Conspicuous visual signals do not coevolve with increased body size in marine sea slugs

Cheney, K. L., Cortesi, F., How, M. J., Wilson, N. G., Blomberg, S. P., Winters, A. E., Umanzor, S. and Marshall, N. J. (2014) Conspicuous visual signals do not coevolve with increased body size in marine sea slugs. Journal of Evolutionary Biology, 27 4: 676-687. doi:10.1111/jeb.12348

Author Cheney, K. L.
Cortesi, F.
How, M. J.
Wilson, N. G.
Blomberg, S. P.
Winters, A. E.
Umanzor, S.
Marshall, N. J.
Title Conspicuous visual signals do not coevolve with increased body size in marine sea slugs
Journal name Journal of Evolutionary Biology   Check publisher's open access policy
ISSN 1010-061X
Publication date 2014-01-01
Year available 2014
Sub-type Article (original research)
DOI 10.1111/jeb.12348
Open Access Status Not yet assessed
Volume 27
Issue 4
Start page 676
End page 687
Total pages 12
Place of publication Chichester, West Sussex, United Kingdom
Publisher Blackwell Publishing Ltd
Language eng
Subject 1105 Dentistry
Abstract Many taxa use conspicuous colouration to attract mates, signal chemical defences (aposematism) or for thermoregulation. Conspicuousness is a key feature of aposematic signals, and experimental evidence suggests that predators avoid conspicuous prey more readily when they exhibit larger body size and/or pattern elements. Aposematic prey species may therefore evolve a larger body size due to predatory selection pressures, or alternatively, larger prey species may be more likely to evolve aposematic colouration. Therefore, a positive correlation between conspicuousness and body size should exist. Here, we investigated whether there was a phylogenetic correlation between the conspicuousness of animal patterns and body size using an intriguing, understudied model system to examine questions on the evolution of animal signals, namely nudibranchs (opisthobranch molluscs). We also used new ways to compare animal patterns quantitatively with their background habitat in terms of intensity variance and spatial frequency power spectra. In studies of aposematism, conspicuousness is usually quantified using the spectral contrast of animal colour patches against its background; however, other components of visual signals, such as pattern, luminance and spectral sensitivities of potential observers, are largely ignored. Contrary to our prediction, we found that the conspicuousness of body patterns in over 70 nudibranch species decreased as body size increased, indicating that crypsis was not limited to a smaller body size. Therefore, alternative selective pressures on body size and development of colour patterns, other than those inflicted by visual hunting predators, may act more strongly on the evolution of aposematism in nudibranch molluscs.
Keyword Animal patterns
Image statistics
Spectral contrast
Visual signalling
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Queensland Brain Institute Publications
Official 2015 Collection
School of Biological Sciences Publications
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