Lizard Liolaemus Research Articles

Testing the Accuracy of Fecal-Based Analyses in Studies of Trophic Ecology in Lizards

Trophic niche studies are essential for evaluating ecological interactions between and within species and their evolutionary implications. For example, fundamental aspects of a wide range of hypotheses concerning population divergence, evolution of sexual dimorphism, and adaptations to fluctuating environments rely on dietary evidence. The accuracy of different methodologies used to estimate trophic specializations is therefore a fundamental issue. Under the assumption that direct observations of gastric contents provide accurate information about dietary preferences, I examined how reliably diet is reflected in fecal pellets. I conducted two main comparative tests on living lizards. First, I fed individuals of 23 species with hard- and soft-bodied organisms, and compared fecal pellets. Second, I examined prey items from natural diets represented in feces and gastric contents (stomach-flushing) in a wild population of the lizard Liolaemus tenuis. My results reveal that fecal samples provide inaccurate estimates of lizard trophic preferences, mainly because soft-bodied organisms are destroyed by digestive processes. Even though soft-bodied prey may be essential dietary items (as inferred from gastric analysis), these organisms may be almost entirely absent from feces. I suggest that direct gastric analyses should be the preferred method for analyzing reptilian diets.

Chemical self-recognition in the lizard Liolaemus fitzgeraldi

Social–chemical recognition is exhibited by all the Liolaemus lizards tested to date, except Liolaemus fitzgeraldi, which during post-hibernation did not discriminate chemosignals of same-sex individuals from a control. To clarify if L. fitzgeraldi is unique among the studied Liolaemus in lacking social–chemical recognition or if this was previously undetected, we recorded behavior during pre- and post-hibernation when confronted with chemosignals of conspecifics and from themselves. L fitzgeraldi showed self-recognition and seasonal changes in two exploratory behaviors. Potentially, conspecific recognition in L fitzgeraldi was undetected due to seasonality, but this species may rely comparatively less on chemical communication than congeners.

Legitimate seed dispersal by lizards in an alpine habitat: The case of Berberis empetrifolia (Berberidaceae) dispersed by Liolaemus belii (Tropiduridae)

In this study we determined the effect of seed passage through Liolaemus bellii lizard digestive tracts on germination of fleshy-fruited Andean shrub species Berberis empetrifolia (Berberidaceae), and evaluated the effect of this passage on seed coat characteristics. In addition, we assessed the spatial patterns of fecal deposition by lizards onto various microhabitats available in the Andean environments of central Chile. The germination rate and the final percentage of lizard-ingested B. empetrifolia seeds was greater than control seeds. Comparing photographs and seed coat histological cuts, we suggest that the cutine wax present on seed coats from lizard-ingested seeds was probably removed by abrasion inside the lizards’ digestive tract. Sixty-two percent of the lizard’s feces was deposited on bare soil near rocks commonly inhabited by lizards. However, this microhabitat represents only 29% of the available ground cover at the study site. By enhancing seed germination and depositing seeds onto potential safe sites for recruitment, the lizard Liolaemus bellii is acting, at least qualitatively, as an effective disperser of Berberis empetrifolia.

A NEW ENDEMIC SPECIES OF LIOLAEMUS (IGUANIA: LIOLAEMIDAE) FROM THE MOUNTAIN RANGE OF TANDILIA, BUENOS AIRES PROVINCE, ARGENTINA

Liolaemus gracilis was cited in the categorization of the reptile habitat associations of Buenos Aires province in Argentina as the only Liolaemus lizard inhabiting the rocky grounds of the Tandilia System. We describe a new species of the genus Liolaemus which was previously confused with the widely ranging L. gracilis from the population of this mountain range. We examined samples of populations from coastal sand dunes and from the mountain range of Tandilia. Morphological characters and measurements were taken from specimens of both populations. We recorded ecological and life history notes of the saxicolous form in the field. The new species is an endemic and saxicolous form from Tandilia that can be distinguished from L. gracilis by indistinct or absent light dorsolateral stripes, small and segmental paravertebral spots, and by a throat with a denser, fine and diffuse spotted pattern. The ventral coloration is grayish plumb. Temporal scales are keeled or slightly keeled and the auricular scale is less differentiated. Morphometrically, the new species is larger in snout–vent length and head width but smaller in maximum body width and tail length than L. gracilis. The new species is oviparous and insectivorous.

