Ecology and Evolution of Dung Beetles

Contents

Preface

Acknowledgements

Contributing Authors

1 Reproductive Competition and Its Impact on the Evolution and Ecology of Dung Beetles

1.1 Introduction

1.2 Competition for mates and the evolution of morphological diversity

1.3 Competition for resources and the evolution of breeding strategies

1.4 Ecological consequences of intraspecific and interspecific competition

1.4.1 Niche expansion

1.4.2 Regional distribution and seasonal activity

1.4.3 Community dynamics

1.5 Conservation

1.6 Concluding remarks

2 The Evolutionary History and Diversification of Dung Beetles

2.1 Introduction

2.2 Scarabaeinae diversity and tribal classification issues

2.2.1 Dichotomiini and Coprini

2.2.2 Canthonini

2.2.3 Eucraniini

2.2.4 Phanaeini

2.2.5 Phanaeini + Eucraniini

2.2.6 Scarabaeini

2.2.7 Gymnopleurini

2.2.8 Eurysternini

2.2.9 Sisyphini

2.2.10 Onitini

2.2.11 Oniticellini

2.2.12 Onthophagini

2.3 Scarabaeine dung beetle phylogenies

2.4 The sister clade to the Scarabaeinae

2.5 The origin of the dung beetles

2.6 The oldest lineages and their geographical origin

2.7 Evolution of activity period

2.8 Evolution of feeding habits

2.9 Evolution of derived alternative lifestyles

2.10 Evolution of nidification: dung manipulation strategies

2.11 Evolution of nidification: nesting behaviour and subsocial care

2.12 Conclusions

2.13 Future work/gaps in knowledge

3 Male Contest Competition and the Evolution of Weapons

3.1 Introduction

3.2 Dung beetle horns as weapons

3.3 Functional morphology of horns

3.4 Horns as predictors of victory

3.5 Are beetle horns simply tools?

3.6 The evolution of horns: rollers vs. tunnellers

3.7 The evolution of horns: population density

3.8 The evolution of horns: sex ratio

3.9 Future work

4 Sexual Selection After Mating: The Evolutionary Consequences of Sperm Competition and Cryptic Female Choice in Onthophagines

4.1 Introduction

4.2 Sperm competition theory

4.3 Evolution of ejaculate expenditure in the genus Onthophagus

4.4 Evolutionary consequences of variation in ejaculate expenditure

4.5 Theoretical models of female choice

4.6 Quantitative genetics of ejaculate traits

4.7 Empirical evidence for adaptive cryptic female choice in Onthophagus taurus

4.8 Conclusions and future directions

4.9 Dedication and acknowledgement

5 Olfactory Ecology

5.1 Introduction

5.2 Orientation to dung and other resources

5.3 Olfactory cues used in mate attraction and mate recognition

5.3.1 Morphology of pheromone-producing and -dispersing structures

5.3.2 Pheromone-dispersing behaviour

5.4 Chemical composition of Kheper pheromones

5.4.1 Electroantennographic detection

5.4.2 Comparison of the responses of beetle species to attractant compounds

5.4.3 The pheromone-disseminating carrier material

5.5 Kairomones

5.6 Defensive secretions

5.7 Conclusions and future directions

6 Explaining Phenotypic Diversity: The Conditional Strategy and Threshold Trait Expression

6.1 Introduction

6.2 The environmental threshold model

6.2.1 Does the development of a horn dimorphism in male dung beetles occur in a manner consistent with the assumptions of the ET model?

6.3 Applying the threshold model

6.3.1 Predicting the mean switchpoint of a population

6.3.2 Estimating the selection on thresholds using the ET model

6.3.3 Estimating selection under positive allometry

6.4 Future directions

7 Evolution and Development: Onthophagus Beetles and the Evolutionary Developmental Genetics of Innovation, Allometry and Plasticity

