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Is female preference for large sexual ornaments due to a bias to escape predation risk?

Zhu Z, Kim TW, Choe JC - BMC Evol. Biol. (2012)

Bottom Line: Females had a directional preference for males with bigger semidomes within normal variation.When threatened by an avian mock predator, females preferentially approached burrows with full-sized semidomes regardless of reproductive cycles (i.e. reproductive periods and non-reproductive periods).Results indicate that selection for the size of courtship structures in U. lactea may have an origin in the function to reduce predation risk, but that the preference for males with structures may have evolved by female choice, independent of predation pressure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Behavior and Ecology, Division of EcoSicence, Ewha Womans University, Seoul 120-750, South Korea.

ABSTRACT

Background: A female preference for intense sexual visual signals is widespread in animals. Although the preferences for a signal per se and for the intensity of the signal were often regarded to have the identical origin, no study has demonstrated if this is true. It was suggested that the female fiddler crabs prefer males with courtship structures because of direct benefit to escape predation. Here we tested if female preference for both components (i.e. presence and size) of the courtship structure in Uca lactea is from the sensory bias to escape predation. If both components have the identical origin, females should show the same response to different-sized courtship structures regardless of predation risk.

Results: First, we observed responses of mate-searching female U. lactea to courting males with full-sized, half-sized and no semidomes which were experimentally manipulated. Females had a directional preference for males with bigger semidomes within normal variation. Thereafter, we tested the effect of predation risk on the female bias in the non-courtship context. When threatened by an avian mock predator, females preferentially approached burrows with full-sized semidomes regardless of reproductive cycles (i.e. reproductive periods and non-reproductive periods). When the predator cue was absent, however, females preferred burrows with semidomes without discriminating structure size during reproductive periods but did not show any bias during non-reproductive periods.

Conclusions: Results indicate that selection for the size of courtship structures in U. lactea may have an origin in the function to reduce predation risk, but that the preference for males with structures may have evolved by female choice, independent of predation pressure.

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Visiting frequency by females to artificial burrows with full-sized, half-sized or without semidome under (a) predator-present condition and (b) predator-absent condition in the arena test.
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Figure 1: Visiting frequency by females to artificial burrows with full-sized, half-sized or without semidome under (a) predator-present condition and (b) predator-absent condition in the arena test.

Mentions: Under high predation risk, female choices did not differ significantly between reproductive periods and non-reproductive periods (X2 = 0.033, d.f. = 2, p = 0.983). Under low predation risk, however, there was significant difference between two periods (X2 = 9.013, d.f. = 2, p = 0.011). More females moved to burrows with full-sized semidomes than to burrows with half-sized semidomes or without semdiomes in the presence of a mock predator (X2 = 61.659, d.f. = 2, p < 0.001, Figure 1a). In the absence of a mock predator, however, females showed different orientation biases varying with the reproductive cycle (Figure 1b): females during reproductive periods preferred to move to burrows with semidomes rather than to burrows without semidomes (X2 = 8.665, d.f. = 1, p = 0.003), but did not discriminate between the sizes of semidomes (X2 = 0.385, d.f. = 1, p = 0.535); during non-reproductive periods, females did not show any orientation bias to different semidome treatments (X2 = 1.316, d.f. = 2, p = 0.518).


Is female preference for large sexual ornaments due to a bias to escape predation risk?

Zhu Z, Kim TW, Choe JC - BMC Evol. Biol. (2012)

Visiting frequency by females to artificial burrows with full-sized, half-sized or without semidome under (a) predator-present condition and (b) predator-absent condition in the arena test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3313857&req=5

Figure 1: Visiting frequency by females to artificial burrows with full-sized, half-sized or without semidome under (a) predator-present condition and (b) predator-absent condition in the arena test.
Mentions: Under high predation risk, female choices did not differ significantly between reproductive periods and non-reproductive periods (X2 = 0.033, d.f. = 2, p = 0.983). Under low predation risk, however, there was significant difference between two periods (X2 = 9.013, d.f. = 2, p = 0.011). More females moved to burrows with full-sized semidomes than to burrows with half-sized semidomes or without semdiomes in the presence of a mock predator (X2 = 61.659, d.f. = 2, p < 0.001, Figure 1a). In the absence of a mock predator, however, females showed different orientation biases varying with the reproductive cycle (Figure 1b): females during reproductive periods preferred to move to burrows with semidomes rather than to burrows without semidomes (X2 = 8.665, d.f. = 1, p = 0.003), but did not discriminate between the sizes of semidomes (X2 = 0.385, d.f. = 1, p = 0.535); during non-reproductive periods, females did not show any orientation bias to different semidome treatments (X2 = 1.316, d.f. = 2, p = 0.518).

Bottom Line: Females had a directional preference for males with bigger semidomes within normal variation.When threatened by an avian mock predator, females preferentially approached burrows with full-sized semidomes regardless of reproductive cycles (i.e. reproductive periods and non-reproductive periods).Results indicate that selection for the size of courtship structures in U. lactea may have an origin in the function to reduce predation risk, but that the preference for males with structures may have evolved by female choice, independent of predation pressure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Behavior and Ecology, Division of EcoSicence, Ewha Womans University, Seoul 120-750, South Korea.

ABSTRACT

Background: A female preference for intense sexual visual signals is widespread in animals. Although the preferences for a signal per se and for the intensity of the signal were often regarded to have the identical origin, no study has demonstrated if this is true. It was suggested that the female fiddler crabs prefer males with courtship structures because of direct benefit to escape predation. Here we tested if female preference for both components (i.e. presence and size) of the courtship structure in Uca lactea is from the sensory bias to escape predation. If both components have the identical origin, females should show the same response to different-sized courtship structures regardless of predation risk.

Results: First, we observed responses of mate-searching female U. lactea to courting males with full-sized, half-sized and no semidomes which were experimentally manipulated. Females had a directional preference for males with bigger semidomes within normal variation. Thereafter, we tested the effect of predation risk on the female bias in the non-courtship context. When threatened by an avian mock predator, females preferentially approached burrows with full-sized semidomes regardless of reproductive cycles (i.e. reproductive periods and non-reproductive periods). When the predator cue was absent, however, females preferred burrows with semidomes without discriminating structure size during reproductive periods but did not show any bias during non-reproductive periods.

Conclusions: Results indicate that selection for the size of courtship structures in U. lactea may have an origin in the function to reduce predation risk, but that the preference for males with structures may have evolved by female choice, independent of predation pressure.

Show MeSH
Related in: MedlinePlus