Femoral Gland Secretions Research Articles

Too much information? Males convey parasite levels using more signal modalities than females utilise.

Elaborate sexual signals are thought to have evolved and be maintained to serve as honest indicators of signaller quality. One measure of quality is health, which can be affected by parasite infection. Cnemaspis mysoriensis is a diurnal gecko that is often infested with ectoparasites in the wild, and males of this species express visual (coloured gular patches) and chemical (femoral gland secretions) traits that receivers could assess during social interactions. In this paper, we tested whether ectoparasites affect individual health, and whether signal quality is an indicator of ectoparasite levels. In wild lizards, we found that ectoparasite level was negatively correlated with body condition in both sexes. Moreover, some characteristics of both visual and chemical traits in males were strongly associated with ectoparasite levels. Specifically, males with higher ectoparasite levels had yellow gular patches with lower brightness and chroma, and chemical secretions with a lower proportion of aromatic compounds. We then determined whether ectoparasite levels in males influence female behaviour. Using sequential choice trials, wherein females were provided with either the visual or the chemical signals of wild-caught males that varied in ectoparasite level, we found that only chemical secretions evoked an elevated female response towards less parasitised males. Simultaneous choice trials in which females were exposed to the chemical secretions from males that varied in parasite level further confirmed a preference for males with lower parasites loads. Overall, we find that although health (body condition) or ectoparasite load can be honestly advertised through multiple modalities, the parasite-mediated female response is exclusively driven by chemical signals.

Carbonic anhydrase IV in lizard chemical signals

The evolution of chemical signals is subject to environmental constraints. A multicomponent signal may combine semiochemical molecules with supporting compounds able to enhance communication efficacy. Carbonic anhydrases (CAs) are ubiquitous enzymes catalysing the reversible hydration of carbon dioxide, a reaction involved in a variety of physiological processes as it controls the chemical environment of the different tissues or cellular compartments, thus contributing to the overall system homeostasis. CA-IV isoform has been recently identified by mass spectrometry in the femoral gland secretions (FG) of the marine iguana, where it has been hypothesized to contribute to the chemical stability of the signal, by regulating blend pH. Lizards, indeed, use FG to communicate by delivering the waxy secretion on bare substrate, where it is exposed to environmental stressors. Therefore, we expect that some molecules in the mixture may play supporting functions, enhancing the stability of the chemical environment, or even conferring homeostatic properties to the blend. CA-IV may well represent an important candidate to this hypothesized supporting/homeostatic function, and, therefore, we can expect it to be common in FG secretions of other lizard species. To evaluate this prediction and definitely validate CA identity, we analysed FG secretions of eight species of wall lizards (genus Podarcis), combining mass spectrometry, immunoblotting, immunocytochemistry, and transmission electron microscopy. We demonstrate CA-IV to actually occur in the FG of seven out of the eight considered species, providing an immunochemistry validation of mass-spectrometry identifications, and localizing the enzyme within the secretion mass. The predicted structure of the identified CA is compatible with the known enzymatic activity of CA-IV, supporting the hypothesis that CA play a signal homeostasis function and opening to new perspective about the role of proteins in vertebrate chemical communication.

Population differences in multimodal lizard communication are not well explained by habitat or history

AbstractAnimals evolve in complex selective regimes, where a suite of different factors can shape signal use. We might predict that more closely related species will exhibit more similar behavior than those more distantly related; however, sometimes signals are shaped more profoundly by the environment or other forces. Lizards in the genus Sceloporus communicate with conspecifics with multimodal signals that combine species‐typical push‐up and headbob displays and chemical signals in the form of femoral gland secretions. Here, we examine behavioral activity and signal use across three closely related populations of the Sceloporus undulatus species complex from diverse habitats across the United States, to test the relative roles of habitat and phylogeography in shaping communicative behavior. We filmed undisturbed levels of activity for free‐ranging males of S. consobrinus, syn. S. u. erythrocheilus, in Colorado, S. undulatus hyacinthinus in Indiana and S. u. undulatus in Georgia, and scored frequency and rates of behavior important for communication. We found that populations differed in their use of communicative signals in a way that deviates from expectations based solely on phylogeographic proximity or habitat, suggesting that plasticity or adaptation to conditions that vary among populations may be especially important. Specifically, canonical discriminant analyses found the largest differences in movement patterns. Sceloporus u. hyacinthinus was the most behaviorally different out of the three: males in this population had lower movement rates and particularly low levels of chemosensory behavior while male S. consobrinus and S. u. undulatus showed similar rates of chemosensory acts and headbob/push‐up displays. Phenotypic and environmental variation among closely related populations, in combination with phylogeographic knowledge can help us untangle the processes responsible for the origin and maintenance of organismal diversity in communicative behavior.

