dimorphism between the population types. Female NBF Mormon

crickets had significantly longer ears relative to body size than NBF males , however, BF

males had significantly longer relative ears than BF females. ELS in NBF Mormon

crickets was overall greater than ELS in BF Mormon crickets (Figure 3.12).

GM 8

♂ 6 ♀ NBF BF

Figure 3.11 A plot of the Geometric Mean (GM) in mm by population type and by sex shows that BF Mormon crickets are significantly larger bodied than NBF Mormon crickets, and females of both population types are significantly larger than males (ANOVA: Population Type: p<0.0001, Sex: p<0.0001 Population Type*Sex: NS p=0.809).

1.9

1.8

1.7 PLS 1.6

1.5

1.4 ♂ 1.3 ♀ NBF BF

Figure 3.12 A plot of Pronotum Length Shape by population type and by sex shows that NBF Mormon crickets had significantly longer relative pronota and that males had significantly longer pronota than females (ANOVA: Population Type: p=0.012 Sex: p<0.0001 Population type*Sex: NS p=0.054).

0.5

0.4 ELS

0.3

♂ 0.2 ♀ NBF BF

Figure 3.13 A plot of Ear Length Shape (ELS) by population type and by sex shows that female NBF Mormon crickets had longer ears than male NBF Mormon crickets , however, there was reverse sexual size dimorphism in ear length in the BF population type (ANOVA: Population Type: p<0.0001, Sex: NS p=0.553, Population type*Sex: p=0.003).

NBF BF NS Sex ANOVA results: PT Sex PT*Sex Head Width Shape O H F *** * NS Head Length Shape O H F *** * NS Maxilla Width Shape H O NS NS NS Pronotum Width Shape HO NS NS NS Pronotum Height Shape HO *** NS NS Pronotum Length Shape HO M * *** NS Ear Length Shape HO O NBFF *** NS ** BFM Femur 1 Length Shape HO F *** ** NS Femur 2 Length Shape HO F *** *** NS Femur 3 Length Shape H O F NS *** NS Femur 3 Width Shape H O NS NS NS Tibia 1 Length Shape HO F *** *** NS Tibia 2 Length Shape HO F *** *** NS Tibia 3 Length Shape H O F *** *** NS Tarsus 1 Length Shape HO *** NS * Tarsus 2 Length Shape HO *** NS * Tarsus 3 Length Shape H O * NS NS Right Wing Width Shape HO *** Right Wing Length Shape HO *** Mirror Width Shape HO *** Mirror Length Shape HO *** Right Wing Shape HO *** Mirror Shape HO ***

Table 3.12: The hypotheses (H) and the observed results (O) for larger shape ratios in the 23 characters that were measured in BF and NBF Mormon crickets are presented above. When H and O appear together in one column and that trait had a significant effect in the ANOVA, the hypothesis was supported. The hypothesized and observed non-significant (NS) shape differences, or “isometric” characters are indicated in a separate column, e.g. maxilla width shape (MWS), pronotum width shape (PWS), femur 3 length (F3LS), and femur 3 width shape (F3WS). Where there were significant differences in shape by sex, the observed increased shape differences are indicated with the corresponding sex (M or F). The ANOVA significance levels for population type, sex, and population type*sex interaction effects are also provided (* = 0.05, ** = 0.01, *** < 0.01).

RESULTS: SHAPE DIFFERENCES BETWEEN THREE POPULATION TYPES

Twenty-seven individuals were collected at two sites in eastern Utah less than six km apart and morphometrics were taken for comparison to BF and NBF morphometrics.

Shape ratios of 21 characters for the specimens collected at these two sites were observed to be significantly different than either BF or NBF specimens (Table 3.13).

Population density of Mormon crickets in eastern Utah was qualitatively estimated to be intermediate between the BF and NBF populations that were observed in the same season. Six individuals at DM were tracked using radio telemetry for approximately five hours, and they more closely resembled the NBF population type in movement behavior. Further, male calling behavior was qualitatively observed to more closely resemble typical NBF calling behavior (Neal personal observation, Lorch personal communication). For example, males at DM were observed calling relatively longer than typical BF males while remaining relatively sedentary. This was consistent with the findings by Bailey et al (2007b) that NBF males produce calls that are longer and more intense than BF males. The coloration of individuals in this population was dark green to gray. UR individuals were found less than six kilometers from DM and no estimates were made on their movement or calling behavior due to time constraints. 55

Coloration of the UR individuals was observed to be dark red to black, a color more

typical of BF populations.

As estimated by the geometric mean, the intermediate population type was

intermediate in body size to the BF and NBF population types with females significantly larger than males (Figure 3.13). They were also intermediate in Femur 1 length shape

(Figure 3.14), all of the wing features including right wing shape (Figure 3.15), and mirror shape (Figure 3.16). Intermediate males had intermediate pronotum shapes, ear shapes, and hind femur width shapes while intermediate females had intermediate femur

2 and tibia 1 and 2 shapes (Table 3.13).

9 GM

♂ 6 ♀ NBF BF I

Figure 3.14 A plot of Geometric Mean (GM) by population type and by sex shows that the BF population type was the largest followed by the intermediate population type (I) and the NBF population type was the smallest. Females in each population type were 56

larger than males (ANOVA: Population Type: p<0.0001, Sex: p<0.0001, Population Type*Sex: NS p=0.759).

1.1

1.0

F1LS

0.9

♂ 0.8 ♀ NBF BF I

Figure 3.15 A plot of femur 1 length shape by population type and by sex shows that the Mormon crickets collected at DM and UR (I) were intermediate in this character shape between the NBF and BF population types (ANOVA: Population Type: p<0.0001, Sex: p<0.0001). Females of all three population types had significantly longer relative front femurs than males.

0.9

0.8 RWS

0.7

♂ 0.6 NBF BF I

Figure 3.16 Right Wing Shape (RWS) is the ratio of the square root of the surface area of the right wing divided by the geometric mean. A plot of male RWS by population type shows that NBF males, despite being the smallest bodied, had the largest relative right wings. The intermediate population (I) was intermediate in this character shape, and BF males had the smallest right wings relative to body size (ANOVA: p<0.0001).

0.35

0.30

MIS 0.25

0.20

0.15 ♂ NBF BF I

Figure 3.17 Mirror shape is the ratio of the square root of the mirror surface area divided by the geometric mean. A plot of MIS by population type shows that NBF males had the 58

largest mirrors relative to body size, followed by I males and BF males (ANOVA: p<0.0001).

