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1.  Shaping communicative colour signals over evolutionary time 
Royal Society Open Science  2016;3(11):160728.
Many evolutionary forces can shape the evolution of communicative signals, and the long-term impact of each force may depend on relative timing and magnitude. We use a phylogenetic analysis to infer the history of blue belly patches of Sceloporus lizards, and a detailed spectrophotometric analysis of four species to explore the specific forces shaping evolutionary change. We find that the ancestor of Sceloporus had blue patches. We then focus on four species; the first evolutionary shift (captured by comparison of S. merriami and S. siniferus) represents an ancient loss of the belly patch by S. siniferus, and the second evolutionary shift, bounded by S. undulatus and S. virgatus, represents a more recent loss of blue belly patch by S. virgatus. Conspicuousness measurements suggest that the species with the recent loss (S. virgatus) is the least conspicuous. Results for two other species (S. siniferus and S. merriami) suggest that over longer periods of evolutionary time, new signal colours have arisen which minimize absolute contrast with the habitat while maximizing conspicuousness to a lizard receiver. Specifically, males of the species representing an ancient loss of blue patch (S. siniferus) are more conspicuous than are females in the UV, whereas S. merriami males have evolved a green element that makes their belly patches highly sexually dimorphic but no more conspicuous than the white bellies of S. merriami females. Thus, our results suggest that natural selection may act more immediately to reduce conspicuousness, whereas sexual selection may have a more complex impact on communicative signals through the introduction of new colours.
doi:10.1098/rsos.160728
PMCID: PMC5180159  PMID: 28018661
sex differences; animal coloration; visual communication; natural selection; sexual selection; Sceloporus lizards
2.  Behavioral Plasticity in Response to Environmental Manipulation among Zebrafish (Danio rerio) Populations 
PLoS ONE  2015;10(4):e0125097.
Plastic responses can have adaptive significance for organisms occurring in unpredictable environments, migratory species and organisms occupying novel environments. Zebrafish (Danio rerio) occur in a wide range of habitats and environments that fluctuate frequently across seasons and habitats. We expect wild populations of fish to be behaviorally more flexible than fish reared in conventional laboratory and hatchery environments. We measured three behavioral traits among 2 wild (U and PN) and 1 laboratory bred (SH) zebrafish populations in four environments differing in water flow and vegetation regimes. We found that the degree of plasticity varied with the type of behavior and also among populations. In general, vegetation increased aggression and water flow decreased latency to feed after a disturbance, but the patterns were population dependent. For example, while wild U fish fed more readily after a disturbance in vegetated and/or flowing habitats, fish from the wild PN population and lab-reared SH strain showed little variation in foraging across different environmental conditions. Zebrafish from all the three populations were more aggressive when tested in an arena with vegetation. In contrast, while there was an inter- population difference in shoaling distances, variation in shoaling distance across environmental conditions within populations was not significant. These results suggest that both foraging and aggression in zebrafish are more plastic and influenced by immediate context than is shoaling distance, which may have a stronger genetic basis. Our findings point to different underlying mechanisms influencing the expression of these traits and warrants further investigations.
doi:10.1371/journal.pone.0125097
PMCID: PMC4415955  PMID: 25927838
3.  Evolving from static to dynamic signals: evolutionary compensation between two communicative signals 
Animal behaviour  2015;102:223-229.
Signals that convey related information may impose selection on each other, creating evolutionary links between different components of the communicative repertoire. Here, we ask about the consequences of the evolutionary loss of one signal (a colour patch) on another (a motion display) in Sceloporus lizards. We present data on male lizards of four species: two pairs of sister taxa representing two independent evolutionary losses of the static colour patch (Sceloporus cozumelae and Sceloporus parvus; Sceloporus siniferus and Sceloporus merriami). Males of the two species that have undergone an evolutionary loss of blue-belly patches (S. cozumelae, S. siniferus) were less active than their blue-bellied sister taxa (S. parvus, S. merriami), consistent with the suggestion that the belly patches were lost to reduce conspicuousness of species with high predation pressure. In contrast, the headbob display appears to have become more, rather than less, conspicuous over evolutionary time. The colour patch is exhibited primarily during aggressive encounters, whereas headbob displays are multifunction signals used in several different contexts, including aggressive encounters. Males of species that have lost the colour patch produced more motion displays, and the structure of those motion displays were more similar to those produced during combat. In both evolutionary episodes, a static colour signal appears to have been replaced by dynamic motion displays that can be turned off in the presence of predators and other unwanted receivers. The predominant pattern is one of evolutionary compensation and interactions between multiple signals that convey related information.