7.1 Introduction

7.2 Evo-devo and eco-devo – a brief introduction

7.3 Onthophagus beetles as an emerging model system in evo-devo and eco-devo

7.4 The origin and diversification of novel traits

7.4.1 Dung beetle horns as novel traits

7.4.2 How horns develop

7.4.3 The developmental genetics of horn growth

7.4.5 The origin of adult thoracic horns through exaptation

7.5 The regulation and evolution of scaling

7.5.1 Onthophagine scaling relationships: the roles of nutrition and hormones

7.5.2 Onthophagine scaling relationships: the role of trade-offs during development and evolution

7.5.3 Onthophagine scaling relationships: developmental decoupling versus common developmental programme

7.5.4 Onthophagine scaling relationships: the developmental genetics of size and shape

7.6 The development, evolution, and consequences of phenotypic plasticity

7.6.1 Developmental mechanisms and the evolutionary consequences of plasticity

7.7 Conclusion

8 The Evolution of Parental Care in the Onthophagine Dung Beetles

8.1 Introduction

8.2 Parental care theory

8.2.1 A conventional view of parental care theory

8.2.2 More recent developments in parental care theory

8.3 Testing parental care theory using onthophagine dung beetles

8.3.1 Parental care in onthophagine dung beetles

8.3.2 The costs and benefits of parental care in onthophagine dung beetles

8.3.3 Behavioural dynamics of the sexes during biparental care

8.3.4 Confidence of paternity and paternal care

8.3.5 Do parents optimize the care they provide?

8.3.6 Evolutionary quantitative genetics of parental care

8.4 Conclusions and future directions

9 The Visual Ecology of Dung Beetles

9.1 Introduction

9.2 Insect eye structure

9.2.1 The apposition eye

9.2.2 The superposition eye

9.3 Eye limitations

9.4 Dung beetle vision

9.4.1 Dim light vision

9.4.2 The tapetum and enlarged rhabdoms

9.4.3 The canthus

9.5 Visual ecology of flight activity

9.5.1 Diel flight activity

9.5.2 Crepuscular flight activity

9.5.3 Endothermy and vision

9.5.4 Body size and flight activity

9.6 Sexual selection and eyes

9.7 Ball-rolling

9.7.1 Orientation by ball-rolling beetles

9.7.2 The polarization compass

9.7.3 Polarization vision

9.7.4 Polarization vision in dim light

9.8 Conclusions

10 The Ecological Implications of Physiological Diversity in Dung Beetles

10.1 Introduction

10.2 Thermoregulation

10.3 Thermal tolerance

10.4 Water balance

10.5 Gas exchange and metabolic rate

10.6 Conclusion and prospectus

11 Dung Beetle Populations: Structure and Consequences

11.1 Introduction

11.2 Study systems

11.2.1 The Finnish cow pat

11.2.2 The Malagasy lemur pellet

11.3 Range size

11.4 Habitat and resource selection

11.5 Dung beetle movement

11.6 The genetic structure of dung beetle populations

11.7 Consequences: spatial population structures and responses to habitat loss

11.8 Perspectives

12 Biological Control: Ecosystem Functions Provided by Dung Beetles

12.1 Introduction

12.2 Functions of dung beetles in ecosystems

12.2.1 Dung burial and nutrient cycling

12.2.2 Control of dung-breeding flies

12.2.3 Control of parasites

12.3 Dung beetles in pasture habitats

12.4 Seasonal occurrence and abundance of native dung beetles in Australia

12.5 Distribution and seasonal occurrence of introduced dung beetles in Australia

12.6 Long-term studies of establishment and abundance

12.6.1 Summer rainfall climate area of Queensland

12.6.2 Mediterranean climate area of south Western Australia

12.6.3 Long-term population trends

12.7 Competitive exclusion

12.8 Optimizing the benefits of biological control

13 Dung Beetles as a Candidate Study Taxon in Applied Biodiversity Conservation Research

13.1 Introduction

13.2 Satisfying data needs to inform conservation practice

13.3 The role of dung beetles in applied biodiversity research in human-modified landscapes

13.3.1 Dung beetles as a viable candidate for biodiversity research

13.3.2 Dung beetles as reliable indicators of environmental change

13.3.3 Interpreting disturbance response patterns: application of a trait-based framework for ecological research

13.3.4 Dung beetles as ecological disturbance indicator taxa: applied examples

13.4 Dung beetle conservation

13.5 Some ways forward

References

Subject Index

Taxonomic Index