Matching Items (4)

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Heritability of Elaborate Coloration in the Pipevine Swallowtail, Battus philenor

Description

Two primary contexts for the adaptive evolution of bright coloration are competition for mates (i.e. mate choice) and avoiding predator attacks (i.e. warning coloration). Bright animal coloration can be iridescent,

Two primary contexts for the adaptive evolution of bright coloration are competition for mates (i.e. mate choice) and avoiding predator attacks (i.e. warning coloration). Bright animal coloration can be iridescent, in which the surface appears to change color with changing viewing or illumination angle. Bright animal coloration can also be produced by pigments, which do not appear to change color with changing viewing or illumination angle. The Pipevine Swallowtail, Battus philenor, is unique in having both sexual signals and warning coloration that include iridescent and pigment components, both of which are variable in color. The aim of our study was to examine the role genes play in producing this variation, providing us a sense of potential indirect benefits of female choice. We tested the hypothesis that color variation has a genetic component. We predicted that in a full-sib analysis there should be greater variation in the coloration of the sexual and warning signal among families than within families. We reared B. philenor under standard laboratory conditions and analyzed heritability using a full-sib analysis. We collected reflectance measurements for components of the sexual and warning signal iridescence using a spectrophotometer and used CLR (color analysis software) to extract brightness, hue, and chroma values. We used a multivariate ANOVA (IBM SPSS, v. 21) to analyze the warning signal variation, and a generalized linear mixed model (IBM SPSS, v. 21) to analyze the sexual versus warning signal variation in males. A significance value of 0.05 was used for both analyses. Our results indicated a genetic component to coloration, implicating indirect benefits in B. philenor female mate bias. Further research on bright coloration in B. philenor indicates that there may also be direct benefits of female mate choice.

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Created

Date Created
  • 2014-12

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The costs and consequences of iridescent coloration in Anna's hummingbirds (Calypte anna)

Description

Colorful ornaments in animals often serve as sexually selected signals of quality. While pigment-based colors are well-studied in these regards, structural colors that result from the interaction of light with

Colorful ornaments in animals often serve as sexually selected signals of quality. While pigment-based colors are well-studied in these regards, structural colors that result from the interaction of light with photonic nanostructures are comparatively understudied in terms of their consequences in social contexts, their costs of production, and even the best way to measure them. Iridescent colors are some of the most brilliant and conspicuous colors in nature, and I studied the measurement, condition-dependence, and signaling role of iridescence in Anna's hummingbirds (Calypte anna). While most animal colors are easily quantified using well-established spectrophotometric techniques, the unique characteristics of iridescent colors present challenges to measurement and opportunities to quantify novel color metrics. I designed and tested an apparatus for careful control and measurement of viewing geometry and highly repeatable measurements. These measurements could be used to accurately characterize individual variation in iridescent Anna's hummingbirds to examine their condition-dependence and signaling role. Next, I examined the literature published to date for evidence of condition-dependence of structural colors in birds. Using meta-analyses, I found that structural colors of all three types - white, ultra-violet/blue, and iridescence - are significantly condition-dependent, meaning that they can convey information about quality to conspecifics. I then investigated whether iridescent colors were condition-dependent in Anna's hummingbirds both in a field correlational study and in an experimental study. Throughout the year, I found that iridescent feathers in both male and female Anna's hummingbirds become less brilliant as they age. Color was not correlated with body condition in any age/sex group. However, iridescent coloration in male Anna's hummingbirds was significantly affected by experimental protein in the diet during feather growth, indicating that iridescent color may signal diet quality. Finally, I examined how iridescent colors were used to mediate social competitions in male and female Anna's hummingbirds. Surprisingly, males that were less colorful won significantly more contests than more colorful males, and colorful males received more aggression. Less colorful males may be attempting to drive away colorful neighbors that may be preferred mates. Female iridescent ornament size and color was highly variable, but did not influence contest outcomes or aggression.