PMCID: PMC4400845  PMID: 25892737
communicative display; conspicuous visual signal; dynamic signal; evolutionary compensation; multimodal signal; Sceloporus; static signal
4.  Trade-offs between reproductive coloration and innate immunity in a natural population of female sagebrush lizards, Sceloporus graciosus 
The Herpetological journal  2011;21(2):131-134.
Trade-offs between immune function and reproduction are common to many organisms. Nevertheless, high energetic resources may eliminate the need for these trade-offs. In this study, we consider the effects of food availability on these trade-offs in a wild population of female sagebrush lizards (Sceloporus graciosus) during the breeding season. We manipulated food availability by supplementing some lizards but not others. We measured female orange side coloration as an indicator of reproductive state and calculated the bacterial killing capability of collected plasma exposed to Escherichia coli ex vivo as a measure of innate immunity. We found that female lizards show a natural trade-off between reproductive effort and immune function; females under high reproductive investment had lower innate immunity than those at a later reproductive state. We did not detect this trade-off with food supplementation. We show that trade-offs depend on the energetic state of the animal, illustrating that trade-offs between immune function and reproduction can be context-dependent.
PMCID: PMC4231297  PMID: 25400312
context-dependent; energetics; life history; resources
5.  Socially-Central Zebrafish Influence Group Behavior More than Those on the Social Periphery 
PLoS ONE  2013;8(1):e55503.
Certain individuals are more effective than others at using individual experience to impact group behavior. Here, we tested whether pre-training of zebrafish that are at the focal central of social group dynamics (“Key” fish) has a stronger positive impact on group performance than does pre-training of less central (“Non-Key”) fish. We used very short observation periods and social network statistics to identify Key and Non-Key individuals, trained these fish to respond to an aversive stimulus, and then measured group performance after returning these now-experienced fish to a social setting. Although Key and Non-Key fish evaded the stimulus equally quickly as individuals, groups with experienced Key fish escaped the aversive stimulus more quickly than did groups with experienced Non-Key fish. The impact depended on genetic background: PN zebrafish on the social extremes (more often males) influenced the group's baseline response to the aversive stimulus, whereas experienced Scientific Hatcheries' zebrafish (both males and females) influenced the change in response over repeated trials. These results suggest that social roles are an important feature of information transfer across a group, and set the stage for future research into the genetic and evolutionary basis of social learning.
doi:10.1371/journal.pone.0055503
PMCID: PMC3561195  PMID: 23383208
6.  Food supplementation and testosterone interact to influence reproductive behavior and immune function in Sceloporous graciosus 
Hormones and behavior  2009;57(2):134.
The energetic resources in an organism’s environment are essential for executing a wide range of life history functions, including immunity and reproduction. Most energetic budgets, however, are limited, which can lead to trade-offs among competing functions. Increasing reproductive effort tends to decrease immunity in many cases; and increasing total energy via supplemental feedings can eliminate this effect. Testosterone (T), an important regulator of reproduction, and food availability are thus both potential factors regulating life-history processes, yet they are often tested in isolation of each other. In this study, we considered the effect of both food availability and elevated T on immune function and reproductive behavior in sagebrush lizards, Sceloporus graciosus, to assess how T and energy availability affect these trade-offs. We experimentally manipulated diet (via supplemental feedings) and T (via dermal patches) in males from a natural population. We determined innate immune response by calculating the bacterial killing capability of collected plasma exposed to E. coli ex vivo. We measured reproductive behavior by counting the number of courtship displays produced in a 20-min sampling period. We observed an interactive effect of food availability and T-patch on immune function, with food supplementation increasing immunity in T-patch lizards. Additionally, T increased courtship displays in control food lizards. Lizards with supplemental food had higher circulating T than controls. Collectively, this study shows that the energetic state of the animal plays a critical role in modulating the interactions among T, behavior and immunity in sagebrush lizards and likely other species.
doi:10.1016/j.yhbeh.2009.09.019
PMCID: PMC2814879  PMID: 19800885
Context-dependent; Energy allocation; Innate immunity; Life history; Resources; Sceloporus; Trade-offs
7.  Sex-specific visual performance: female lizards outperform males in motion detection 
Biology Letters  2009;5(6):732-734.