Sexual Selection and Proteinaceous Diversity in the Femoral Gland Secretions of Lacertid Lizards

Sexual selection contributes to the diversity of chemical signals in various animal groups. Lizards are good model species to study how sexual selection shapes signal diversity, as they are a chemically oriented taxonomic group with different levels of social interactions. Many lizard species bear epidermal glands secreting a waxy mixture of lipids and proteins, which are used in intraspecific communication. Previous among-species comparative analyses failed to find a relationship between the strength of sexual selection with the composition of the lipid blend in lizards. Here, we extend the investigation to the proteinaceous fraction. By using a phylogenetically informed approach, we correlated the average electrophoretic profiles of the protein from the femoral glands of 36 lacertid lizard species with the level of sexual dimorphism in size and shape, which are proxies for the strength of sexual selection. We found that as sexual size dimorphism advances, five distinct molecular weight regions in the protein profile increased their expression. Using tandem mass spectrometry, we successfully identified one of these five proteins: a carbonic anhydrase—an enzyme catalyzing the reversible hydration of carbon dioxide. Our findings suggest that proteins may be the target of sexual selection, as an active semiochemicals or as a dynamic support to other molecules: sexual selection may act indirectly on semiochemicals (namely lipids) by modifying the matrix (namely proteins).

Sexual selection and proteinaceous diversity in the femoral gland secretions of lacertid lizards

Sexual selection and proteinaceous diversity in the femoral gland secretions of lacertid lizards

Protein-lipid Association in Lizard Chemical Signals.

Chemical communication in terrestrial vertebrates is often built on complex blends, where semiochemical and structural compounds may form an integrated functional unit. In lizards, many species have specialized epidermal glands whose secretions are waxy, homogeneous blends of lipids and proteins, both active in communication. The intimate co-occurrence of such compounds allows us to hypothesize that they should undergo a certain degree of covariation, considering both their semiochemical role and the support-to-lipid function hypothesized for the protein fraction. In order to assess the occurrence and level of protein-lipid covariation, we compared the composition and complexity of the two fractions in the femoral gland secretions of 36 lizard species, combining phylogenetically-informed analysis with tandem mass spectrometry. We found the composition and complexity of the two fractions to be strongly correlated. The composition of the protein fraction was mostly influenced by the relative proportion of cholestanol, provitamin D3, stigmasterol, and tocopherol, while the complexity of the protein pattern increased with that of lipids. Additionally, two identified proteins (carbonic anhydrase and protein disulfide isomerase) increased their concentration as provitamin D3 became more abundant. Although our approach does not allow us to decrypt the functional relations between the proteinaceous and lipid components, nor under the semiochemical or structural hypothesis, the finding that the proteins involved in this association were enzymes opens up to new perspectives about protein role: They may confer dynamic properties to the blend, making it able to compensate predictable variation of the environmental conditions. This may expand the view about proteins in the support-to-lipid hypothesis, from being a passive and inert component of the secretions to become an active and dynamic one, thus providing cues for future research.

Evolutionary and biogeographical support for species-specific proteins in lizard chemical signals

Abstract The species-specific components of animal signals can facilitate species recognition and reduce the risks of mismatching and interbreeding. Nonetheless, empirical evidence for species-specific components in chemical signals is scarce and mostly limited to insect pheromones. Based on the proteinaceous femoral gland secretions of 36 lizard species (Lacertidae), we examine the species-specific component potential of proteins in lizard chemical signals. By quantitative comparison of the one-dimensional electrophoretic patterns of the protein fraction from femoral gland secretions, we first reveal that the protein composition is species specific, accounting for a large part of the observed raw variation and allowing us to discriminate species on this basis. Secondly, we find increased protein pattern divergence in sympatric, closely related species. Thirdly, lizard protein profiles show a low phylogenetic signal, a recent and steep increase in relative disparity and a high rate of evolutionary change compared with non-specifically signal traits (i.e. body size and shape). Together, these findings provide support for the species specificity of proteins in the chemical signals of a vertebrate lineage.