Morphological Shape Size Differences by Sex and ANOVA Population Type Head Width Shape 12>3456 P<0.0001 Head Length Shape 12>3456 P<0.0001 Maxilla Width Shape 123456 P=0.1754, NS Pronotum Width Shape 123456 P=0.1737, NS Pronotum Height Shape 5126>34 P<0.0001 Pronotum Length Shape 1>35>246 P<0.0001 Ear Length Shape 2>51>346 P<0.0001 Femur 1 Length Shape 4>3>6251 P<0.0001 Femur 2 Length Shape 4>36>521 P<0.0001 Femur 3 Length Shape 24>31>56 P<0.0001 Femur 3 Width Shape 125346 P=0.0186 Tibia 1 Length Shape 3>4>6>5>21 P<0.0001 Tibia 2 Length Shape 3>4>6>521 P<0.0001 Tibia 3 Length Shape 4>3>2165 P<0.0001 Tarsus 1 Length Shape 34>2156 P<0.0001 Tarsus 2 Length Shape 34>2156 P<0.0001 Tarsus 3 Length Shape 123456 P=0.9999, NS Right Wing Length Shape NBF>I>BF P<0.0001 Right Wing Width Shape NBF>I>BF P<0.0001 Right Wing Shape NBF>I>BF P<0.0001 Mirror Length Shape NBF>I>BF P<0.0001 Mirror Width Shape NBF>I>BF P<0.0001 Mirror Shape NBF>I>BF P<0.0001

Table 3.13 Shape differences in morphology by sex and population type are shown above (1=NBF males, 2=NBF females, 3=BF males, 4=BF females, 5=I males, and 6=I females). The results are presented in descending order based on size differences and the results of post hoc Tukey tests. Non significant differences between the sexes and population types are indicated with an underline. P values of the ANOVAS by population type are also provided in the table. Wing shapes are reported for males only.

RESULTS: CORRELATIONS BETWEEN MORPHOLOGY AND MOVEMENT

RATE

Each morphological character shape was compared to rate of movement using

pairwise correlation analysis, and tested post hoc with Bonferroni probabilities (Table

3.14). GM showed a significant positive relationship with rate of movement such that

larger bodied individuals moved the fastest (Figure 3.17). The larger bodied BF Mormon

crickets from ER moved the most rapidly followed by the intermediate population type from DM and the smallest NBF Mormon crickets from IM and KF were almost completely sedentary.

The radio-tracked NBF Mormon crickets from KF and IM moved 2.312m to

20.273m in an 18 hour interval for an average rate of (0.426 m/h). The intermediate

Mormon crickets from DM moved between 1.321m and 80.046m in five hours (for an average rate of 4.570 m/h). The BF Mormon crickets from ER moved between 25.540m and 817.933m in approximately 20 hours for an average rate of 18.532 m/h). The disparity in movement behavior matches the disparity in locomotive morphology between

BF and NBF Mormon crickets. As with calling behavior, the intermediate population

type exhibited movement behavior most similar to the NBF population type.

Not surprisingly, the locomotive character shapes F1LS, F2LS, TI1LS, TI2LS,

TI3LS, TA1LS, and TA2LS also had significant positive correlations with rate of

movement while the call-producing character shapes RWLS, RWWS, MILS, MIWS,

RWS, and MIS featured significant negative correlations with movement rate. HWS, 60

HLS, and PHS also featured significant negative correlations with rate of movement.

MWS, PWS, PLS, ELS, F3LS, F3WS, and TA3LS were not significantly correlated to movement rate (α=0.05).

9 GM

7 ER UR DM IM KF 6 0 10 20 30 40 50 RATE

Figure 3.18 A plot of the correlation between geometric mean (GM) and rate of movement in meters per hour by site shows that there was a significant positive correlation between GM and rate of movement (r= 0.50648, p= 0.00008).

1.4

1.3

F2LS 1.2

1.1 ER UR DM IM KF 1.0 0 10 20 30 40 50 RATE

Figure 3.19 A plot of the correlation between femur 2 length shape (F2LS) and rate of movement shows that the BF radio-tracked specimens from ER with the longest relative second femurs moved the most rapidly (r= 0.55965, p= 0.00001).

1.7

1.6

1.5 TI2LS 1.4

1.3 ER UR 1.2 DM IM KF 1.1 0 10 20 30 40 50 RATE

Figure 3.20 A plot of the correlation between tibia 2 length shape (TI2LS) and rate of movement shows that the BF individuals from ER with the longest relative second tibias also moved the most rapidly (r= 0.51712, p= 0.00005).

1.00

0.95

HWS 0.90

0.85 ER UR DM IM KF 0.80 0 10 20 30 40 50 RATE

Figure 3.21 A plot of the significant negative correlation between head width shape (HWS) and rate of movement shows that radio-tracked NBF Mormon crickets from IM and KF with the largest relative heads were almost completely sedentary while the smaller headed BF Mormon crickets moved much more rapidly (r= -0.43546, p= 0.00089).

Correlation Bonferroni Mean Coefficient (r) probabilities (p) Shape Value (µ) Geometric Mean 0.506476 0.000080 8.158203 Head Width Shape -0.435463 0.000891 0.869196 Head Length Shape -0.319493 0.017421 1.448443 Maxilla Width Shape -0.096955 0.481321 0.809321 Pronotum Width Shape 0.019949 0.885054 1.209389 Pronotum Height Shape -0.377853 0.004453 0.899181 Pronotum Length Shape -0.022579 0.870028 1.620507 Ear Length Shape -0.146800 0.284845 0.331551 Femur 1 Length Shape 0.539435 0.000021 0.975758 Femur 2 Length Shape 0.559653 0.000009 1.195097 Femur 3 Length Shape 0.222725 0.102167 2.713820 Femur 3 Width Shape 0.131757 0.337620 0.591247 Tibia 1 Length Shape 0.565944 0.000007 1.158062 Tibia 2 Length Shape 0.517124 0.000053 1.391949 Tibia 3 Length Shape 0.394191 0.002903 2.852639 Tarsus 1 Length Shape 0.436902 0.000853 0.730799 Tarsus 2 Length Shape 0.515458 0.000056 0.775028 Tarsus 3 Length Shape 0.135701 0.323225 1.032010 Right Wing Width Shape -0.571892 0.002270 0.619824 Right Wing Length Shape -0.613274 0.000864 0.749932 Mirror Width Shape -0.637676 0.000458 0.415452 Mirror Length Shape -0.626233 0.000621 0.445860 Right Wing Shape -0.424077 0.030842 0.725434 Mirror Shape -0.570091 0.002361 0.233667

Table 3.14: Correlation Analysis The pairwise correlations between rate of movement and morphometric shape variables are presented above. Pearson’s r and Bonferroni probability values are included in the table as well as the mean shape values (in mm).

DISCUSSION

It was established in the preliminary study of morphology in Mormon crickets that BF Mormon crickets were larger overall than NBF Mormon crickets, that the degree

of sexual size dimorphism in the BF population type was reduced, and that there were at

least four characters that featured differences in shape in addition to these size differences

(Chapter II). Here we investigated additional morphological characters that varied in

shape with size differences between BF and NBF Mormon crickets. The results of this

study indicated 19 characters with significantly different character shapes by population

type using Mormon crickets that were collected in the summer of 2008.

