Sexual dichromatism in the fur of a bat: An exploration of color differences and potential signaling functions.

Sex differences in body color (i.e., sexual dichromatism) are rare in bats and, more broadly, in mammals.

The recombination landscapes of spiny lizards (genus Sceloporus).

Despite playing a critical role in evolutionary processes and outcomes, relatively little is known about rates of recombination in the vast majority of species, including squamate reptiles-the second largest order of extant vertebrates, many species of which serve as important model organisms in evolutionary and ecological studies. This paucity of data has resulted in limited resolution on questions related to the causes and consequences of rate variation between species and populations, the determinants of within-genome rate variation, as well as the general tempo of recombination rate evolution on this branch of the tree of life. In order to address these questions, it is thus necessary to begin broadening our phylogenetic sampling.

Information out of the blue: phenotypic correlates of abdominal color patches in Sceloporus lizards.

Colorful ornaments are important visual signals for animal communication that can provide critical information about the quality of the signaler. In this study, we focused on different color characteristics of the abdominal patches of males of six lizard species from the genus Sceloporus. We addressed three main objectives.

Brain transcriptomic responses of Yarrow's spiny lizard, Sceloporus jarrovii, to conspecific visual or chemical signals.

Species with multimodal communication integrate information from social cues in different modalities into behavioral responses that are mediated by changes in gene expression in the brain. Differences in patterns of gene expression between signal modalities may shed light on the neuromolecular mechanisms underlying multisensory processing. Here, we use RNA-Seq to analyze brain transcriptome responses to either chemical or visual social signals in a territorial lizard with multimodal communication.

Steroid hormones, ectoparasites, and color: Sex, species, and seasonal differences in Sceloporus lizards.

Testosterone, in addition to promoting the expression of sexual ornaments can negatively affect immune function, leaving individuals more susceptible to parasites (immunocompetence handicap hypothesis). Immunosuppressive effects of testosterone also can occur indirectly, through increased glucocorticoid hormones (corticosterone, cortisol). Therefore, the expression of sexual ornaments and the ability to respond to parasites and diseases may be influenced by the interaction between testosterone and corticosterone.

Volatile fatty acid and aldehyde abundances evolve with behavior and habitat temperature in lizards.

Animal signals evolve by striking a balance between the need to convey information through particular habitats and the limitations of what types of signals can most easily be produced and perceived. Here, we present new results from field measures of undisturbed behavior and biochemical analyses of scent marks from 12 species of lizards to explore whether evolutionary changes in chemical composition are better predicted by measures of species behavior, particularly those associated with visual displays, chemoreception, and locomotion, or by measures of habitat climate (precipitation and temperature). We found that more active lizard species used fewer compounds in their volatile scent marks, perhaps conveying less specific information about individual and species identity.

Differences in cautiousness between mainland and island Podarcis siculus populations are paralleled by differences in brain noradrenaline/adrenaline concentrations.

Adaptive behavior is shaped by the type and intensity of selection pressures coming from the environment, such as predation risk and resource availability, and can be modulated by individual's neuroendocrine profile involving steroid hormones and the brain-stem monoaminergic circuits projecting to forebrain structures. Boldness when faced with a predator and exploration/activity when confronted with a new environment reflect the degree of cautiousness and/or "risk-taking" of an individual. In this study we have explored to which extent two populations of Podarcis siculus occupying different ecological niches: mainland (ML) and an islet (ISL) differ in the level of cautiousness and whether these differences are paralleled by differences in their monoaminergic profiles.

Structural Identification, Synthesis and Biological Activity of Two Volatile Cyclic Dipeptides in a Terrestrial Vertebrate.

Single substances within complex vertebrate chemical signals could be physiologically or behaviourally active. However, the vast diversity in chemical structure, physical properties and molecular size of semiochemicals makes identifying pheromonally active compounds no easy task. Here, we identified two volatile cyclic dipeptides, cyclo(L-Leu-L-Pro) and cyclo(L-Pro-L-Pro), from the complex mixture of a chemical signal in terrestrial vertebrates (lizard genus Sceloporus), synthesised one of them and investigated their biological activity in male intra-specific communication.

Melanization, α-melanocyte stimulating hormone and steroid hormones in male western fence lizards from nine populations.

Hormones can mediate suites of correlated traits. Melanocortins regulate melanin synthesis and elements of the melanocortin system can directly, and indirectly, affect a number of other traits, such as stress reactivity. Trait correlations within the melanocortin system have been studied mainly in birds and mammals but less so in reptiles.

Losing the trait without losing the signal: Evolutionary shifts in communicative colour signalling.

Colour signalling traits are often lost over evolutionary time, perhaps because they increase vulnerability to visual predators or lose relevance in terms of sexual selection. Here, we used spectrometric and phylogenetic comparative analyses to ask whether four independent losses of a sexually selected blue patch are spectrally similar, and whether these losses equate to a decrease in conspicuousness or to loss of a signal. We found that patches were lost in two distinct ways: either increasing reflectance primarily at very long or at very short wavelengths, and that species with additional colour elements (UV, green and pink) may be evolutionary intermediates.

Correlates of melanization in multiple high- and low-elevation populations of the lizard, Sceloporus occidentalis: Behavior, hormones, and parasites.

