Limits...
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.

Show MeSH
Photograph of a baskingJunonia almana, from which the models were derived.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig4: Photograph of a baskingJunonia almana, from which the models were derived.

Mentions: Butterfly models were digitally manipulated from a photograph of a real specimen of J. almana in its resting position (Figure 4), using GIMP v 2.8 [60] and were printed on matte paper of 60 × 35 mm dimensions, matching the natural wingspan of J. almana [61]. In each trial a bird was presented with a choice between two paper models glued onto a beige cardboard of dimensions 250 × 100 mm with a distance of 190 mm between the centres of the butterfly models (Additional file 2: Figure S1 ii.). The patterns along the wing margins were erased, and the wings’ colour was modified to a uniform yellow-ochre, matching the natural dominant wing colour. The shape, size and arrangement of eyespots were manipulated for a series of experiments described in the next section. The birds had been habituated to feed on broken corn, and we therefore decided to use the same in the trials instead of mealworms or other food. Broken corn were placed as a trail to lead the naïve chicken towards the two choices, ending at the cardboard rectangle with the glued paper butterflies. Three broken corn pieces were placed on the mid-body of each model, and a peck on one of the pieces was considered to be an attack.Figure 4


What makes eyespots intimidating-the importance of pairedness.

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

Photograph of a baskingJunonia almana, from which the models were derived.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig4: Photograph of a baskingJunonia almana, from which the models were derived.
Mentions: Butterfly models were digitally manipulated from a photograph of a real specimen of J. almana in its resting position (Figure 4), using GIMP v 2.8 [60] and were printed on matte paper of 60 × 35 mm dimensions, matching the natural wingspan of J. almana [61]. In each trial a bird was presented with a choice between two paper models glued onto a beige cardboard of dimensions 250 × 100 mm with a distance of 190 mm between the centres of the butterfly models (Additional file 2: Figure S1 ii.). The patterns along the wing margins were erased, and the wings’ colour was modified to a uniform yellow-ochre, matching the natural dominant wing colour. The shape, size and arrangement of eyespots were manipulated for a series of experiments described in the next section. The birds had been habituated to feed on broken corn, and we therefore decided to use the same in the trials instead of mealworms or other food. Broken corn were placed as a trail to lead the naïve chicken towards the two choices, ending at the cardboard rectangle with the glued paper butterflies. Three broken corn pieces were placed on the mid-body of each model, and a peck on one of the pieces was considered to be an attack.Figure 4

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