There were several notable differences that emerged in this study using the 2008

data which were possibly related to the differences in the geometric means that were

chosen for the analyses. In Chapter II, there was a very highly significant interaction

effect between sex and population type for the geometric mean, which indicated that NBF

Mormon crickets were more sexually dimorphic in the geometric mean than BF Mormon

crickets. The 2008 results showed that BF and NBF Mormon crickets were equally

sexually dimorphic as estimated by the GM and the presence of a non-significant

interaction effect. In Chapter II, BF Mormon crickets also had wider relative maxillae

and heads than NBF Mormon crickets and females had wider relative maxillae than

males. However, in this study, MWS was not significantly different between population

types or by sex. Head width differences were reversed in the 2008 study, with NBF 66

Mormon crickets featuring wider heads than BF Mormon crickets. Additionally, the F3 in Chapter II was found to be relatively longer in BF Mormon crickets and in females of both types, however, F3LS was found to maintain geometric similarity by population type in the 2008 study.

One possible explanation for these differences is that the specimens used in

Chapter II were different from those collected in 2008. The sample of Mormon crickets used in Chapter II came from eleven different locations over several years, and there could be enough variation between the samples to cause a disparity in the results for the size and shape variables. This may also help to explain the difference in the degree of sexual size dimorphism between population types in the two studies. The specimens collected in 2008 were collected from late June to early July, and the presence of late instars in the populations where specimens were sampled indicated that the adults collected for this study were recently emerged adults. If these specimens had been collected later in the season, their weights may have been substantially higher which would have influenced the GM. Weight was not factored into the GM in the Chapter II analyses, so this explanation seems unlikely. It is more likely that the GM used in

Chapter II did not convey overall size information as effectively as the geometric mean used in 2008, and that BF and NBF Mormon crickets do not differ significantly in the degree of sexual size dimorphism as was previously indicated. This is unexpected based on the difference in mating patterns and the observed sex role reversal seen in BF populations, and an explanation is still lacking for why the two population types would 67

exhibit similar patterns of sexual size dimorphism when there are such striking differences in mating behavior.

Another possible explanation is that the GM used in Chapter II was constructed from only the four available characters. A GM should ideally contain pertinent information to the study question, and in this case, I was interested in comparing each character to the best possible estimate of overall body size (Mosiman 1970, 1975,

Mosiman & James 1979, Vinyard 2008). The GM used for the 2008 data was carefully chosen to include some measure of body weight and three measures each from the head, pronotum, and legs. While this GM may not completely capture body size, it arguably does so to a greater extent than a GM constructed using two head measures, a measure of the pronotum, and one out of six legs such as the GM from Chapter II.

In order to compare the 2008 results to the Chapter II results, I constructed a GM from the 2008 specimens using the same equation from Chapter II:

(4√(APLxMWxHWxAFL).

I then created shape ratios for the 2008 specimens using this GM as the

denominator, and tested the results with two way ANOVA (α=0.05). Not surprisingly, all

four characters including MWS and F3LS were found to be very highly significantly

different by population type and by sex just as they were in the Chapter II analyses.

These results supported the arguments warning about the importance of carefully

selecting characters for a GM (Mosiman 1970, 1975, Mosiman & James 1979, Vinyard

2008). 68

The principal component analysis of size and shape versus shape alone indicated

that while less of the overall variance in the sample was related to shape than to size and

shape, there was still substantial shape variation between population types to be

investigated. While Mormon crickets vary greatly in size, they clearly also vary greatly

in shape and it is likely that several of these shape differences reflect differences in

functional abilities. While the shape ratios constructed with the GM in the denominator

assist in describing shape relative to overall size, shape ratios that contain a

biomechanical standard in the denominator are critical for describing the functional consequences of shape (Vinyard 2008). This study was focused more on understanding the relationships between size and shape and provided very little contribution to the

understanding of the functional consequences of shape differences in Mormon crickets.

However, by identifying significant shape differences between population types, this has

hopefully laid the foundation for investigating the functional consequences of shape

variation in Mormon crickets.

Calling behavior was only qualitatively described in this study , however,

previous studies have shown that NBF Mormon cricket males call longer and more

intensively than BF males (Bailey et al 2007b). Differences in the shape ratios for wing

morphology were what we expected based on the previously quantified calling

differences. For example, NBF males were expected to have larger relative wings with

larger relative mirrors for producing a more intense sound and the results were consistent

with this hypothesis. In fact, NBF Mormon crickets featured longer, wider, and greater

overall area of wing and mirror shapes relative to body size than BF Mormon crickets. 69

Further, the length of the pronotum, which is expected to act as a speaker cabinet in the amplification of sound was also greatest relative to body size in the NBF Mormon cricket males. These results were consistent with what was predicted based on the known functional significance of wing form and the observed differences in calling structure between BF and NBF Mormon crickets (Bailey et al 2007b).

Previous work describing wing morphology in Mormon crickets looked at absolute size differences and concluded that NBF males had smaller elytral surfaces and smaller mirrors, and carrier frequency (Cf) was found to vary negatively with mirror surface area (Bailey et al 2007b). NBF males featured a higher Cf independent of mirror size which is not what we would expect based on the relationship between mirror size and Cf (Bailey et al 2007b). These unexpected results may be related to the failure to take into account shape differences, or relative size in the wing and mirror areas in Mormon crickets. For example, NBF Mormon crickets had smaller wings and mirrors because they were smaller bodied, however, when we measured wings and mirrors relative to the

GM, the NBF wing features were relatively larger than the BF wing features. These results were consistent with the expected role of mirror size in influencing call volume, or intensity (Bailey et al 2007b).

Ear length shape (ELS) was identified as a variable that demands further functional investigation which could not be achieved with this study. ELS was especially interesting because of the reverse in sexual dimorphism that was seen between BF and

NBF Mormon crickets. This may be related to the role of hearing in NBF females who are solitary and must seek out calling males with territories, however, this would not 70

explain why ear size in BF males would be relatively greater than in BF females. It is

interesting to speculate that this may be related to the role of sound and male calling (and listening) behavior in band formation and cohesion, however, this is yet to be tested in the field.

Additionally, there is more work to be done to explain the functional

consequences of head shape variables including head width, head length, and maxilla

width. MWS showed geometric similarity in BF and NBF Mormon crickets and these population types are expected to have differing diets based on differences in habitat type and population density. Little is currently known about natural dietary differences in

Mormon crickets , however, it was intended that the morphological descriptions provided in this study would assist in ultimately explaining the functional consequences of shape differences as they relate to feeding behavior. For example, while NBF Mormon crickets had wider and longer heads than BF Mormon crickets, MWS remained isometric between these population types. How does a shorter and narrower head relative to maxilla influence the differing functional requirements in BF Mormon crickets?