Patterns of Visual and Ultraviolet Reflectance in Femoral Gland Secretions of Two Desert Lizards

Femoral gland secretions in lizards convey chemical information about the health and social status of the depositing individual. These secretions influence behaviors related to female mate choice and male–male competition, but little is known about how they are first located by lizards in the environment. Secretions are visually conspicuous and can be sighted from a distance by visually adept lizards, but the specificity of secretion reflectance to the depositing species remains unknown. We examined the reflectance spectra of femoral gland secretions from two sympatric lizard species, Aspidoscelis tigris and Gambelia wislizenii, to determine whether secretions could be visually distinguished. Mean reflectance did not differ between species, but A. tigris had higher reflectance in ultraviolet wavelengths. For both species, lizards in better body condition, as determined by the residuals of the relationship between snout–vent length and body mass, had higher ultraviolet reflectance. In summary, our results indicate that femoral gland secretions can be visually discriminated between species if the discriminating lizard is ultraviolet sensitive.

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. Using an intruder challenge paradigm, we exposed 18 wild-caught, adult, male Sceloporus jarrovii to either male conspecific scents (femoral gland secretions placed on a small pebble), the species-specific push-up display (a programmed robotic model), or a control (an unscented pebble). We conducted differential expression analysis with both a de novo S. jarrovii transcriptome assembly and the reference genome of a closely related species, Sceloporus undulatus. Despite some inter-individual variation, we found significant differences in gene expression in the brain across signal modalities and the control in both analyses. The most notable differences occurred between chemical and visual stimulus treatments, closely followed by visual stimulus versus the control. Altered expression profiles could explain documented aggression differences in the immediate behavioral response to conspecific signals from different sensory modalities. Shared differentially expressed genes between visually- or chemically-stimulated males are involved in neural activity and neurodevelopment and several other differentially expressed genes in stimulus-challenged males are involved in conserved signal-transduction pathways associated with the social stress response, aggression and the response to territory intruders across vertebrates.

Composition and compound proportions affect the response to complex chemical signals in a spiny lizard

Most animal signals across sensory modalities are multicomponent traits that can be broken down into discrete elements. If different elements are perceived as unique, independent units (elemental perception), instead of as integrated percepts (configural perception), single changes in the presence/absence or the abundance of specific elements of a multicomponent signal may be enough to impact communication. Here, we found that male Yarrow’s spiny lizards (Sceloporus jarrovii) can discriminate single compounds of a multicomponent chemical signal (femoral gland secretions), different concentrations of a signaling compound, and a single compound from a mixture of compounds. In addition, one chemical compound elicited a response similar to that evoked by the complete natural scent. We conclude that perception of chemical signals in S. jarrovii lizards is elemental but also configural. The elemental perception of signaling compounds seems to occur with high sensitivity and narrow resolution, so that minor changes in single key elements may affect chemical communication. Given the multicomponent nature of most animal signals, hypotheses regarding signal function and evolution would be enhanced if researchers could determine whether these results apply to signals in other sensory modalities and identify the key elements of complex signals, from a receiver’s perspective. Most signals in animal communication are quite complex. For example, odors are mixtures of multiple volatile chemical compounds, and the way in which receivers perceive and process these mixtures to extract relevant information influences the structure and evolution of chemical signals. In a series of behavioral trials, we investigated how male Sceloporus jarrovii lizards may perceive conspecific odors by testing their response to individual and combined mixtures of two compounds present in femoral gland secretions at two different concentrations. We demonstrate that lizards can discriminate structurally similar compounds and that the response to a compound changes when said compound is part of a larger mixture. Compound concentration affected the perception of individual compounds but not complex mixtures. Deciphering what elements and/or configurations are perceived in an odor mixture is the only way to understand the role of mixture composition and its impact on communication.

Chemical signal divergence among populations influences behavioral discrimination in the whiptail lizard Aspidoscelis lineattissimus (squamata: teiidae)