Hormones mediate the expression of suites of correlated traits and hence may act either to facilitate or constrain adaptive evolution. Selection on one trait within a hormone-mediated suite of traits may lead to a change in the strength of the hormone signal, causing changes in correlated traits. Growing evidence suggests that melanization, which is in part regulated by hormonal signals, is tightly linked to other traits, such as aggression and stress physiology.

Shaping communicative colour signals over evolutionary time.

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 lizards, and a detailed spectrophotometric analysis of four species to explore the specific forces shaping evolutionary change. We find that the ancestor of had blue patches.

Populations of the Lizard, Sceloporus occidentalis, that Differ in Melanization have Different Rates of Wound Healing.

Mechanisms underlying production of animal coloration can affect key traits besides coloration. Melanin, and molecules regulating melanin, can directly and indirectly affect other phenotypic traits, such as immune function. We asked whether melanization and a whole-organism measure of immune function are associated with wound healing.

Including Fossils in Phylogenetic Climate Reconstructions: A Deep Time Perspective on the Climatic Niche Evolution and Diversification of Spiny Lizards (Sceloporus).

Fossils and other paleontological information can improve phylogenetic comparative method estimates of phenotypic evolution and generate hypotheses related to species diversification. Here, we use fossil information to calibrate ancestral reconstructions of suitable climate for Sceloporus lizards in North America. Integrating data from the fossil record, general circulation models of paleoclimate during the Miocene, climate envelope modeling, and phylogenetic comparative methods provides a geographically and temporally explicit species distribution model of Sceloporus-suitable habitat through time.

Phenotypic correlates of melanization in two Sceloporus occidentalis (Phrynosomatidae) populations: Behavior, androgens, stress reactivity, and ectoparasites.

Mechanisms underlying production of animal coloration can affect key traits besides coloration. Melanin, and molecules regulating melanin, can directly and indirectly affect other phenotypic traits including aggression, stress-reactivity, and immune function. We studied correlation of melanization with these other traits, comparing within- and between-population differences of adult male western fence lizards, Sceloporus occidentalis.

Evolving from static to dynamic signals: evolutionary compensation between two communicative signals.

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 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 ( and ; and ).

Sex and species differences in plasma testosterone and in counts of androgen receptor-positive cells in key brain regions of Sceloporus lizard species that differ in aggression.

We studied neuroendocrine correlates of aggression differences in adults of two Sceloporus lizard species. These species differ in the degree of sex difference in aggressive color signals (belly patches) and in aggression: Sceloporus undulatus (males blue, high aggression; females white, low aggression) and Sceloporus virgatus (both sexes white, lower aggression). We measured plasma testosterone and counted cells expressing androgen receptor-like immunoreactivity to the affinity-purified polyclonal AR antibody, PG-21, in three brain regions of breeding season adults.

Stress and aversive learning in a wild vertebrate: the role of corticosterone in mediating escape from a novel stressor.

Elevated plasma corticosterone during stressful events is linked to rapid changes in behavior in vertebrates and can mediate learning and memory consolidation. We tested the importance of acute corticosterone elevation in aversive learning of a novel stressor by wild male eastern fence lizards (Sceloporus undulatus). We found that inhibiting corticosterone elevation (using metyrapone, a corticosterone synthesis blocker) during an encounter with a novel attacker impaired immediate escape responses and limited learning and recall during future encounters.

Acute corticosterone elevation enhances antipredator behaviors in male tree lizard morphs.

In response to stressful events, most vertebrates rapidly elevate plasma glucocorticoid levels. Corticosterone release stimulates physiological and behavioral responses that can promote survival while suppressing behaviors that are not crucial to immediate survival. Corticosterone also has preparatory effects for subsequent stressors.

Hormone levels in territorial and non-territorial male collared lizards.

For species displaying plastic alternative reproductive tactics, the relative plasticity hypothesis (RPH) combined with the positive relationship between androgens and aggression predicts higher androgen levels in more aggressive socially dominant males relative to less aggressive subordinate males (directional RPH). We tested this prediction of the directional RPH by comparing plasma levels of testosterone, dihydrotestosterone, and corticosterone in 2y+-collared lizard males that defended territories with those of first-year males that were mature, but did not defend territories. As expected, 2y+-males exhibited higher rates of advertisement, aggression, and courtship than first-year males.

Steroid correlates of multiple color traits in the spiny lizard, Sceloporus pyrocephalus.

Conspicuous coloration in females is less well studied compared to that in males. Adult female Mexican boulder spiny lizards (Sceloporus pyrocephalus) have conspicuously colored throat, or gular, regions, ranging from red to yellow, while adult males only weakly express such color in their gular region. Both sexes have dark blue-black gular stripes and venter stripes.

Environmental and endocrine correlates of tactic switching by nonterritorial male tree lizards (Urosaurus ornatus).

Animals often exhibit individual variation in their behavioral responses to the same stimuli in the biotic or abiotic environment. To elucidate the endocrine mechanisms mediating such behavioral variation, we have been studying a species of lizard with two distinct male phenotypes. Here we document behavioral variation across years in one of the two male phenotypes of the tree lizard, Urosaurus ornatus, and present hormone data that support an endocrine mechanism underlying this behavioral variation.