Annual activity of the lizard Liolaemus occipitalis (Squamata, Liolaemidae) in the coastal sand dunes of southern Brazil

The activity pattern of the small sand lizard, Liolaemus occipitalis Boulenger, 1885, was investigated in the coastal sand dunes at Quintão beach (Palmares do Sul, southern, Brazil), between September 1998 and August 1999. The results showed that L. occipitalis is active all along the year, but with variations in its daily and seasonal activity patterns associated to climatic changes in the habitat. Lizard activity pattern was distributed as follows: under the sand, burrowed (73%), under vegetation (14%), dislocation (7%) and basking (6%). Mean habitat temperatures (air and substrate) were significantly different. The results indicate that L. occipitalis is a thigmothermic and heliothermic species that regulates its body temperature through behavioral mechanisms, and that thermoregulation is mainly associated with substrate.

Iguanian species-richness in the Andes of boreal Patagonia: Evidence for an additional new Liolaemus lizard from Argentina lacking precloacal glands (Iguania, Liolaeminae)

Most Liolaemus lizard species are characterized by the presence of precloacal glands in males. Only a few taxa lack these sexual signal emitter structures. Phylogenetic evidence suggests that those species are restricted to the clades chiliensis and lineomaculatus. Within the first lineage, L. coeruleus, L. cristiani, L. flavipiceus, L. neuquensis and L. thermarum lack precloacal glands, which have been considered as members of the neuquensis group. Whereas, in the second one, L. periglacialis (= L. hatcheri), L. kolengh, L. lineomaculatus, and L. silvanae exhibit this characteristic. In the present study we provide the description of Liolaemus tregenzai, an additional new species lacking precloacal glands in both sexes. This new taxon, member of the chiliensis clade, is so far known from the Copahue Volcano, Neuquén Province of Argentina, in boreal Patagonia. Liolaemus tregenzai differs from the remaining species of this clade in having a unique combination of morphologic and chromatic traits, such as a large body size, olive or chest-nut dorsal ground colour, with dark brown or blackish pigment on the flanks, green-bluish with intense black pigment on the ventral surface, and evident sexual dichromatism. The ecology of this new lizard is also remarkably, occurring in Andean antarctandic forests, and being common near thawing snows. Phylogenetic relationships of this species with other members of the chiliensis clade and with the taxa recognized as members of the neuquensis group are still unknown.

Thermal ecology of a population of the lizard, Liolaemus pseudoanomalus in western Argentina

Abstract The thermal ecology of the lizard Liolaemus pseudoanomalus was studied at La Laja, Albardón Department, San Juan Province, Argentina. Data were collected every 10 days from August 2000 to August 2001 by randomly revisiting bushes and low flagstones across the study site. Each individual was captured by hand, and the cloacal (Tb), substrate (Ts) and air (Ts) temperatures were measured (to nearest 0.1°C) with a rapid reading Miller-Weber thermometer. Tb was not influenced by season, sex or age group. There was a significant positive linear association between Tb/Ta and Tb/Ts. Tb and SVL were not correlated. The average field temperature of the study species was similar to other Liolaemus in the same geographic province. It is concluded that the thermal strategy of the species was heliothermy and thigmothermy.

Chemoreception and the Assessment of Fighting Abilities in the Lizard Liolaemus monticola

AbstractWhen an individual faces the risk of a conflict, its ability to make ‘correct’ decisions is crucial to its fitness. Research on decision making has focused mainly on visual and acoustic signals, while chemical signals have received much less attention, despite their relevance for many species. Chemosignals can be detected in the absence of the signaller and, in the context of fighting risk, this property confers the advantage that the receiver can avoid agonistic interactions or, if they are unavoidable, that it can prepare itself for the conflict. I studied the behaviour of males of the lizard Liolaemus monticola in the laboratory when they were confronted with chemosignals of a potential opponent. During this ‘pre‐confrontation’ stage, I tested the following predictions: (1) lizards can derive precise information from chemosignals of conspecifics, and use this to respond with precision to the perceived risk and (2) the best predictor of the receiver behaviour, and therefore the best predictor of the risk involved in the fight, is the relative fighting ability of opponents. As a measure of fighting ability, I used body size. ‘Intruders’ were placed in the terrarium of unfamiliar ‘residents’ during the absence of the latter, and their behaviours were recorded. Simple regressions were performed between the different behavioural variables and with the body sizes of intruder and resident, and with the relative difference in body sizes of opponents. The latter was the best predictor of intruder behaviour: it was negatively correlated with behaviours associated with activity (i.e. motion time), chemoexploration (i.e. number of tongue flicks) and behaviours associated with social interactions (i.e. head bobs). These results suggest that males can process information from chemosignals and decisions made during the ‘pre‐confrontation’ stage are based on the assessment of the relative fighting abilities (i.e. relative body size) of opponents.

