Evolution; international journal of organic evolution, Jan 19, 2015
Predation exerts strong selection on mimetic butterfly wing colour patterns, which also serve oth... more Predation exerts strong selection on mimetic butterfly wing colour patterns, which also serve other functions such as sexual selection. Therefore, specific selection pressures may affect the sexes and signal components differentially. We tested three predictions about the evolution of mimetic resemblance by comparing wing colouration of aposematic butterflies and their Batesian mimics: (a) females gain greater mimetic advantage than males and therefore are better mimics, (b) due to intersexual genetic correlations, sexually monomorphic mimics are better mimics than female-limited mimics, and (c) mimetic resemblance is better on the dorsal wing surface which is visible to predators in flight. Using a physiological model of avian colour vision, we quantified mimetic resemblance from predators' perspective, which showed that female butterflies were better mimics than males. Mimetic resemblance in female-limited mimics was comparable to that in sexually monomorphic mimics, suggestin...
No animals are known to possess both ultraviolet (UV) reflectance and fluorescence that are sex-s... more No animals are known to possess both ultraviolet (UV) reflectance and fluorescence that are sex-specific. We provide evidence for this separation in the jumping spider Cosmophasis umbratica, which has UV reflectance and UV-induced green fluorescence restricted to males and females, respectively. During courtship, many of the studied pairs failed to show typical display posturing when UV light was blocked. Occluding the UV component of sunlight to only one of each pair also caused atypical behavior: Females showed no interest in non‐UV-reflective courting males, and males either ignored or were lackluster in courting nonfluorescing females. These results demonstrate the importance of both sex-specific hues as sexual signals for effective intraspecific communication.
Proceedings of the Royal Society B: Biological Sciences, 2007
Recent studies have shown for birds that females sometimes choose mates on the basis of condition... more Recent studies have shown for birds that females sometimes choose mates on the basis of condition-dependent variation in ultraviolet (UV, less than 400 nm) ornamentation, but there have been few comparable studies on invertebrates. Yet many invertebrates have UV structural coloration. Here, we investigate Cosmophasis umbratica , a jumping spider (Araneae: Salticidae) that has sexually dimorphic UV-iridescent ornamentation, and we provide evidence that male UV coloration is condition dependent in this species. Spectral-reflection patterns change with male age and prior feeding history. The position of the UV band (i.e. UV hue) of the carapaces of younger (field-collected as subadults and matured as adults in laboratory) males shifted, relative to older (field-collected as adults) males, significantly towards longer wavelengths. Food deprivation significantly decreased the spectral intensity of the abdomen, but not the carapace. Questions concerning the mechanisms by which UV ornament...
Animal colour signals used in intraspecies communications can generally be attributed to a compos... more Animal colour signals used in intraspecies communications can generally be attributed to a composite effect of structural and pigmentary colours. Notably, the functional role of iridescent coloration that is 'purely' structural (i.e., absence of pigments) is poorly understood. Recent studies reveal that iridescent colorations can reliably indicate individual quality, but evidence of iridescence as a pure structural coloration indicative of male quality during contests and relating to an individual's resource-holding potential (RHP) is lacking. In age-and size-controlled pairwise male-male contests that escalate from visual displays of aggression to more costly physical fights, we demonstrate that the ultraviolet-green iridescence of Cosmophasis umbratica predicts individual persistence and relates to RHP. Contest initiating males exhibited significantly narrower carapace band separation (i.e., relative spectral positions of UV and green hues) than non-initiators. Asymmetries in carapace and abdomen brightness influenced overall contest duration and escalation. As losers retreated upon having reached their own persistence limits in contests that escalated to physical fights, losers with narrower carapace band separation were significantly more persistence. We propose that the carapace UV-green iridescence of C. umbratica predicts individual persistence and is indicative of a male's RHP. As the observed UV-green hues of C. umbratica are 'pure' optical products of a multilayer reflector system, we suggest that intrasexual variations in the optical properties of the scales' chitinair-chitin microstructures are responsible for the observed differences in carapace band separations.
Journal of Experimental Marine Biology and Ecology, 2011
Bright colours are a key visual signal in many animal communication systems. Here we examine the ... more Bright colours are a key visual signal in many animal communication systems. Here we examine the function of the blue-green facial bands found in two species of mangrove crabs, Perisesarma eumolpe (De Man) and P. indiarum (Tweedie). Food (mangrove leaves) ...