Signal divergence and sensory preferences may lead to sexual isolation and eventually promote speciation between animal populations. However, few studies have quantified the degree of chemical signal divergence and scent-mediated sexual isolation in lizard populations. Geographic and ecological variations among populations of the whiptail lizard Aspidoscelis lineattissimus suggest that there might be chemical signal divergence among these populations. Here, we used gas chromatography-mass spectrometry to characterize and compare the chemical composition of the femoral gland secretions of male whiptail lizards of four populations from a western region of Mexico and, through behavioral experiments, explored the effects of lizard scents on precopulatory behaviors and intrasexual male-male chemical recognition among populations. Our results showed that males of each population contain a divergent mixture of compounds in their femoral gland secretions. Differential chemosensory behavior indicated that male and female lizards discriminated and were more attracted to scents of lizards from their same population. Although females also seem to discriminate male scents between populations, their associated preference to territories scent-marked by males of their own population is different between regions (eastern vs western) and not between populations. We suggest that between some populations of A. lineattissimus there may be partial premating isolation mediated by chemical signals and behavioral divergence. Geographic variation in sexual signals can strongly affect discrimination and recognition abilities among reproductive individuals from divergent populations, resulting in sexual isolation and speciation. Studies suggest that reproductive isolation and speciation in lizard systems may be mediated by chemical signals, male mate preferences, and male-male interactions but not by female mate preferences. Using gas chromatography-mass spectrometry techniques and behavioral experiments, we found that chemical divergence in femoral gland secretions of male Aspidoscelis lineattissimus influences behavioral discrimination among four distinct populations. Males and females recognized and responded more toward lizard scents from their own population. In addition, some female populations were able to discriminate between territories scent-marked by males from different populations. We suggest that chemical and behavioral differences between populations may influence partial premating isolation, which can be mediated by inter and intrasexual interactions.

Proteomics of Galápagos Marine Iguanas Links Function of Femoral Gland Proteins to the Immune System

Communication between individuals via molecules, termed chemosignaling, is widespread among animal and plant species. However, we lack knowledge on the specific functions of the substances involved for most systems. The femoral gland is an organ that secretes a waxy substance involved in chemical communication in lizards. Although the lipids and volatile substances secreted by the femoral glands have been investigated in several biochemical studies, the protein composition and functions of secretions remain completely unknown. Applying a proteomic approach, we provide the first attempt to comprehensively characterize the protein composition of femoral gland secretions from the Galápagos marine iguana. Using samples from several organs, the marine iguana proteome was assembled by next-generation sequencing and MS, resulting in 7513 proteins. Of these, 4305 proteins were present in the femoral gland, including keratins, small serum proteins, and fatty acid-binding proteins. Surprisingly, no proteins with discernible roles in partner recognition or inter-species communication could be identified. However, we did find several proteins with direct associations to the innate immune system, including lysozyme C, antileukoproteinase (ALP), pulmonary surfactant protein (SFTPD), and galectin (LGALS1) suggesting that the femoral glands function as an important barrier to infection. Furthermore, we report several novel anti-microbial peptides from the femoral glands that show similar action against Escherichia coli and Bacillus subtilis such as oncocin, a peptide known for its effectiveness against Gram-negative pathogens. This proteomics data set is a valuable resource for future functional protein analysis and demonstrates that femoral gland secretions also perform functions of the innate immune system.

Chemical characterization of the lipids in femoral gland secretions of wild male tegu lizards, Salvator merianae (Squamata, Teiidae) in comparison with captive-bred males.

Although chemical interactions play an essential role in lizard social behavior, the chemical composition of the femoral gland secretions that many lizards use for communication is known for only a few species, mainly European Lacertids. The tegu lizard, Salvator merianae, is the only species of the Teiidae family for which there is available information on lipids in femoral secretions, but only for captive bred males from Argentina. Here, based on mass spectra obtained by GC-MS, we found 69 lipophilic compounds in femoral gland secretions of wild males S.merianae from Brazil, including cholesterol and high amounts of saturated fatty acids (mainly hexadecanoic and octadecanoic). We found contrasting differences between wild and captive-bred males, which lack cholesterol but present high amount of 9,12-octadecadienoic acid. These within-species differences between wild and captive lizards strongly suggest the important influence of different diets on the chemical composition of the femoral gland secretion and suggest caution when interpreting results from captive animals, even in the same species.

Chemosensory discrimination of male age by female Psammodromus algirus lizards based on femoral secretions and feces

AbstractChemical communication plays an essential role in several social and reproductive behaviors of many animals. In lizards, the main sources of semiochemicals are femoral or pre‐anal gland secretions and feces. In male lizards Psammodromus algirus, there are age‐related differences in the chemical composition of femoral gland secretions and in the reproductive strategies, with older males defending territories and females, while younger males adopting sneak‐mating strategies. Females flee more often from mating advances of young males than from those of old males, which are more successful in obtaining matings. This suggests that age discrimination of males may be important for females. We tested here whether females showed differential chemosensory responses to chemical cues (femoral gland secretion and feces) of males of two age classes, and whether females use information from substrate scent marks of males of different ages to select where to stay. We found that females elicited more tongue‐flicks to the secretion and feces of old males than to control or secretion and feces of young males. Also, the time spent by females on a scented paper depended on the treatment, suggesting that females tended to spend more time on scent marks made with femoral secretions of old males. Adult females seemed capable to discriminate between young and old males based on chemical cues alone and showed more interest in scents of old males. However, substrate scent marks did not seem to entirely determine site selection by females, suggesting that females might need additional cues to perform the choice. These results can be explained by the different age‐dependent reproductive strategies of males, which can affect differentially to females.

