Investigating the behavioural consequences of evolutionary signal loss in the context of a naturalistic environment
Abstract
The evolutionary loss of sexual traits is thought to be common, but empirical examples of it
occurring are rare. In this thesis, I investigate social and other behavioural factors that might
facilitate signal loss. Specifically, I took an empirical approach to evaluate the ways in which
the loss of a long-range acoustic signal, song, alters the mating dynamics and social behaviours
of individuals in affected populations. This confronts a methodological challenge in behavioural
research – the difficulty of observing and measuring behaviours from within a natural context - a context that includes the physical and social environmental conditions in which they evolved.
To overcome this challenge and to study the consequences of sexual signal loss, I developed a
novel tracking system to monitor, in a laboratory setting that mimicked field-like conditions,
the behaviour of a cricket species in which some males have lost the ability to sing. In
populations of the Hawaiian field cricket, Teleogryllus oceanicus, silent ‘flatwing’ males carry
mutations that remove key wing structures, eliminating acoustic signalling and affording
protection against an acoustically-orientating parasitoid fly (Ormia ochracea). This also
removes their ability to attract females via song. Despite this, largely silent populations persist
in the wild. Using the developed tracking system to monitor groups of individually-tagged
crickets, I show how behavioural plasticity of both males and females might accommodate the
disappearance of song and mitigate negative effects on reproductive fitness. This appears to
be achieved by increased movement activity and changes to key social interaction dynamics.
My results highlight the flexible and potentially compensatory nature of animal behaviour in
facilitating rapid evolutionary change.
Type
Thesis, PhD Doctor of Philosophy
Rights
Embargo Date: 2022-02-19
Embargo Reason: Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 19th February 2022
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