Vincent (2006) looked at sex-based differences in head shape and diet in the

Eastern lubber grasshopper, and found a strong correlation between head width and width

of foliage consumed. Females were observed having wider relative heads and consuming wider and thicker foliage (Spartina alterniflora). The author strongly suggested that sex- based shape differences in head morphology be taken into account in studies examining diet in insects. Further suggestion was made to incorporate the analyses of nutritional differences in addition to the plant morphology when attempting to draw conclusions 71

about the evolution of shape differences in insect morphology. There are plans to

conduct such analyses that would include stable isotope differences between male and

female BF and NBF Mormon crickets (Lorch unpublished data). The differences in

Nitrogen signatures may help to explain the differences in trophic levels between BF and

NBF Mormon crickets. Additionally, the correlations between head morphology and

Nitrogen signature may help to explain the functional abilities of these morphological shapes.

The differences in locomotive morphology between BF and NBF Mormon crickets appeared to reflect differences in movement behavior. It has been well documented that BF Mormon crickets move significantly farther and more rapidly than

NBF Mormon crickets. The data presented here established that in addition to moving more rapidly, BF also feature significantly longer relative front and middle femurs, tibias, and tarsi. These characters were also strongly correlated with rate of movement in this study, which may indicate that there is a functional relationship between these morphological characters and movement rate. If these features represent efficient movement morphology, then females in both types, with longer locomotive features

relative to body size, would appear to be more efficient than males in both population

types. In NBF populations, females are presumed to be more mobile than males as they move in search of males with territories. I tested the effects of sex and population type on movement with a two way ANOVA (α=0.05) and there was no significant effect of

sex on rate of movement which leaves little explanation for why females would have

longer femurs, tibias, and tarsi than males if these features represent efficient movement 72

morphology. There is more work to be done in this area of functional morphology in

Mormon crickets, as well as the development of appropriate shape ratios for describing

the functional consequences of shape may assist with this problem.

The similarity in shape of the F3 length and width by population type despite size

differences as estimated by the geometric mean are particularly interesting, especially since F3 length and width were not correlated with rate of movement. We expected a smaller F3 shape in the BF population type, based on the known differences in speed of movement, however, it is possible that this large, broad hind femur, which is required for efficient jumping, is too highly constrained for this action to differ in shape between the population types. The shape of the F3 may not change out of necessity for predation avoidance or some other selective pressure experienced by Mormon crickets in all of the population types. Interestingly, the hind tibia is relatively larger in the BF population type, and the functional consequences of this morphological design would be very interesting to investigate further between the population types. Unlike the hind femur, the hind tibia was found to be positively correlated with rate of movement, and given that the hind femur is geometrically similar and the hind tibia is not, there may be implications for this morphological design that influence rate of movement with or without compromising jumping ability.

The Mormon crickets sampled from eastern Utah at Diamond Mountain were clearly intermediate in morphology although in movement and calling behavior they more closely resembled the NBF population type in 2008. Interestingly, while the overall body size of the intermediate population type was more similar to the BF population type, 73

21 shape ratios were shown to be significantly different than either population type.

Mormon crickets that have been collected at this eastern part of the BF range in eastern

Utah in the past have genetically grouped with the BF type despite population density and behavior that more closely resembles NBF Mormon crickets. The radio-tracked intermediate Mormon crickets from Diamond Mountain also clearly showed movement behavior that more closely resembled the NBF population type, and the male calling was qualitatively more similar to NBF calling as well.

Since the role of plasticity in influencing Mormon cricket behavior and morphology is not currently known, these intermediate populations may be helpful in looking at questions related to plasticity. Are morphology and behavior plastic in

Mormon crickets, or simply behavior, or neither? If Mormon crickets are fixed in morphology then perhaps only the band-forming behaviors such as rapid, cohesive movement and relatively shorter, less intense male calls are plastic and induced by environmental stimuli such as population density and food abundance. What are the selective pressures influencing these differences in morphology between Mormon cricket populations? Do BF, NBF, or intermediate Mormon crickets typify the ancestral state of this species, or does each type feature uniquely selected traits since their genetic divergence during Pleistocene glaciations? What are the dietary differences between population types, and how do these differences relate to shape differences in morphology?

Other new questions have arisen based on these results including questions about the patterns of integration between morphological characters and the evolution of 74

different integration patterns in Anabrus simplex. All of these questions relate to the central theme of developing a better understanding of the evolution of phenotypic variation in Mormon crickets. Chapter III has provided useful descriptions of morphological shape differences and their relationships with rate of movement, however, there is a great interest in understanding how these changes have evolved.

CHAPTER IV: PATTERNS OF MORPHOLOGICAL INTEGRATION IN MORMON

CRICKETS

INTRODUCTION

Morphological integration was developed based on the concept that characters with functional or developmental relationships tend to be correlated and evolve as a unit

(Olson & Miller 1958, Cheverud et al 1989). More recent theoretical studies of stabilizing selection on functionally related characters highlighted that these functionally and developmentally related characters may also become genetically correlated which supports the earlier ideas of the process of character complex evolution (Cheverud et al

1989). A typical goal of these studies includes the comparison of integration patterns for understanding species divergence, and more specifically the evolutionary processes underlying particular character complexes (e.g. Marroig et al 2003). The effects of factors such as body size, diet, and locomotion on differences in covariance structure can also be determined using these methods of matrix comparisons (e.g. Marroig & Cheverud

2005, Vinyard 2007).

While genetic correlations are useful for investigating the mechanisms of evolutionary integration, they are difficult to estimate and often require extensive breeding experiments. The study of phenotypic correlations, the sum of genetic non- genetic correlations, potentially allows for a broader range of evolutionary questions to

75 76

be addressed, although with less specificity. Furthermore, phenotypic correlations may contain more information about the underlying evolutionary processes driving phenotypic change since the phenotype is the direct target of selection (Burger 1986, Cheverud et al

1989). Cheverud (1988) and others (e.g. Roff 1995, 1996, Koots & Gibson 1996) discovered that in cases where genetic and phenotypic correlations of morphological traits were available, there were similarities between genotypic (G) and phenotypic (P) matrices across a wide range of heritabilities so long as the genetic correlations were closely estimated. Therefore, it is often acceptable to substitute phenotypic correlations for genetic correlations based on congruence when genetic correlations are unavailable.

However, Turelli (1988) and Wagner (1990) have pointed out that other comparisons of genetic and phenotypic correlations have revealed significant differences between these matrices.

Wagner implored that the comparative analysis of variation in morphological integration be utilized in order to address the question of how correlations change and specifically, how they contribute to phenotypic evolution. The very early stages of describing and interpreting the patterns of integration in Mormon crickets were established in this thesis with the goal of describing the variation in patterns of integration by population type.

For Mormon crickets, morphological integration techniques were employed as an additional way to describe and understand the broad range of intraspecific phenotypic variation and how the population types have diverged in morphology including the morphological interrelationships since the genetic divergence of the BF and NBF 77

population types approximately two million years ago (Bailey et al 2005). This falls under the sub-topic of morphological integration termed evolutionary integration

(Cheverud 1996), which can help to describe the coordinated evolution of morphological

traits. This process is thought to occur because the traits are inherited together or because

they are selected together, though inherited separately (Felenstein 1988).