The role of ecological interactions on the physiological flexibility of lizards

Summary An organism's ability to adjust its physiological traits to changes in environmental conditions is central for its ecological success. However, the effect of ecological interactions on physiological flexibility has rarely been investigated. Here we carry out a factorial experiment to analyse how food limitation (a potential result of competition) and tail loss (a potential result of sub‐lethal predation) affect anatomical and physiological traits of the South American lizard Liolaemus nitidus. The size of several internal organs was affected by food availability. Small intestine mass increased with food consumption, allowing animals to keep constant digestibility at greater levels of digesta, which in turn permitted higher rates of food assimilation. Organs related to energy storage reached larger sizes in autotomized animals with high food availability, but tail regeneration rate after 3 weeks did not change with food availability. Metabolic rate was affected by tail loss, and animals regenerating their tail showed higher metabolic rates than tailed ones. Because this increase in metabolic rate was independent of internal organ mass, a local effect of tail regeneration process (e.g. cell proliferation) on metabolic rate is suggested. When anatomical and metabolic data are jointly considered it follows that lizards adopt different physiological strategies, changing both energetic inputs and expenditures. This fact illustrates the complex interplay between ecological factors and physiological flexibility, which ultimately determine an organism's fitness.

Triploidy and mosaicism in Liolaemus chiliensis (Sauria: Tropiduridae)

A remarkable diversity of ploidy, i.e., diploidy, triploidy, and diploid-triploid mosaicism, was found among the somatic and testicular cells in a natural population of the lizard Liolaemus chiliensis from central Chile. Intra pop ulation, intersexual, and intraindividual ploidy variation is reported. In contrast with other species of polyploid reptiles, 86% of L. chiliensis males were mosaics (2n/3n) and 14% were diploids; 33% of females were triploid, 57.1% were mosaics, and 9.5% were diploid. Among 21 specimens, no triploid males were found in this sample. In the mosaic males, the diploid and triploid spermatogonia both enter meiosis, producing both reduced and unreduced metaphase II spermatocytes, most of them euploids. We discuss the origin for this ploidy in this iguanid lizard.

The importance of phylogenetic scale in tests of Bergmann's and Rapoport's rules: lessons from a clade of South American lizards

We tested for the occurrence of Bergmann's rule, the pattern of increasing body size with latitude, and Rapoport's rule, the positive relationship between geographical range size and latitude, in 34 lineages of Liolaemus lizards that occupy arid regions of the Andean foothills. We tested the climatic-variability hypothesis (CVH) by examining the relationship between thermal tolerance breadth and distribution. Each of these analyses was performed varying the level of phylogenetic inclusiveness. Bergmann's rule and the CVH were supported, but Rapoport's rule was not. More variance in the data for Bergmann's rule and the CVH was explained using species belonging to the L. boulengeri series rather than all species, and inclusion of multiple outgroups tended to obscure these macroecological patterns. Evidence for Bergmann's rule and the predicted patterns from the CVH remained after application of phylogenetic comparative methods, indicating a greater role of ecological processes rather than phylogeny in shaping the current species distributions of these lizards.

Variability in the Assessment of Snake Predation Risk by Liolaemus Lizards

AbstractThe ability to assess and respond to predation risk is a strong selective force. Detection of predators is carried out by one or more sensory modalities, but the use of chemoreception has significant advantages. This study examines the chemosensorial assessment of snake predation risk and corresponding behaviours in different species and populations of Liolaemus lizards naturally exposed to different levels of snake predation pressure. The species studied were sympatric (Liolaemus lemniscatus), parapatric (L. nigroviridis) and allopatric (L. fitzgeraldi) to the saurophagous snake, Philodryas chamissonis. Additionally, two populations of L. lemniscatus from areas differing in snake densities were compared. Chemo‐assessment of predation risk was determined by comparing the number of tongue‐flicks (TF) and the behavioural responses of lizards submitted to three treatments (with semiochemicals of snake, conspecifics, and without semiochemicals – control). The results suggest that Liolaemus lizards can chemo‐assess snake predation risk, but this was modulated by the predation pressure experienced by lizards in their natural habitats. When exposed to snake semiochemicals, the sympatric prey showed less chemical exploratory behaviour (i.e. lower number of TF), a higher frequency of antipredator behaviours that would reduce its detection by a predator, and did not show the behaviour triggered by conspecific semiochemicals. The parapatric prey showed similar number of TF across different treatments, suggesting an absence of recognition of snake semiochemicals; however, it did show antipredatory behaviours when confronted with snake semiochemicals. The allopatric prey showed similar behaviour in all treatments. Both populations of the sympatric species, L. lemniscatus, showed a similar ability to detect predation risk when confronted with snake semiochemicals (i.e. similar number of TF), but antipredatory behaviours were diminished, and marking behaviours were present in the population subject to lower predation pressure. Relaxed predation pressure from a predator that releases and detects semiochemicals had similar consequences at species and population levels.