In animal communication, complex displays usually have multiple functions and, male and female receivers often differ in their utilization and response to different aspects of these displays. The perceptual variability hypothesis suggests that different aspects of complex signals differ in their ability to be detected and processed by different receivers. Here, we tested whether receiver male and female Sceloporus graciosus lizards differ in visual motion detection by measuring the latency to the visual grasp response to a motion stimulus. We demonstrate that in lizards that largely exhibit complex motions as courtship signals, female lizards are faster than males at visually detecting motion. These results highlight that differential signal utilization by the sexes may be driven by variability in the capacity to detect different display properties.
doi:10.1098/rsbl.2009.0348
PMCID: PMC2827977  PMID: 19656865
sex difference; visual performance; motion detection; complex signals; animal communication; Sceloporus graciosus
8.  Courtship attention in sagebrush lizards varies with male identity and female reproductive state 
Behavioral Ecology  2008;19(6):1326-1332.
Previous experiments suggest that males spend more time with the more receptive of 2 novel females or the one with the higher fitness potential. However, males often court individual females repeatedly over a season; for example, male lizards sequentially visit familiar females as they patrol territorial boundaries. It may benefit males to vary display intensity as they move between multiple females. In this study, we explored the factors influencing amount of male courtship to familiar females in the sagebrush lizard, Sceloporus graciosus. We tested whether males vary the amount of courtship exhibited due to individual differences among males, female reproductive state, or female fitness potential. Each male was allowed to interact separately, but repeatedly, with 2 females until both females laid eggs. Male courtship behavior with each of the 2 females was assayed at an intermediate point, after 3 weeks of interaction. We found that individual differences among males were considerable. The number of male courtship displays was also positively correlated with female latency to lay eggs, with males displaying more often toward females with eggs that had not yet been fertilized. Courtship behavior was not well predicted by the number of eggs laid or by female width, both measures of female quality. Thus, male S. graciosus appear to alter courtship intensity more in response to signals of female reproductive state than in response to variation in potential female fitness.
doi:10.1093/beheco/arn072
PMCID: PMC2583109  PMID: 19458780
courtship; male choice; mate choice; reproductive state; Sceloporus graciosus; sexual selection
9.  Courtship attention in sagebrush lizards varies with male identity and female reproductive state 
Previous experiments suggest that males spend more time with the more receptive of two novel females or the one with the higher fitness potential. However, males often court individual females repeatedly over a season; for example, male lizards sequentially visit familiar females as they patrol territorial boundaries. It may benefit males to vary display intensity as they move between multiple females. In this study, we explored the factors influencing amount of male courtship to familiar females in the Sagebrush lizard, Sceloporus graciosus. We tested whether males vary the amount of courtship exhibited due to individual differences among males, female reproductive state, or female fitness potential. Each male was allowed to interact separately, but repeatedly, with two females until both females laid eggs. Male courtship behavior with each of the two females was assayed at an intermediate point, after three weeks of interaction. We found that individual differences among males were considerable. The number of male courtship displays was also positively correlated with female latency to lay eggs, with males displaying more often towards females with eggs that had not yet been fertilized. Courtship behavior was not well predicted by the number of eggs laid or by female width, both measures of female quality. Thus, male S. graciosus appear to alter courtship intensity more in response to signals of female reproductive state than in response to variation in potential female fitness.
doi:10.1093/beheco/arn072
PMCID: PMC2583109  PMID: 19458780
Sceloporus graciosus; male choice; mate choice; sexual selection; reproductive state; courtship

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