Macquarie University
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Causes and consequences of colour variation in Tectocoris diophthalmus (Heteroptera: Scutelleridae)

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posted on 2022-03-28, 17:49 authored by Scott Adam Fabricant
Aposematism, the pairing of conspicuous signals with unpalatability in potential prey, is suggested by theory and empirical evidence to be under frequency-based selection for uniformity and maximal conspicuousness. However, this is often not the case in nature, and variation in warning colouration is not uncommon. Studies have generally looked at this paradox from one of two perspectives: the sender's physiological trade-offs, or the receiver's (predators) visual physiology and psychology. Here we consider both perspectives simultaneously, using the highly variable Hibiscus Harlequin Bug, Tectocoris diophthalmus (Heteroptera: Scutelleridae). This shieldback stinkbug has an orange base colour and highly reflectant blue-green iridescent patches that range in size from absent to entirely covering the dorsal surface. First, I critically examined the role of arthropod taxa in aposematism studies, and highlight the valuable contributions to the field further experimentation can make. Then I examined the sender's colour production mechanisms, to identify sources of variation and potential physiological trade-offs. Next I surveyed intra and inter-population variation, to model and empirically test the influence of environmental factors on patterns of variation. Then I tested sensitivity to chemical defences of multiple ecologically-relevant predators, and assayed two disparate taxa (a passerine bird and praying mantid) for their behavioural responses to colour variation, to determine how they may be selecting for or against maintaining variation. In conclusion, colouration in T. diophthalmus is a complex, phenotypically plastic trait under multiple selective drivers to create and maintain variation. By looking at the perspective of both sender and multiple receivers, we now have a more complete, cohesive, and holistic understanding of intraspecific variation of warning colouration in this species.


Table of Contents

Introduction -- 1. The unique insights to be gained in using arthropod predators to study aposematism -- 2. Mechanisms of colour production in a highly variable shieldback stinkbug, Tectocoris diophthalmus (Heteroptera: Scutelleridae) and why it matters -- 3. Is the Hibiscus Harlequin Bug aposematic? The importance of testing multiple predators -- 4. Ecological factors shaping phenotypically plastic iridescent coloration in Tectocoris diophthalmus (Heteroptera: Scutelleridae) -- 5. Scared by shiny? The value of iridescence in aposematic signaling of Hibiscus Harlequin Bugs (Tectocoris diophthalmus) -- 6. Hidden in plain orange: aposematic coloration is cryptic to a colorblind insect predator -- Conclusions -- Appendices


Includes bibliographical references "August 2013 Thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy"

Awarding Institution

Macquarie University

Degree Type

Thesis PhD


PhD, Macquarie University, Faculty of Science, Department of Biological Sciences

Department, Centre or School

Department of Biological Sciences

Year of Award


Principal Supervisor

Mariella Herberstein


Copyright Scott Adam Fabricant 2013. Copyright disclaimer:




1 online resource (v, 251 pages) illustrations (some colour)

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