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Created

Date Created
  • 2012

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The Evolution of Hummingbird Coloration and Courtship Displays

Description

Animals have evolved a diversity of signaling traits, and in some species, they co-occur and are used simultaneously to communicate. Although much work has been done to understand why animals

Animals have evolved a diversity of signaling traits, and in some species, they co-occur and are used simultaneously to communicate. Although much work has been done to understand why animals possess multiple signals, studies do not typically address the role of inter-signal interactions, which may vary intra- and inter-specifically and help drive the evolutionary diversity in signals. For my dissertation, I tested how angle-dependent structural coloration, courtship displays, and the display environment interact and co-evolved in hummingbird species from the “bee” tribe (Mellisugini). Most “bee” hummingbird species possess an angle-dependent structurally colored throat patch and stereotyped courtship (shuttle) display. For 6 U.S. “bee” hummingbird species, I filmed male shuttle displays and mapped out the orientation- and-position-specific movements during the displays. With such display paths, I was able to then recreate each shuttle display in the field by moving plucked feathers from each male in space and time, as if they were naturally displaying, in order to measure each male’s color appearance during their display (i.e. the interactions between male hummingbird plumage, shuttle displays, and environment) from full-spectrum photographs. I tested how these interactions varied intra- and inter-specifically, and which of these originating traits might explain that variation. I first found that the solar-positional environment played a significant role in explaining variation in male color appearance within two species (Selasphorus platycercus and Calypte costae), and that different combinations of color-behavior-environment interactions made some males (in both species) appear bright, colorful, and flashy (i.e. their color appearance changes throughout a display), while other males maintained a consistent (non-flashing) color display. Among species, I found that plumage flashiness positively co-varied with male display behaviors, while another measure of male color appearance (average brightness/colorfulness) co-varied with the feather reflectance characteristics themselves. Additionally, species that had more exaggerated plumage features had less exaggerated shuttle displays. Altogether, my dissertation work illustrates the complexity of multiple signal evolution and how color-behavior-environment interactions are vital to understanding the evolution of colorful and behavioral display traits in animals.

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Created

Date Created
  • 2018

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Color and communication in Habronattus jumping spiders: tests of sexual and ecological selection

Description

Differences between males and females can evolve through a variety of mechanisms, including sexual and ecological selection. Because coloration is evolutionarily labile, sexually dichromatic species are good models for understanding

Differences between males and females can evolve through a variety of mechanisms, including sexual and ecological selection. Because coloration is evolutionarily labile, sexually dichromatic species are good models for understanding the evolution of sex differences. While many jumping spiders exhibit diverse and brilliant coloration, they have been notably absent from such studies. In the genus Habronattus, females are drab and cryptic while males are brilliantly colored, displaying some of these colors to females during elaborate courtship dances. Here I test multiple hypotheses for the control and function of male color. In the field, I found that Habronattus males indiscriminately court any female they encounter (including other species), so I first examined the role that colors play in species recognition. I manipulated male colors in H. pyrrithrix and found that while they are not required for species recognition, the presence of red facial coloration improves courtship success, but only if males are courting in the sun. Because light environment affects transmission of color signals, the multi-colored displays of males may facilitate communication in variable and unpredictable environments. Because these colors can be costly to produce and maintain, they also have the potential to signal reliable information about male quality to potential female mates. I found that both red facial and green leg coloration is condition dependent in H. pyrrithrix and thus has the potential to signal quality. Yet, surprisingly, this variation in male color does not appear to be important to females. Males of many Habronattus species also exhibit conspicuous markings on the dorsal surface of their abdomens that are not present in females and are oriented away from females during courtship. In the field, I found that these markings are paired with increased leg-waving behavior in a way that resembles the pattern and behavior of wasps; this may provide protection by exploiting the aversions of predators. My data also suggest that different activity levels between the sexes have placed different selection pressures on their dorsal color patterns. Overall, these findings challenge some of the traditional ways that we think about color signaling and provide novel insights into the evolution of animal coloration.

Contributors

Agent

Created

Date Created
  • 2012