Causes of signal mimicry and its consequences for optimal investment in prey defences
Lead Research Organisation:
University of Liverpool
Department Name: Sch of Biological Sciences
Abstract
Prey defences are key components in the structuring of ecological communities. Many prey protect themselves from predators by investment in repellent 'secondary' defences (toxins, stings, sharp spines etc.). Many such prey share conspicuous warning signals to deter predation. Despite the importance of secondary defences and of signal mimicry to the understanding of the structure of different ecosystems: (i) there is currently almost no theoretical information about the evolutionary optimisation of such defences; (ii) the causal basis of signal mimicry is uncertain and controversial and (iii) there are no studies of the coevolutionary relationship between stable signal mimicry and optimal secondary defences. We argue that the nature and benefits that accrue from variations in the abundance of defended prey within a locality (and indeed the benefits that accrue from signal mimicry between them) has profound implications for the optimal investment that each individual should make in its secondary defence. If prey are well protected by the presence of other defended forms and by mimicry, then it may be optimal for individuals to decrease their investment in their defences. Conversely, if prey defences are constrained, then signal mimicry may become evolutionarily advantageous, even if it incurs some costs (deformation of organs, reduced locomotor efficiency). Hence the evolution of mimicry and secondary defences are bound up in a complex coevolutionary manner that can not be elucidated by verbal reasoning alone. Thus, we (Speed & Ruxton 2005) have developed a novel theoretical system which models evolutionary stable investment in defence (and simultaneously in other traits such as costly warning signals and mimicry). This allows evaluation of the coevolutionary relationship between defensive traits and though presently simple in form, can easily be developed to provide highly informative predictions. We currently lack basic knowledge about the causal nature of signal mimicry, of the importance of defensive mutualisms and of the controls of key aspects of predator behaviour. Without such knowledge, the theoretical foundations of our understanding of optimal prey defences will remain speculative. We propose therefore to employ an experienced PDRA to help refine and perform experiments that will test the plausibility and relative importance of alternative explanations for signal mimicry. These experiments will be hosted by our project partner, Prof. Johanna Mappes, (University of Jyvaskyla, Finland), who will provide very considerable empirical expertise and the use of specially designed behaviour laboratories. The PDRA will also run behaviour experiments in the UK, establishing the characteristics of behavioural parameters that are key to the construction of predictive, nonspeculative theoretical models. The endpoint of the project will see (i) a clarification about the causal nature of signal mimicry; (ii) genuinely new insights into the evolutionary relationships between warning signals, signal mimicry and the evolution of secondary defences.
People |
ORCID iD |
Michael Speed (Principal Investigator) |
Publications
Blount J
(2012)
How the ladybird got its spots: effects of resource limitation on the honesty of aposematic signals
in Functional Ecology
Blount JD
(2009)
Warning displays may function as honest signals of toxicity.
in Proceedings. Biological sciences
Blount JD
(2023)
The price of defence: toxins, visual signals and oxidative state in an aposematic butterfly.
in Proceedings. Biological sciences
Rowland H
(2010)
A tale of 2 signals: signal mimicry between aposematic species enhances predator avoidance learning
in Behavioral Ecology
Rowland HM
(2010)
When more is less: the fitness consequences of predators attacking more unpalatable prey when more are presented.
in Biology letters
Rowland HM
(2010)
Mimicry between unequally defended prey can be parasitic: evidence for quasi-Batesian mimicry.
in Ecology letters
Saxton T
(2009)
Trade-offs between markers of absolute and relative quality in human facial preferences
in Behavioral Ecology
Speed MP
(2010)
Imperfect Batesian mimicry and the conspicuousness costs of mimetic resemblance.
in The American naturalist
Description | This grant explored the evolution of defensive mimicry - one of the most important case studies in natural selection. We re-examined its causal basis and found strong support for new theoretical mechanisms by which mimicry evolves. This grant completed some time ago. Outputs have been classed as satisfactory by NERC. |
Exploitation Route | Part of the grant was to examine the role that nutritional state played in the decision making of predators. This may be (albeit tangentially) of use in animal feed production. |
Sectors | Agriculture Food and Drink |
Description | This grant was awarded before NERC introducted Impact plans etc. Hence there were no plans not budget for this. |
First Year Of Impact | 2009 |