Techniques in morphological integration may be an especially useful way to

investigate evolutionary questions in Mormon crickets since their eggs have never been

reliably hatched in a laboratory, and since outbreak conditions are not easily simulated in a laboratory. In other words, breeding experiments would be especially difficult to conduct for this species, and P matrices may be the best possible estimate of morphological correlations in Mormon crickets. Further, these techniques have been employed in order to investigate whether different populations of Mormon crickets exhibit different organization, or integration of morphological features. This is one possible explanation for how the shape differences identified in Chapter III may have arisen in different population types and this explanation does not rely on estimates of G matrices.

STUDY QUESTIONS

The two main questions addressed in this study were: 1. Do Mormon crickets exhibit different patterns of morphological integration between population types (e.g. 78

Wagner 1990)? 2. If so, how has the covariance structure changed with respect to size

and shape? Hypotheses of different levels of integration were tested between male and female BF Mormon crickets, NBF Mormon crickets, and intermediate Mormon crickets,

and were based on the assumed strength of integration between certain traits as well as

the supposed functional or developmental relationships among characters. Characters

that comprise the head were assumed to be functionally and/or developmentally related,

as well as the leg characters, and the characters of the pronotum, each as distinct

functional and/or developmental groups. Comparisons of the matrices of raw variables

with the different hypotheses of integration were made as well as comparisons of the matrices of shape variables with the different hypotheses of integration in order to

address the question of how the patterns of integration changed with respect to size and

shape differences. To compare patterns of variation in covariance structure we tested

seven alternative hypotheses of integration as follows:

H1-Local Integration: Correlations of 1 within each assumed functional group (head,

pronotum, and legs), 0 between groups

H2-Pronotum Isolated Integration: Correlations of 1 within head and leg measurements,

and within pronotum measurements, 0 between head or leg and pronotum measurements

H3-Legs Isolated Integration: Correlations of 1 within the head and pronotum

measurements and within all leg measurements, 0 between head or pronotum and leg

measurements 79

H4-Front and Middle Legs Isolated Integration: Correlations of 1 within F3, TI3, and

TA3 and within front and middle legs, head and pronotum measurements, 0 between each group (i.e. between head or pronotum, and other leg measurements, and between the other leg measurements and F3, TI3, and TA3)

H5-NBF Larger Integration: Correlations of 1 within features that were relatively larger in the NBF population type (HLS, PHS, PLS), 0 between these features and all other features, 0 within all other features

H6-BF Larger Integration: Correlations of 1 within features which were relatively larger in the BF population type (F1, F2, TI1, TI2, TI3, TA1, TA2, TA3), 0 between these features and all other features, 0 within all other features

H7-Hind Limb Isolated Integration: Correlations of 1 within head measurements, within pronotum measurements, within F1, F2, TI1, TI2, TA1, TA2 measurements, and within

F3, TI3, TA3 measurements, 0 between these groups

We expected NBF Mormon crickets to exhibit local integration, or strong correlations within the assumed functional groups such as features of the head, features of the pronotum, and features of the legs. If the NBF morphotype is the ancestral state in this species, these features may be more highly constrained, and less subject to changes via changes in correlation structure due to strong correlations within assumed functional groups. The more derived morphotype may be the type that features either distinct groupings of characters that are not expected to be developmentally related, or overall less highly constrained, or weaker associations between traits. BF Mormon crickets were 80

not expected to fit H1 based on the presumption that the shape differences seen in the BF

type are derived. Since these evolutionary relationships are not currently known, we hoped this study would reveal some insight as to which population type is more derived

using these criteria as the basis.

BF males and females were expected to fit the Legs Isolated Integration

hypothesis (H3) and the Front and Middle Legs Isolated Integration hypothesis (H4).

Unlike the Hind Limb Isolated Integration hypothesis (H7) which isolated the entire hind

limb, H3 featured strong correlations between all leg features, and isolated the leg

features from the head or pronotum features. H4 isolated the front and middle legs as a

distinct group because they were found to be relatively longer in the BF type (Chapter

III). This was presumably due to differences in the ability to walk rapidly over long

distances as seen in the BF population type. The NBF type was expected to also fit H7

and to have a hind limb that is highly integrated for jumping.

In the sex role reversed populations, females must compete for mates, and in NBF

populations, males must compete over females. We also predicted that the sex expected

to adapt to mate preference would be less constrained, or in other words, feature weaker

correlations between traits. Regardless of the best fit of hypothesis for BF females and

NBF males, these two groups were also expected to exhibit similar patterns of integration

based on the similar sexual selection pressures expected to be faced by both groups.

In order to explore the differences between raw correlations and shape

correlations, we compared the raw and shape matrices to each hypothesis of integration.

We expected that the NBF population type would fit the Pronotum Isolated hypothesis 81

(H2) and the NBF Larger Integration hypothesis (H5) when the shape matrices were compared based on the findings in Chapter III. Likewise, we expected the shape matrices for the BF males and females to fit with the BF Larger Integration hypothesis (H6) also based on the findings from Chapter III. When the raw matrices were compared, we did not expect the NBF type or the BF males or females to fit these hypotheses, thereby showing that the shape matrices should correspond to hypotheses of integration that are based on observed shape differences.

The intermediate type was more similar in body size to the BF type , however, the morphological shape differences of the intermediate type were distinct from either BF or

NBF Mormon crickets, so it was much more difficult to predict which integration pattern they would fit best. Their inclusion in the hypothesis testing was exploratory, and only a posteriori explanations are discussed for this population type.

We also tested two hypotheses of integration in males only which were based on the contact call hypothesis for cohesive movement in Mormon crickets (Chapter I). The shape matrices included the wing measurements. We compared the shape matrices of males of each population type to the following hypotheses of integration that test differences in the levels of integration within leg and wing characters by population type:

Weak Wing-Leg Integration: Correlations of 0.5 within leg/wing measurements, 0 between leg/wing and head/pronotum measurements

Strong Wing-Leg Integration: Correlations of 1 within leg/wing measurements, 0 between leg/wing and head/pronotum measurements 82

BF male Mormon crickets were expected to fit a pattern of integration characterized by stronger correlations (1) within leg and wing features than between the legs or wings and any other group of features based on the contact call hypothesis for cohesive movement (see Chapter I). Stronger correlations within leg and wing features would support the hypothesis that these features are strongly integrated and evolve together to perform a common function. Regarding leg and wing integration, it was hypothesized that the BF males use sound to form and maintain cohesive movement, and that differences in wing shapes would be correlated to differences in leg shapes in this population type. Therefore, the Strong Wing-Leg Integration hypothesis was expected to be significantly similar to the observed correlation matrix for BF males. NBF males were expected to differ from the BF males in this pattern of integration, and to better fit the

Weak Wing-Leg Integration hypothesis, which featured weaker correlations (0.5) within leg and wing features. This population type was not expected to have a functional relationship between leg and wing features because they do not feature cohesive movement patterns. Again, intermediate males were included for exploratory purposes.