... such as shuttling, dropping, and pumping (A. argen-tata: Robinson & Robinson, 197... more ... such as shuttling, dropping, and pumping (A. argen-tata: Robinson & Robinson, 1970; A. appensa: Jackson et al., 1993; re-view: Cloudsley-Thompson, 1995; Rayor, 1996; Blackledge & Pickett, 2000; Blackledge & Wenzel, 2001). However, unlike many other orb-weaving spi ...
ABSTRACT Highlights ► We blocked reflections from Argiope versicolor web decorations at different... more ABSTRACT Highlights ► We blocked reflections from Argiope versicolor web decorations at different wavelengths. ► Only blocking UV reflections reduced number of Portia approaching webs. ► Thus UV is more important than other wavelengths for Portia to locate Argiope.
Stabilimenta, the conspicuous, ultraviolet (UV)-reflecting, white silk structures around the hub ... more Stabilimenta, the conspicuous, ultraviolet (UV)-reflecting, white silk structures around the hub of orb webs, are thought to increase a spider's foraging success by attracting prey (prey attraction hypothesis). No studies, however, have yet investigated the function of nonlinear and noncruciform stabilimenta and the stabilimenta of juvenile spiders. We examined whether the discoid stabilimenta spun by juvenile Argiope versicolor, an orb-spinning spider, function to attract prey. When we measured the UV reflectance of the web silks of A. versicolor juveniles, we found that the discoid stabilimentum silk, but not spiral silk or radial silk or the joint where the two types of silk met, reflected UV light. We then carried out two series of choice experiments in the laboratory to determine whether the webs with discoid stabilimenta attract more fruit flies than undecorated webs when UVC white light (300-700 nm) is present. We also examined whether the discoid stabilimenta still attract insects when the UV section of the spectrum (300-400 nm) is eliminated (UVÿ). Webs with discoid stabilimenta attracted more fruit flies than the webs without stabilimenta in UVC white light. However, in UVÿ light, fewer fruit flies flew to the webs, even when they were decorated with discoid stabilimenta. In a field experiment, significantly more insects were intercepted by webs with discoid stabilimenta than by webs without stabilimenta. We suggest that the discoid stabilimenta of A. versicolor juveniles act as a visual signal that attracts insects, supporting the prey attraction hypothesis.
Evolution; international journal of organic evolution, Jan 19, 2015
Predation exerts strong selection on mimetic butterfly wing colour patterns, which also serve oth... more Predation exerts strong selection on mimetic butterfly wing colour patterns, which also serve other functions such as sexual selection. Therefore, specific selection pressures may affect the sexes and signal components differentially. We tested three predictions about the evolution of mimetic resemblance by comparing wing colouration of aposematic butterflies and their Batesian mimics: (a) females gain greater mimetic advantage than males and therefore are better mimics, (b) due to intersexual genetic correlations, sexually monomorphic mimics are better mimics than female-limited mimics, and (c) mimetic resemblance is better on the dorsal wing surface which is visible to predators in flight. Using a physiological model of avian colour vision, we quantified mimetic resemblance from predators' perspective, which showed that female butterflies were better mimics than males. Mimetic resemblance in female-limited mimics was comparable to that in sexually monomorphic mimics, suggestin...
No animals are known to possess both ultraviolet (UV) reflectance and fluorescence that are sex-s... more No animals are known to possess both ultraviolet (UV) reflectance and fluorescence that are sex-specific. We provide evidence for this separation in the jumping spider Cosmophasis umbratica, which has UV reflectance and UV-induced green fluorescence restricted to males and females, respectively. During courtship, many of the studied pairs failed to show typical display posturing when UV light was blocked. Occluding the UV component of sunlight to only one of each pair also caused atypical behavior: Females showed no interest in non‐UV-reflective courting males, and males either ignored or were lackluster in courting nonfluorescing females. These results demonstrate the importance of both sex-specific hues as sexual signals for effective intraspecific communication.
Proceedings of the Royal Society B: Biological Sciences, 2007
Recent studies have shown for birds that females sometimes choose mates on the basis of condition... more Recent studies have shown for birds that females sometimes choose mates on the basis of condition-dependent variation in ultraviolet (UV, less than 400 nm) ornamentation, but there have been few comparable studies on invertebrates. Yet many invertebrates have UV structural coloration. Here, we investigate Cosmophasis umbratica , a jumping spider (Araneae: Salticidae) that has sexually dimorphic UV-iridescent ornamentation, and we provide evidence that male UV coloration is condition dependent in this species. Spectral-reflection patterns change with male age and prior feeding history. The position of the UV band (i.e. UV hue) of the carapaces of younger (field-collected as subadults and matured as adults in laboratory) males shifted, relative to older (field-collected as adults) males, significantly towards longer wavelengths. Food deprivation significantly decreased the spectral intensity of the abdomen, but not the carapace. Questions concerning the mechanisms by which UV ornament...