Seasonal Variations in Femoral Gland Secretions Reveals some Unexpected Correlations Between Protein and Lipid Components in a Lacertid Lizard

Animals modulate intraspecific signal shape and intensity, notably during reproductive periods. Signal variability typically follows a seasonal scheme, traceable through the expression of visual, acoustic, chemical and behavioral patterns. The chemical channel is particularly important in lizards, as demonstrated by well-developed epidermal glands in the cloacal region that secrete lipids and proteins recognized by conspecifics. In males, the seasonal pattern of gland activity is underpinned by variation of circulating androgens. Changes in the composition of lipid secretions convey information about the signaler's quality (e.g., size, immunity). Presumably, individual identity is associated with a protein signature present in the femoral secretions, but this has been poorly investigated. For the first time, we assessed the seasonal variability of the protein signal in relation to plasma testosterone level (T), glandular activity and the concentration of provitamin D3 in the lipid fraction. We sampled 174 male common wall lizards (Podarcis muralis) over the entire activity season. An elevation of T was observed one to two months before the secretion peak of lipids during the mating season; such expected delay between hormonal fluctuation and maximal physiological response fits well with the assumption that provitamin D3 indicates individual quality. One-dimensional electrophoretic analysis of proteins showed that gel bands were preserved over the season with an invariant region; a result in agreement with the hypothesis that proteins are stable identity signals. However, the relative intensity of bands varied markedly, synchronously with that of lipid secretion pattern. These variations of protein secretion suggest additional roles of proteins, an issue that requires further studies.

Morph-specific protein patterns in the femoral gland secretions of a colour polymorphic lizard

Colour polymorphism occurs when two or more genetically-based colour morphs permanently coexist within an interbreeding population. Colouration is usually associated to other life-history traits (ecological, physiological, behavioural, reproductive …) of the bearer, thus being the phenotypic marker of such set of genetic features. This visual badge may be used to inform conspecifics and to drive those decision making processes which may contribute maintaining colour polymorphism under sexual selection context. The importance of such information suggests that other communication modalities should be recruited to ensure its transfer in case visual cues were insufficient. Here, for the first time, we investigated the potential role of proteins from femoral gland secretions in signalling colour morph in a polymorphic lizard. As proteins are thought to convey identity-related information, they represent the ideal cues to build up the chemical modality used to badge colour morphs. We found strong evidence for the occurrence of morph-specific protein profiles in the three main colour-morphs of the common wall lizard, which showed both qualitative and quantitative differences in protein expression. As lizards are able to detect proteins by tongue-flicking and vomeronasal organ, this result support the hypothesis that colour polymorphic lizards may use a multimodal signal to inform about colour-morph.

Characterization of lipid structures in femoral secretions of Galápagos marine iguanas by shotgun lipidomics

The lipidome of femoral gland secretions of the marine iguana (Amblyrhynchus cristatus) was studied. The main aim of this work was to identify and quantify the lipids present in femoral secretions using mass spectrometry-based shotgun lipidomics. Lipids belonging to seven lipid classes were identified: ceramides (43.41%), triacylglycerols (42.15%), cholesteryl esters (4.18%), sphingomyelins (3.61%), phosphatidylcholines (2.67%), phosphatidylinositols (2.50%) and phosphatidylethanolamines (1.48%). The second aim of the study was to explore whether lipid composition matches the different subspecies or populations of marine iguanas. The different subspecies of iguanas did not group together in relation to their lipidome. The authors’ findings are discussed in an ecological context and compared with the results of a previous study that characterized volatile lipids in marine iguana secretions using gas chromatography. Given the high diversity of lipid structures in femoral secretions discovered in this study, it is likely that some of these could be involved in intraspecific communication. Certain lipids could have other functions, such as building a barrier to avoid water loss. More data needs to be added to explore this hypothesis. This study is the first to use a lipidomics-based approach to characterize lipid composition in lizard femoral secretions. The application of shotgun lipidomics to reptilian glandular secretions will shed new light on the potential function of lipids in intraspecific chemical communication.

Interpopulational and seasonal variation in the chemical signals of the lizard Gallotia galloti.