METHODS

Phenotypic correlation matrices were constructed using the raw morphometrics that were collected for Chapter III and the shape variables that were calculated by 83

dividing the raw variables by the geometric mean (See Chapter III for methods on morphometric measurements and the calculations for the geometric mean and shape ratios). A priori hypotheses of integration patterns were developed and then tested using quadratic assignment procedures, or Mantel tests which test the statistical significance of the similarities between matrix structures (Mantel 1967, Cheverud et al 1989, Wagner

1990). Using this technique, each hypothesis was expressed as a matrix of the presumed associations between characters. The hypotheses were then compared to the observed correlation matrices with correlation analysis and Mantel tests were employed to test for significant matrix correlations after the matrices were subjected to 9,999 replicate permutations of comparisons (α=0.05).

We compared males and females of the BF population type to the seven hypotheses of integration , however, sample sizes were too small for NBF males and females and intermediate males and females to achieve reasonable estimates of covariation structure. Values for NBF and intermediate males and females were mean- centered to the mean values for females of each population type for the matrix comparisons to the seven hypotheses of integration. Mean-centering NBF and intermediate population types allowed us to combine male and female data so that sample sizes were sufficient and to remove sex effects prior to the analysis of covariation structure.

To test the hypotheses of integration related to the contact call hypothesis for cohesive movement, matrix comparisons were made using correlation matrices of the 84

shape variables only and included the wing shape variables. Only males were tested

because wing measurements were not collected for females.

We compared raw and shape matrices to the seven hypotheses of integration patterns in order to investigate differences in the patterns of integration between raw and shape variables by population type. Since sample sizes were large enough to test BF males and females separately, we were able to distinguish between male and female raw and shape matrices and how they compare to the alternate hypotheses of integration.

RESULTS

The evidence of striking morphological, behavioral, and genetic differences between Mormon cricket population types (Chapters I, II, and III) suggested that there may be intraspecific differences in the patterns of integration. Some slight differences between male and female BF Mormon crickets and between population types were detected although they were not always as predicted. Additionally, for all three population types, there were differences in the patterns of integration when we compared raw and shape matrices to the hypotheses of integration.

Regarding the comparisons of the correlation matrices of the raw variables, H3

(Legs Isolated Integration) was the best hypothesis for BFF while H4 (Front and Middle

Legs Isolated Integration) was the best hypothesis for BFM, intermediate, and NBF

Mormon crickets. For the comparisons of the shape variable matrices to the hypotheses 85

of integration, H1 (Local Integration) was the best fit for BFF and the NBF population type, and H7 (Hind Limb Isolated Integration) was the best hypothesis for BFM and the intermediate population type (Table 4.1).

Surprisingly, H5 (NBF Larger) and H6 (BF Larger), which were based on shape differences found in Chapter III, were not the best fit for the NBF shape or BF shape matrix comparisons, although H6 was significantly correlated to the shape matrices for

BF males and females. Also unexpectedly, the Weak Wing-Leg Integration hypothesis was the best fit for BFM and intermediate males (Table 4.2). The sample size for NBF males was too small to achieve reasonable estimates of covariation so we were unable to test whether BF and NBF males differ in patterns of covariation that include wing shapes.

H1 H2 H3 H4 H5 H6 H7 BFFR 0.3758 0.3462 0.3921 0.2760 0.0086 0.2270 0.2426 (0.009) (0.007) (0.004) (0.018) (ns) (ns) (0.032) BFFS 0.5927 0.4655 0.5070 0.3186 -0.1044 0.4853 0.3620 (0.009) (0.005) (0.015) (0.011) (ns) (0.018) (0.017) BFMR 0.0420 0.0640 0.1168 0.2781 0.1071 -0.0989 0.1896 (ns) (ns) (0.049) (0.040) (ns) (ns) (0.019) BFMS 0.3682 0.3348 0.2841 0.2642 -0.1443 0.3785 0.3977 (0.018) (0.048) (0.028) (0.045) (ns) (0.034) (0.004) IR 0.0114 0.0449 0.1002 0.3797 0.1875 0.0211 0.2865 (ns) (ns) (ns) (0.017) (ns) (ns) (0.006) IS 0.3172 0.0816 0.2516 0.3575 0.0561 0.4587 0.4955 (0.032) (ns) (ns) (0.010) (ns) (0.007) (0.005) NBFR 0.0902 -0.0241 0.1282 0.2902 0.1161 -0.0999 0.1240 (ns) (ns) (ns) (0.036) (ns) (ns) (ns) NBFS 0.3637 0.1991 0.2677 0.2247 -0.0779 0.3307 0.2926 (0.043) (ns) (0.037) (ns) (ns) (0.037) (0.041)

Table 4.1 Matrix comparisons between the raw and shape matrices with the seven integration hypotheses are shown above with (p values). Non-significant p values are indicated by (ns). BFFR=Band-forming females raw, BFFS=Band-forming females shape, BFMR=Band-forming males raw, BFMS=Band-forming males shape, IR=Intermediate raw, IS=Intermediate shape, NBFR=Non-band-forming raw, NBFS=Non-band-forming shape. The red highlighted rm values indicate the strongest correlation for each class type, and all significant rm values are in bold.

Weak Wing-Leg Strong Wing- Integration Leg Integration NBFMS 0.1673 (ns) 0.1340 (ns) IMS 0.2742 0.1161 (ns) (0.003) BFMS 0.4166 0.3033 (ns) (0.003)

Table 4.2 Matrix correlations of the shape (S) matrices and (p values) between each sex/population type class and the four integration hypotheses are shown above (ns=non-significant). Sample sizes for NBF males and females, and intermediate males and females were < 25 which may explain the non-significant results for those classes. H3 and H4 include the correlations of wing morphology, so females were not included in the analyses.

DISCUSSION

In the comparative analysis of morphometric correlation matrices, BF, NBF, and

intermediate Mormon crickets appeared to have similar patterns of morphological

integration which may also be described as an evolutionarily stable pattern of integration

within this species. The Local Integration hypothesis (H1) was able to describe the

pattern of integration in all three population types when the correlation matrices of the

shape variables were compared to the different hypotheses of integration. H1 was also

the best fit for BF females and the mean centered NBF population type. This pattern of

strong correlations within functional groups and weaker correlations between groups is consistent with the notion that characters within the same assumed functional or 88

developmental group are highly correlated. For example, all of the leg characters (F1,

F2, F3, TI1, T2, TI3, TA1, TA2, and TA3) were expected to be highly correlated because

of their presumed developmental and functional relationships, whereas leg characters were expected to be less strongly correlated to the head and pronotum characters because of their presumed differential developmental and functional relationships. The observed pattern of local integration among all three population types indicated that in the characters being compared, Mormon crickets from different populations appear to be modular in the same way. These results are not totally surprising since these were

intraspecific comparisons, although they differed from the prediction that BF and NBF

would differ on this level of trait organization. In the end, morphological shape

differences and behavioral differences observed within this species are not necessarily

influenced by changes in modularity or integration and this may be additional evidence

that the species should not be phylogenetically split by population type despite high

levels of phenotypic variation in morphology and behavior.

