The relationship between morphology, escape behaviour and microhabitat occupation in the lizard clade Liolaemus (Iguanidae: Tropidurinae: Liolaemini)

Phenotypic differences among species are known to have functional consequences that in turn allow species to use different habitats. However, the role of behaviour in this ecomorphological paradigm is not well defined. We investigated the relationship between morphology, ecology and escape behaviour among 25 species of the lizard clade Liolaemus in a phylogenetic framework. We demonstrate that the relationship between morphology and characteristics of habitat structure shows little or no association, consistent with a previous study on this group. However, a significant relationship was found between morphology and escape behaviour with the distance a lizard moved from a potential predator correlated with body width, axilla-groin length, and pelvis width. A significant relationship between escape behaviour and habitat structure occupation was found; lizards that occupied tree trunks and open ground ran longer distances from predators and were found greater distances from shelter. Behavioural strategies used by these lizards in open habitats appear to have made unnecessary the evolution of limb morphology that has occurred in other lizards from other clades that are found in open settings. Understanding differences in patterns of ecomorphological relationships among clades is an important component for studying adaptive diversification.     

Molecular evidence for a species complex in the patagonian lizard Liolaemus bibronii and phylogeography of the closely related Liolaemus gracilis (Squamata: Liolaemini)

The lizard genus Liolaemus is endemic to temperate South America and includes 190 species. Liolaemus bibronii has a large geographic distribution and inhabits a great diversity of habitats, including the Monte, Steppe, and high Andean grassland environments. Liolaemus gracilis has a similar body size and shape to L. bibronii; the two are parapatrically distributed, and L. gracilis is also widely distributed. Here we use the mtDNA cytb sequence data of these two species to investigate lizard phylogeographic patterns in southern South America. L. bibronii is paraphyletic with respect to L. gracilis, Liolaemus ramirezae, Liolaemus robertmertensi and Liolaemus saxatilis; it is composed of many genetically different allopatric haploclades, some of which are reciprocally monophyletic. We also found evidence for introgression between L. bibronii and L. gracilis in the same area that introgression was hypothesized in the Liolaemus darwinii complex. We discuss the distribution of the major haploclades with inferences of their population histories, the concordance of these clades' distributions and histories with other lizard complexes studied with the same markers and methods, and taxonomic implications of these results.     

Phylogeography between valleys and mountains: the history of populations of Liolaemus koslowskyi (Squamata,Liolaemini)

The lizard genus Liolaemus is endemic to temperate South America and includes approximately 200 species. Liolaemus koslowskyi occurs in north‐western Argentina, where it is confined to a system of interior basins and valleys. This topographically complex region is now viewed as different enough that it has been suggested for recognition as a separate zoogeographical region: The Monte Desert of Mountains and Isolated Valleys. Here we use the mtDNA cytochrome b sequence data to investigate the phylogeographical pattern of L. koslowskyi and its relationships with other species of the darwinii group. Liolaemus koslowskyi is monophyletic with respect to all the species of the darwinii group included in this analysis. Three main clades were recovered within L. koslowskyi and we hypothesized that at least one of these, which shows 7% genetic divergence, is a candidate species. We discuss the phylogeographical patterns in association with the geological history of the region. The highly structured L. koslowskyi clade suggests that it has a relatively ancient history in a topographically rich, terrestrial archipelago of habitat and tectonic islands that are themselves relictual mountains and valleys.     

Relationships among morphology, clinging performance and habitat use in Liolaemini lizards

The central tenet of ecomorphological theory holds that different ecological requirements lead to different organismal designs (morphology). Here, we studied the relationships between performance (interlocking grasping) and forelimb morphological traits in species of lizards that exploit different structural habitats in a phylogenetic context. The performance (measured by the maximum force of clinging to substrate) was measured on different substrate types. After phylogenetically informed analyses, we found that arboreal and saxicolous species showed stronger resistance to mechanical traction in all substrates when compared to generalists and sand dweller lizards. These species showed a positive relationship between forelimb dimensions (humerus length and length of claw of toe 5) and maximum force exerted, on the contrary, hand width, claw height (CH) of digits III and IV and claw length of toe 4 showed a negative relationship. In addition, we observed a partial positive correlation between CH and maximal cling force on rough surfaces, but not on smooth surfaces.     

Altitudinal variation of the thermal biology and running performance in the lizard Podarcis tiliguerta

Summary We studied, in the field and laboratory, aspects of the thermal biology in two populations of the lizard Podarcis tiliguerta along a 1450 m altitudinal gradient. Body temperatures (T_b) at high altitudes average lower, are more variable, but are more elevated above environmental temperatures than at sea level. Lizards partially reduced the impact of altitudinal changes in thermal loads through presumable subtle behavioural adjustments. A comparison of the thermal preferences in the laboratory, the maximal operative temperatures predicted from a biophysical model, and the activity T_b's at both sites, indicates that the main response to changing environmental conditions is an active shift in thermoregulatory set points. Integration of field T_b's and laboratory data on temperature specific sprint speeds, predicts that the mountainous lizards experience reduced running abilities that are especially acute in the early morning. Despite this impairment of running performance, the thermal sensitivity of running speed has not evolved to match the T_b's experienced by both populations. This result supports the view that the thermal physiology of this lizard is evolutionarily conservative, but the lack of information on the relation between running performance and fitness components impedes rejection of alternative hypotheses.     