Large-scale patterns of signal evolution: an interspecific study of Liolaemus lizard headbob displays

Although many factors have been shown to influence the evolution of species recognition signals in a wide variety of taxa, it is difficult to draw general conclusions because of fundamental differences in the morphologies and ecologies of the animals considered. In this study, two morphologically and ecologically similar lizard genera ( Sceloporus and Liolaemus) are used to provide replicate examples of the evolution of a complex visual display. New data on the headbob displays of 16 Liolaemus species are presented. As in other taxa, phylogenetic analyses show that evolutionary changes in display structure have been rapid, leaving little, if any, phylogenetic information in the display structure. Evolutionary changes in display structure also do not appear to be closely associated with any major habitat characteristics. Despite this rapid evolution, Liolaemus lizards produce headbob displays that are remarkably simple in structure in comparison to those produced by Sceloporus, perhaps compensating for lower complexity by frequent use of other visual displays such as forelimb and tail waves.

Sexual dimorphism in Liolaemus occipitalis (Iguania, Tropiduridae)

The sexual dimorphism in size, morphology and color of the lizard Liolaemus occipitalis Boulenger, 1885 was studied. Thirty-two adult males and twenty-eight adult females were sampled from a population in the Jardim do Éden beach, near Tramandaí, Rio Grande do Sul, Brazil. Size related sexual dimorphism occurred in all compared body dimensions. The largest female was 59.6 mm in snout-vent length, and the largest male was 69.3 mm. Males and females also presented differences in ventral and dorsal color pattern, and in the presence of pre-cloacal pores. The results suggest that, in Liolaemus occipitalis, sexual dimorphism in size is determined by sexual selection, competition between males and by the high energetic cost for females a few months after hatching.

Negative impacts of a vertebrate predator on insect pollinator visitation and seed output in Chuquiraga oppositifolia, a high Andean shrub.

Studies on plant-pollinator interactions have largely neglected the potential negative effects of the predators of pollinators on seed output, even though anti-predatory behaviour of pollinators may affect visitation patterns, pollen transfer, and therefore potentially, plant reproductive output. We tested the hypothesis that the presence of lizards and insectivorous birds, by reducing pollinator visitation, can have significant negative effects on seed output in the insect-pollinated, genetically self-incompatible lower alpine Andean shrub, Chuquiraga oppositifolia (Asteraceae). The lower alpine belt supports a high density of territorial Liolaemus (Tropiduridae) lizards and low shrubs interspersed among rocks of varying sizes, the latter inhabited by lizards and commonly used by flycatchers Muscisaxicola (Tyrannidae) as perching sites. In a 2x2 factorial predator-exclusion experiment, visitation rates of the most frequent pollinators of C. oppositifolia (the satyrid butterfly Cosmosatyrus chilensis and the syrphid fly Scaeva melanostoma), the duration of pollinator visits, and seed output, were 2-4 times greater when lizards were excluded, while birds had no effect. In a natural experiment, visits by S. melanostoma were 9 times shorter, and pollinator visitation rates of C. chilensis and S. melanostoma, and C. oppositifolia seed output were 2-3 times lower on shrubs growing adjacent to lizard-occupied rocks compared to those growing distant from rocks. Our results, verified for additional Andean sites, suggest that lizard predators can alter the behaviour of pollinators and elicit strong top-down indirect negative effects on seed output. Such effects may be especially important in high alpine plant communities, where pollinator activity can be low and erratic, and pollen limitation has been reported.

Age and season affect chemical discrimination of Liolaemus bellii own space.

