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What makes eyespots intimidating-the importance of pairedness.

Mukherjee R, Kodandaramaiah U - BMC Evol. Biol. (2015)

Bottom Line: However, contrary to previous, outdoor experiments, we found that the total area of eyespots did not affect their effectiveness.Non-eye-like, fan shaped patterns derived from eyespots were found to be just as effective as eye-like circular patterns.Furthermore, we did not find a significant effect of symmetry of patterns, again in discordance with previous work.

View Article: PubMed Central - PubMed

Affiliation: School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, CET campus, Trivandrum, 695016, India. ritwika@iisertvm.ac.in.

ABSTRACT

Background: Many butterflies possess striking structures called eyespots on their wings, and several studies have sought to understand the selective forces that have shaped their evolution. Work over the last decade has shown that a major function of eyespots is their ability to reduce predation by being intimidating to attacking predators. Two competing hypotheses seek to explain the cause of intimidation, one suggesting 'eye-mimicry' and the other their 'conspicuousness' as the reason. There is an on-going debate about which of these better explains the effectiveness of eyespots against predation. We undertook a series of indoor experiments to understand the relative importance of conspicuousness and eye-mimicry, and therefore how predator perception may have influenced the evolution of eyespots. We conducted choice tests where artificial paper models mimicking Junonia almana butterflies were presented to chickens and their preference of attack recorded.

Results: We first established that birds avoided models with a pair of eyespots. However, contrary to previous, outdoor experiments, we found that the total area of eyespots did not affect their effectiveness. Non-eye-like, fan shaped patterns derived from eyespots were found to be just as effective as eye-like circular patterns. Furthermore, we did not find a significant effect of symmetry of patterns, again in discordance with previous work. However, across all experiments, models with a pair of patterns, symmetric or asymmetric, eyelike or non-eye-like, suffered from fewer attacks compared with other models.

Conclusions: The study highlights the importance of pairedness of eyespots, and supports the hypothesis that two is a biologically significant number that is important in prey-predator signalling. We discuss the implications of our results for the understanding of eyespot evolution.

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Summary of the preferences for first attacks of birds in all the experiments described previously. ' > ' and ' < ' symbols indicates the significant preference and ' = ' indicates no difference.
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Fig3: Summary of the preferences for first attacks of birds in all the experiments described previously. ' > ' and ' < ' symbols indicates the significant preference and ' = ' indicates no difference.

Mentions: In the series of experiments employing a total of 603 birds, we have tested specific predictions of the eye-mimicry and conspicuousness hypotheses, two competing hypotheses that have a bearing on our understanding of how eyespots may have evolved in nature. The data do not unequivocally favor either hypothesis. Figure 3 summarizes results from all experiments. However, the results of our study question the generality of existing paradigms and augment our understanding of what properties make eyespots effective against predation.Figure 3


What makes eyespots intimidating-the importance of pairedness.

Mukherjee R, Kodandaramaiah U - BMC Evol. Biol. (2015)

Summary of the preferences for first attacks of birds in all the experiments described previously. ' > ' and ' < ' symbols indicates the significant preference and ' = ' indicates no difference.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4374370&req=5

Fig3: Summary of the preferences for first attacks of birds in all the experiments described previously. ' > ' and ' < ' symbols indicates the significant preference and ' = ' indicates no difference.
Mentions: In the series of experiments employing a total of 603 birds, we have tested specific predictions of the eye-mimicry and conspicuousness hypotheses, two competing hypotheses that have a bearing on our understanding of how eyespots may have evolved in nature. The data do not unequivocally favor either hypothesis. Figure 3 summarizes results from all experiments. However, the results of our study question the generality of existing paradigms and augment our understanding of what properties make eyespots effective against predation.Figure 3

Bottom Line: However, contrary to previous, outdoor experiments, we found that the total area of eyespots did not affect their effectiveness.Non-eye-like, fan shaped patterns derived from eyespots were found to be just as effective as eye-like circular patterns.Furthermore, we did not find a significant effect of symmetry of patterns, again in discordance with previous work.

View Article: PubMed Central - PubMed

Affiliation: School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, CET campus, Trivandrum, 695016, India. ritwika@iisertvm.ac.in.

ABSTRACT

Background: Many butterflies possess striking structures called eyespots on their wings, and several studies have sought to understand the selective forces that have shaped their evolution. Work over the last decade has shown that a major function of eyespots is their ability to reduce predation by being intimidating to attacking predators. Two competing hypotheses seek to explain the cause of intimidation, one suggesting 'eye-mimicry' and the other their 'conspicuousness' as the reason. There is an on-going debate about which of these better explains the effectiveness of eyespots against predation. We undertook a series of indoor experiments to understand the relative importance of conspicuousness and eye-mimicry, and therefore how predator perception may have influenced the evolution of eyespots. We conducted choice tests where artificial paper models mimicking Junonia almana butterflies were presented to chickens and their preference of attack recorded.

Results: We first established that birds avoided models with a pair of eyespots. However, contrary to previous, outdoor experiments, we found that the total area of eyespots did not affect their effectiveness. Non-eye-like, fan shaped patterns derived from eyespots were found to be just as effective as eye-like circular patterns. Furthermore, we did not find a significant effect of symmetry of patterns, again in discordance with previous work. However, across all experiments, models with a pair of patterns, symmetric or asymmetric, eyelike or non-eye-like, suffered from fewer attacks compared with other models.

Conclusions: The study highlights the importance of pairedness of eyespots, and supports the hypothesis that two is a biologically significant number that is important in prey-predator signalling. We discuss the implications of our results for the understanding of eyespot evolution.

Show MeSH