BF and intermediate males appeared to fit the Weak Wing-Leg Integration

hypothesis rather than the Strong Wing-Leg Integration hypothesis as predicted. These

hypotheses were based on the concept that the legs and wings of insects share

developmental origins, and are therefore more strongly correlated than either are to other

developmental groups. The Weak Wing-Leg Integration hypothesis featured weaker

correlations (0.5) between the developmental groups than the Strong Wing-Leg

Integration hypothesis (1), and these findings may suggest that while the leg and wing

characters are somewhat correlated in Mormon cricket males, these associations are not 89

as strong as the relationships within local groups such as measurements within the head or within the pronotum. Unfortunately the sample size for NBF males was too small to distinguish which of these hypotheses was the best fit for this group. We predicted that

BF and NBF Mormon cricket males would differ in this pattern of integration based on

the contact call hypothesis for cohesive movement, (Chapter I) however, a larger sample

size is necessary in order to test this convincingly.

Slightly differing patterns of integration emerged between BF males and females,

and between population types. For instance, BF males and females showed some

disparity in their correlations with the alternate hypotheses of integration whether raw or

shape matrices were compared. H4 was the best fit for BF males and H3 was the best fit

for BF females when raw matrices were compared. This is contrasted with the results for

the comparison of the BF shape matrices, in which the BF males unexpectedly best fit H7

and BF females unexpectedly best fit H1. In other words, BF males and females appear

to have differing patterns of limb integration which were not easily predicted based on

shape differences or movement behavior (Chapter III), indicating the need for more

study.

Hind limb characters are presumed to be more strongly related to jumping and

kicking abilities, since this is the limb most heavily used in the catapult system of

hopping that is seen in katydids, grasshoppers, and other orthopterans. They are also

used to fend off potential cannibals that often attack from behind. Based on the analyses

in Chapter III, the F3 is “isometric” by population type, which may indicate that this

shape is more highly conserved, however, females had larger relative F3s in all three 90

population types. Females, who are relatively larger, may have less to fear from cannibalism and may need more coordinated force from all limbs to move in the band forming populations. Relatively smaller males, on the other hand, may have relatively more to fear from cannibalism and may emphasize jumping and kicking over rapid movement. Since these particular ecological differences only exist in the BF population type, we expected that NBF and intermediate males and females would have similar correlations with H7 that would differ from the BF population type. Unexpectedly, BF males and females and mean centered intermediate Mormon crickets fit H7 whether raw or shape matrices were compared, however, mean centered NBF Mormon crickets did not. This is not easily explained with the available information.

The NBF population type differed in which hypotheses best fit when the raw and shape matrices were compared to the different hypotheses of integration. They did not fit best with H2, H5, or H7 as predicted. The raw variable matrices for the NBF type only fit H4, which was completely unexpected. The shape matrices for the NBF type best fit

H1 as predicted, however it was surprising that the NBF type and the BF females both fit best with this pattern of integration. Whether the raw or shape matrices were compared for the intermediate population type, they best fit the same hypotheses as the BF males.

The raw variable matrices for the intermediate population type best fit H4 making them more similar to the BF males, and the shape variable matrices for the intermediate population type best fit H7 also making them more similar to the BF males. This pattern is not very easily explained with the available data (Chapter III). Based on movement patterns, we would expect NBF and intermediate Mormon crickets to be more similar, 91

however, genetic data indicate that BF and intermediate Mormon crickets are more

closely related (Bailey et al 2005).

Several important observations were made as a result of these tests including the

importance of having much larger sample sizes, an outgroup for making interspecific as

well as intraspecific comparisons, and sampling a larger number of morphometrics for

making comparisons within and between functional or developmental groups of

characters. The sample size for the NBF males was far too small to be able to test the

hypothesis of a functional difference in modularity between population types which

would have provided insight to the contact call hypothesis. Small sample sizes for the

NBF and Intermediate population types also placed constraints on our ability to test sex

differences in integration patterns by population type. By adding more characters to the

matrices, more comparisons could be made within functionally or developmentally

related groups by population type, which would enhance our understanding of modularity

in Mormon crickets. We expected the major functional groups to feature the type of

relationships that they did, however, more detailed information about the interrelationships within functional groups would aid in our understanding of how these

characters vary and covary with one another, and how those patterns may differ between

population types based on selection for those differences.

Above I listed some of the interests for the future study of integration patterns in

Mormon crickets. Additionally, there is some interest in directly testing hypotheses that

would address questions of phenotypic plasticity in Anabrus. Specifically, I would like

to investigate whether and how the patterns of integration in a phenotypically plastic 92

species differ from the patterns of integration in a non-plastic species, and how Mormon cricket integration patterns compare to each of those species’ patterns. It is interesting that the large bodied intermediate population type, which is also genetically more similar to the BF population type exhibits behavior more similar to the NBF population type.

Perhaps the morphology in this group is fixed and only the behavior is phenotypically plastic, or perhaps only some morphological features are phenotypically plastic and are switched on by some environmental cue such as high population density and reduced food abundance. Close monitoring of these populations over the next several years may assist in making predictions about Mormon cricket outbreaks in this region, and whether this population type may exhibit BF characteristics under certain environmental conditions. Further, tracking the changes in integration patterns by population type over time may reveal changes in trait organization in response to ecological conditions including population density, diet, predation, and mating patterns.

CHAPTER V: CONCLUSION

“Measurements tell one almost nothing about the functional significance of differences between such animals. Qualitative as well as quantitative traits are involved. Likewise, ecologists can ascertain the sort of habitats in which the various species live, can try to find out what sort of water body or water chemistry each prefers (I’ve tried to do so myself), and can estimate numbers and how they change throughout the year. However, until it is known what the animals are actually doing, which calls for an understanding of their functional morphology, it is not possible to really understand their ecology.”

G. Fryer (1988) made these comments in a letter to Functional Ecology in an effort to point out that orthodox ecologists often ignore functional morphology, and that when combined with ecological data, morphological information can be very enlightening. Another critical observation by Fryer involved the differences in morphology of animals in the same group, and how those differences map onto differences in ecological niche space, a topic that formed the basis for the questions in this thesis. Many ecomorphological studies investigate patterns of morphological distributions as they relate to the environment or ecological community structure, assuming that the ecological roles of organisms can be inferred from morphology (Koehl

1996). The functional meaning of the morphological variables in question was the relevant area of interest in this study, and it has been investigated in an effort to shed more light on the evolution of phenotypic variation in the genus Anabrus. Hopefully when coupled with behavioral and ecological data, the investigation of morphological

93 94

differences between population types will aid in the pursuit of a more holistic

understanding of the causes of variation among Mormon crickets.