We explored chemical discrimination of own vs. novel space by different age classes (neonates, juveniles, and adults) of the lizard Liolaemus bellii, during pre- and post-hibernation seasons. We recorded the number of tongue flicks (TF) lizards produced during 10 min in their own or a novel enclosure. Age class and season affected chemical discrimination. Only adults and neonates discriminated their own space, albeit using different strategies: while adults made fewer TF in their own enclosure, neonates made more TF in their own enclosure. This difference was interpreted in terms of different requirements for discrimination of individuals during their lives. Increased chemical exploration by juveniles and adults at the onset of the post-hibernation season was associated with food-searching and reproductive behaviors.

Chemical composition of precloacal secretions of two Liolaemus fabiani populations: are they different?

The chemical composition of secretions of precloacal pores from two populations of the lizard Liolaemus fabiani (Puilar and Punta-Brava) were compared. This is an endemic species from the Atacama Salt Flat (26 degrees 46'S 68 degrees 14'W; 2400 m) in northern Chile, restricted to the internal lakes of the salt flat. Interpopulational differences in the chemical composition of the secretions were expected considering that populations have genetic differences and are subject to different thermal conditions. By using GC-MS, a total of 44 compounds were found belonging to three categories: n-alkanes, long-chain carboxylic acids, and steroids. Six compounds were found in all the individuals studied: tetradecanoic, pentadecanoic, hexadecanoic, hexadecenoic, octadecanoic, and octadecenoic acids. The secretions of both populations had similar types and proportions of the different compounds, except for cholesterol and hexanoic acid, which were more abundant in the Puilar population. These differences can be ascribed to the different environmental conditions to which populations are subjected. The adaptive meaning of these differences is discussed.

Interactions between Males of the Lizard Liolaemus tenuis: Roles of Familiarity and Memory

For territorial organisms, recognition of familiar individuals can reduce the frequency and intensity of aggressive encounters (‘dear enemy’ phenomenon), stabilize social systems, and reduce the cost of territory maintenance. Here, we investigated the behavioural events displayed during contests between familiar and unfamiliar individuals in the lizard Liolaemus tenuis (Liolaemidae), a species in which males are territorial. The behaviours recorded were attack, warning, evasion, and submission, and the latencies to the first aggressive (attack or warning) behaviour. Additionally, we assessed the ability of individuals to remember a familiar conspecific after a period without social interaction. Individual males reduced and delayed aggressive behaviour directed towards socially familiar individuals compared with unfamiliar ones. These results suggest that males distinguished between familiar and unfamiliar conspecific males and are in agreement with the ‘dear enemy’ phenomenon. Other behaviours were similar in the contests between familiar and unfamiliar individuals. Recognition of familiar conspecifics was lost after 20 d without social interactions. This may be relevant for interactions with floater males or with neighbours that lose their territory and subsequently attempt to fight for their ex-neighbour's territory.

Interplay between pregnancy and physiological thermoregulation in Liolaemus lizards

In squamate reptiles the effects of pregnancy on physiological thermoregulation, such as thermal tolerances and rates of heat exchange, are practically unknown. This is remarkable since pregnancy involves changes in body vascularization and may consequently affect heat exchange. We studied the effects of pregnancy on physiological thermoregulation in four oviparous Liolaemus species from central Chile. Results indicated that pregnancy did not affect most of the variables measured. In two species, however, pregnant females had slower heating rates than non-pregnant individuals, suggesting a capacity to control the egg thermal environment. On the other hand, in contrast to other small lizards, in Liolaemus heating, but not cooling, rates may have an adaptive value as a thermoregulatory mechanism. Cooling rates and thermal minimal tolerances seem to evolve less readily.

Parasite loads and altitudinal distribution of Liolaemus lizards in the central Chilean Andes

Este estudio compara las distribuciones de diez especies de lagartijas Liolaemus en los Andes de Chile central, con las distribuciones de cuatro tipos de parasitos: Plasmodium causantes de malaria, nematodos intestinales, garrapatas y acaros. Quisimos verificar si los numeros de parasitos pudieran ser un factor determinante de los limites de distribucion de las lagartijas. Encontramos que no habia evidencia de infestacion por malaria en las lagartijas; que las garrapatas estaban casi ausentes; que los numeros de acaros mas a menudo decrecian que aumentaban en los limites distribucionales de las lagartijas; y que los nematodos intestinales confinados a las lagartijas herbivoras en nuestra muestra bien podian ser beneficiosos antes que daninos. Mas bien que parasitismo, otras interacciones bioticas (e.g., depredacion o competencia) son candidatos mas probables como factores que influyen las distribuciones altitudinales de las lagartijas, ademas de caracteristicas abioticas tales como la disponibilidad de microhabitats y los factores termicos