Animal colour signals used in intraspecies communications can generally be attributed to a compos... more Animal colour signals used in intraspecies communications can generally be attributed to a composite effect of structural and pigmentary colours. Notably, the functional role of iridescent coloration that is 'purely' structural (i.e., absence of pigments) is poorly understood. Recent studies reveal that iridescent colorations can reliably indicate individual quality, but evidence of iridescence as a pure structural coloration indicative of male quality during contests and relating to an individual's resource-holding potential (RHP) is lacking. In age-and size-controlled pairwise male-male contests that escalate from visual displays of aggression to more costly physical fights, we demonstrate that the ultraviolet-green iridescence of Cosmophasis umbratica predicts individual persistence and relates to RHP. Contest initiating males exhibited significantly narrower carapace band separation (i.e., relative spectral positions of UV and green hues) than non-initiators. Asymmetries in carapace and abdomen brightness influenced overall contest duration and escalation. As losers retreated upon having reached their own persistence limits in contests that escalated to physical fights, losers with narrower carapace band separation were significantly more persistence. We propose that the carapace UV-green iridescence of C. umbratica predicts individual persistence and is indicative of a male's RHP. As the observed UV-green hues of C. umbratica are 'pure' optical products of a multilayer reflector system, we suggest that intrasexual variations in the optical properties of the scales' chitinair-chitin microstructures are responsible for the observed differences in carapace band separations.
Journal of Experimental Marine Biology and Ecology, 2011
Bright colours are a key visual signal in many animal communication systems. Here we examine the ... more Bright colours are a key visual signal in many animal communication systems. Here we examine the function of the blue-green facial bands found in two species of mangrove crabs, Perisesarma eumolpe (De Man) and P. indiarum (Tweedie). Food (mangrove leaves) ...
... such as shuttling, dropping, and pumping (A. argen-tata: Robinson & Robinson, 197... more ... such as shuttling, dropping, and pumping (A. argen-tata: Robinson & Robinson, 1970; A. appensa: Jackson et al., 1993; re-view: Cloudsley-Thompson, 1995; Rayor, 1996; Blackledge & Pickett, 2000; Blackledge & Wenzel, 2001). However, unlike many other orb-weaving spi ...
ABSTRACT Highlights ► We blocked reflections from Argiope versicolor web decorations at different... more ABSTRACT Highlights ► We blocked reflections from Argiope versicolor web decorations at different wavelengths. ► Only blocking UV reflections reduced number of Portia approaching webs. ► Thus UV is more important than other wavelengths for Portia to locate Argiope.
Stabilimenta, the conspicuous, ultraviolet (UV)-reflecting, white silk structures around the hub ... more Stabilimenta, the conspicuous, ultraviolet (UV)-reflecting, white silk structures around the hub of orb webs, are thought to increase a spider's foraging success by attracting prey (prey attraction hypothesis). No studies, however, have yet investigated the function of nonlinear and noncruciform stabilimenta and the stabilimenta of juvenile spiders. We examined whether the discoid stabilimenta spun by juvenile Argiope versicolor, an orb-spinning spider, function to attract prey. When we measured the UV reflectance of the web silks of A. versicolor juveniles, we found that the discoid stabilimentum silk, but not spiral silk or radial silk or the joint where the two types of silk met, reflected UV light. We then carried out two series of choice experiments in the laboratory to determine whether the webs with discoid stabilimenta attract more fruit flies than undecorated webs when UVC white light (300-700 nm) is present. We also examined whether the discoid stabilimenta still attract insects when the UV section of the spectrum (300-400 nm) is eliminated (UVÿ). Webs with discoid stabilimenta attracted more fruit flies than the webs without stabilimenta in UVC white light. However, in UVÿ light, fewer fruit flies flew to the webs, even when they were decorated with discoid stabilimenta. In a field experiment, significantly more insects were intercepted by webs with discoid stabilimenta than by webs without stabilimenta. We suggest that the discoid stabilimenta of A. versicolor juveniles act as a visual signal that attracts insects, supporting the prey attraction hypothesis.
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