Mormon crickets, which can be a species with economic significance to humans under outbreak conditions, may require such thoughtful investigation as to include the functional relevance of morphology in their often devastating flightless migration.

Rather than considering morphology to be an inconvenient property of an ecological problem, the aim of this thesis was to describe Mormon cricket morphology in terms of shape differences and the evolutionary patterns of morphological integration in BF and

NBF populations. Since movement is a major behavioral difference between population types, we investigated locomotive morphology as it differs between these groups.

Likewise, since calling behavior has also been identified as a major behavioral difference between population types, wing morphology was described in terms of shape differences by population type and the potential functional consequences of the observed shape differences. Once shape differences were identified and discussed in terms of assumed function, the patterns of integration were examined in order to investigate how these changes in morphology may have occurred over evolutionary time.

Preliminary conclusions using four linear characters provided by the University of

Toronto showed that BF Mormon crickets were larger bodied than NBF Mormon crickets as estimated by a GM of these measures. Sexual size dimorphism in GM was more pronounced in NBF than in BF Mormon crickets with females being larger than males.

NBF Mormon crickets featured longer relative pronota, with NBF males having the longest relative pronota of the four groups. BF Mormon crickets had wider relative

maxillae and heads as well as longer relative hind femurs than NBF Mormon crickets, as

did females of each population type (Chapter II). The discovery of four characters that

varied in shape with body size differences between population types provided

encouragement to seek out additional characters in a systematic way that could provide

information about the functional relevance of shape differences in morphology.

Chapter III analyses were conducted using the GM of ten characters, which likely

gave a better estimate of body size than the GM used in Chapter II. This was supported

by a reanalysis of the shape ratios using a GM constructed using the same four variables

that were available in Chapter II. All four characters including MWS and F3LS were

found to be relatively larger in the BF Mormon crickets as they were in Chapter II.

Four out of 23 characters were “isometric” in shape between BF and NBF

Mormon crickets using the ten variable GM in the denominator of the shape ratios. For

MWS, PWS, F3LS, and F3WS, geometric similarity was preserved with size differences between the two main population types. In head, pronotum, and wing morphology, NBF

Mormon crickets showed a pattern of having increases in the size of these characters, while in locomotive morphology, BF Mormon crickets showed increases in the size of these characters, except for the four isometric characters (MWS, PWS, F3LS, and

F3WS).

This pattern of shape differences that emerged likely reflects the observed differences in calling and movement behavior between BF and NBF Mormon crickets,

(with the exception of head morphology that still requires further behavioral investigation involving nutritional analysis). For example, BF Mormon crickets are more than twice as

large as NBF Mormon crickets, and there are likely to be functional consequences of shape whether or not geometric similarity is preserved with size. Since the larger bodied

BF Mormon crickets feature a relatively equal sized F3 to NBF Mormon crickets, the functional ability of the F3 for jumping is likely to change because of the difference in body size and the geometric similarity of the F3. In other words, if the F3 operates similarly in BF and NBF Mormon crickets, you would expect BF Mormon crickets to have longer F3s due to their larger body size. Otherwise, it may be assumed that there are functional consequences of shape similarity despite body size differences. In this case, geometric similarity may result in differences in functional abilities, and these relationships deserve further attention in order to more fully understand the morphological differences as they relate to behavioral abilities. Likewise, as features such as the front and middle femurs and tibias are relatively enlarged in the BF population, it is unknown to what extent this difference enhances the locomotive ability of this population type. So far it is known that these locomotive features are strongly and significantly correlated with rate of movement, however there is more work to be done to investigate the functional consequences of such size related changes in shape.

Many unanswered questions remain with regard to the patterns of integration in

Mormon crickets. The preliminary investigation of the interrelationships between morphological characters (Chapter IV) revealed that when the shape matrices for all population types were compared to the different hypotheses of integration, they all shared a pattern of local integration. H6, the BF Larger hypothesis was also significantly correlated with the observed shape matrices of all three population types. While all three

population types featured significantly similar shape matrix correlations with H1 and H6,

there were also slight differences in the correlations between the hypotheses of

integration and the observed correlation matrices of the different population types. For

instance, BF female and NBF shape matrices best fit with H1 , however, BF male and

intermediate shape matrices best fit with H7, the Hind Limb Isolated hypothesis.

When the raw matrices for each type were compared to the hypotheses of

integration, H4, the Front and Middle Legs Isolated hypothesis was the best fit for BF

males, intermediate, and NBF Mormon crickets, but not for BF females. Additionally, neither H1 nor H6 were significantly correlated to the raw matrices of any population

type.

The NBF shape matrices were expected to best fit H5, the NBF Larger hypothesis

based on shape differences that were identified in Chapter III. The observed matrices for

NBF Mormon crickets were not significantly correlated to H5, however, they were

unexpectedly correlated to H6, the BF Larger hypothesis. Despite fitting the local

integration hypothesis, NBF Mormon crickets also unexpectedly fit the Legs Isolated

Integration hypothesis when their shape matrices were compared to this hypothesis, and

the Front and Middle Legs Isolated Integration hypothesis when their raw matrices were

compared. They were expected to fit H2, the Pronotum Isolated hypothesis based on

shape differences, however, the observed correlation matrices for NBF Mormon crickets

were not significantly correlated to H2.

Unfortunately, due to small sample sizes for the NBF males, the contact call

hypothesis could not be adequately tested in this study. For the preliminary test of matrix

comparisons between the shape variable matrices for males and the integration

hypotheses, the Weak Wing-Leg Integration hypothesis was the best fit for BF and

intermediate males. This indicated that the correlations between the leg and wing

characters were above zero but less than 1. This was unexpected based on the contact

call hypothesis, since this hypothesis predicted that the wing and leg characters would be

more strongly correlated if these two groups function and evolved in concert.

Unfortunately the pattern of integration for NBF males could not be tested in this study,

and further work will assess whether or not BF and NBF males differ with respect to leg and wing integration, and if so, what those relationships may mean.

In summary, several steps have been taken in this thesis to more accurately

describe Mormon cricket morphology and to combine empirical studies of behavior and morphology to describe the differences between population types. While previous studies have attempted to describe morphology in this species, their failure to account for size related differences has made it impossible until now to investigate the functional consequences of shape changes. With these much improved descriptions of Mormon cricket morphology and how shape differences vary by population type, we are closer to understanding the evolution of intraspecific phenotypic variation in Anabrus simplex and

to formulating more informed hypotheses regarding functional morphology in Mormon

crickets.

These preliminary studies of similarities and differences in the patterns of

morphological integration in Mormon crickets have shown that much more work is

needed in this area in order to understand differences in functional morphology and

evolutionary integration by population type. Ideally future studies of integration

involving this species will include other members of the genus such as Anabrus longipes,

a species that is also known to occasionally exist in outbreak form, as well as species that are known to have a gregarious or outbreak morph, and a species that does not have an outbreak morph. This thesis has hopefully helped to lay the groundwork for an extended comparative study of the evolution of phenotypic variation in katydids.

100

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