Communicative traits are strikingly diverse and may vary among populations of the same species. Within a population, these traits may also display seasonal variation. Chemical signals play a key role in the communication of many taxa. However, we still know far too little about chemical communication in some vertebrate groups. In lizards, only a few studies have examined interpopulational variation in the composition of chemical cues and signals and only one study has explored the seasonal effects. Here we sampled three subspecies of the Tenerife lizards (Gallotia galloti) and analyze the lipophilic fraction of their femoral gland secretions to characterize the potential interpopulational variation in the chemical signals. In addition, we assessed whether composition of these secretions differed between the reproductive and the non-reproductive season. We analyzed variations in both the overall chemical profile and the abundance of the two main compounds (cholesterol and vitamin E). Our results show interpopulational and seasonal differences in G. gallotia chemical profiles. These findings are in accordance with the high interpopulational variability of compounds observed in lizard chemical signals and show that their composition is not only shaped by selective factors linked to reproductive season.

Diversity of compounds in femoral secretions of Galápagos iguanas (genera: Amblyrhynchus and Conolophus), and their potential role in sexual communication in lek-mating marine iguanas (Amblyrhynchus cristatus).

BackgroundChemical signals are widely used in the animal kingdom, enabling communication in various social contexts, including mate selection and the establishment of dominance. Femoral glands, which produce and release waxy secretions into the environment, are organs of central importance in lizard chemical communication. The Galápagos marine iguana (Amblyrhynchus cristatus) is a squamate reptile with a lek-mating system. Although the lekking behaviour of marine iguanas has been well-studied, their potential for sexual communication via chemical cues has not yet been investigated. Here we describe the diversity of the lipophilic fraction of males’ femoral gland secretions among 11 island populations of marine iguanas, and compare it with the composition of its sister species, the Galápagos land iguana (Conolophus subcristatus). We also conducted behavioural observations in marine iguana territorial males in order to explore the possible function of these substances in the context of male dominance in leks.MethodsFemoral secretions were analysed by gas chromatography coupled to mass spectrometry (GC–MS), and chromatography with a flame ionisation detector (GC-FID) in order to characterise the lipophilic composition. To understand the potential role of femoral secretions in marine iguana intraspecific communication, territorial males were sampled for their femoral glands and monitored to record their head bob rate—a territorial display behaviour in males—as well as the number of females present in their leks.ResultsWe found that the gland secretions were composed of ten saturated and unsaturated carboxylic acids ranging in chain length between C16 and C24, as well as three sterols. Cholesterol was the main compound found. Intriguingly, land iguanas have a higher diversity of lipophilic compounds, with structural group of lipids (i.e. aldehydes) entirely absent in marine iguanas; overall the chemical signals of both species were strongly differentiated. Lipid profiles also differed among populations of marine iguanas from different islands, with some islands demonstrating a high diversity of lipophilic compounds (i.e. full spectra of compounds), and others lacking one or more compounds. Among the compounds most frequently found missing were 11- and 13-eicosenoic acids. Gland secretions of males with a better body condition and with a higher dominance status (i.e. those accompanied by females and with higher head bob display) were proportionately richer in C20-unsaturated fatty acids (11-eicosenoic acid).DiscussionLand and marine iguanas strongly diverged in their chemical composition of the femoral glands likely due to ecological differences between both species. Despite that marine iguana populations varied in their femoral gland composition that was not related to their genetic structure. Our results indicated that 11-eicosenoic acid may play an important role in intraspecific chemical communication in marine iguanas.

Variations in chemical sexual signals of Psammodromus algirus lizards along an elevation gradient may reflect altitudinal variation in microclimatic conditions.

Chemical signals used in intraspecific communication are expected to evolve or to show phenotipic plasticity to maximize efficacy in the climatic conditions of a given environment. Elevational environmental gradients in mountains provide a good opportunity to test this hypothesis by examining variation in characteristics of signals in species found across different elevations with different climatic conditions. We analyzed by gas chromatography-mass spectrometry (GC-MS) the lipophilic fraction of the femoral gland secretions of male lizards Psammodromus algirus (Fam. Lacertidae) from six localities located along a 2200m elevational gradient at Sierra Nevada Mountains (SE Spain). There was elevational clinal variation in climatic variables, number of femoral pores and in the relative proportions of some classes of compounds (i.e., ethyl esters of fatty acids, waxy esters, and aldehydes) but not others. We discuss how this variation would result in different physicochemical properties of the entire femoral secretion, which might help optimize the efficacy of chemical signals under the particular microclimatic conditions at each elevation.