Ontogenetic and sexual differences of thermal biology and locomotor performance in a lacertid lizard,Eremias multiocellata

A viviparous lizard, Eremias multiocellata, was used to investigate the possible sexual and ontogenetic effects on selected body temperature, thermal tolerance range and the thermal dependence of locomotor performance. We show that adults are sexually dimorphic and males have larger bodies and heads than females. Adults selected higher body temperatures (34.5 vs. 32.4 °C) and could tolerate a broader range of body temperatures (8.1–46.8 vs. 9.1–43.1 °C) than juveniles. The sprint speed and maximum sprint distance increased with temperature from 21 °C to 33 °C, but decreased at 36 °C and 39 °C in both juveniles and adults. Adults ran faster and longer than juveniles at each tested temperature. Adult locomotor performance was not correlated with snout–vent length (SVL) or sex, and sprint speed was positively correlated with hindlimb length. Juvenile locomotor performance was positively correlated with both SVL and hindlimb length. The ontogenetic variation in selected body temperature, thermal tolerance and locomotor performance in E. multiocellata suggests that the effects of morphology on temperature selection and locomotor performance vary at different ontogenetic stages.     

Chemical recognition of conspecifics in a neotropical lizard, <Emphasis Type="Italic">Liolaemus pacha</Emphasis> (Iguania: Liolaemidae): relation to visual displays,season and sex

Chemical cues play an important role in sexual recognition in several lizard species. Here, we investigated whether the neotropical lizard, Liolaemus pacha (Iguania: Liolaemidae) can discriminate between chemical information obtained from males or females. In addition, we also considered the effect of season (reproductive vs. post-reproductive) and the sex of the tested individual. We experimentally tested scent discrimination, using a terrarium previously occupied by a male, a female, and an untreated terrarium as control as sources of different chemical scents. We counted the number of tongue flicks, a measure of chemical exploratory behavior, and the visual displays triggered by these scents for 10 min. Males performed significantly more tongue flicks when female scent was present than when male and control scents were present, indicating sexual recognition. However, females did not show a significant difference in those same conditions, indicating a lack of sexual recognition. For visual displays, males showed significantly higher rates to female and male scents than to control, whereas females did not show any difference. During the reproductive season, the number of tongue flicks and visual displays were higher than during the post-reproductive season. Our results suggest that for male L. pacha, chemical cues play an important role in mate recognition. We discuss the apparent lack of recognition in females. We suggest that the observed seasonal behavioral differences might be associated with physiological changes related mainly to reproduction.     

Histochemical detection of sugar residues in lizard teeth (Liolaemus gravenhorsti): a lectin-binding study

The structural diversity of the many oligosaccharide chains of surface glycoconjugates renders them likely candidates for modulators of cell-interactions, cellular movements, differentiation, and cellular recognition. A selection of different lectins was used to investigate the appearance of cellular distribution and changes in sugar residues during tooth development in the polyphyodont lizard, Liolaemus gravenhorsti. Lectins from three groups were used: (1) N-acetylgalactosamine specificity: BS-1, PNA, RCA-120; (2) N-acetylglucosamine specificity: ECA; and (3) fucose specificity: UEA 1 and LTA.. Digital images were processed using Scion Image. Grayscale graphics in each image were obtained. The lectins used showed a strong, wide distribution of the L-fucose and N-acetylgalactosamine at the cell surface and in the cytoplasm of multinucleate odontoclast cell, while mononuclear odontoclast cells showed no binding, suggesting some roles that the residues sugar might play in the resorption of dentine or with multinucleation of odontoclast after the attachment to the dentine surface in this polyphyodont species. Further studies must be planned to determine the specific identities of these glycoconjugates,and to elucidate the roles played by these sugar residues in the complex processes related to odontogenesis in polyphyodont species.     

Seasonal and geographic variation in thermal biology of the lizard Microlophus atacamensis (Squamata: Tropiduridae)

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We studied physiological thermal adaptation in the lizard Microlophus atacamensis along a latitudinal range.     

Cytological characterization of the germinal line during testicular differentiation in the lizard Liolaemus gravenhorsti (gray)

The gross morphology, histology, and ultrastructure of Liolaemus gravenhorsti gonads prior to and after differntiation are described. Special emphasis has been given to characterization and changes of the germ cell line throughout intrauterine development and 3 days postpartum. During the pregonadal stage, the primordial germ cell migrates toward gonadal rudiments by way of the mesenchyme. These cells can easily be identified by their great size, voluminous and lobulated nucleus, great quantities of yolk platelets, microtubules, and numerous lipid inclusions. In the undifferentiated gonad, the germ cells (type 1 gonocytes) have an ovoid or spherical shape and autodigestion of yolk platelets, great development of Golgi complex, and mitochondrial aggregation, though fewer liposomes, pseudopodes, and microtubules were noted. Concomitantly with the beginning of mitosis, a third type of germ cell appears, the type 2 gonocytes, which are smaller, with poorly defined membranous systems in various degrees of involution. The seminiferous cords are organized when somatic cells of the medullar portion of the gonad surround type 1 gonocytes. Germinal cells are centrally localized in the cords. Near birth many gonocytes migrate toward the basal lamina of cords and differentiate into spherical prespermatogonia, with few organoids. Sertoli cells eparate them from the basal lamina. In advanced pregnancy, Leyding cells become numerous with morphology typical of androgen-producing cells.     

Early stages of divergence: phylogeography, climate modeling, and morphological differentiation in the South American lizard Liolaemus petrophilus (Squamata: Liolaemidae)

This study examines the phylogeographic structure within the Patagonian lizard Liolaemus petrophilus and tests for patterns of between-clade morphological divergence and sexual dimorphism, as well as demographic and niche changes associated with Pleistocene climate changes. We inferred intraspecific relationships, tested hypotheses for historical patterns of population expansion, and incorporated ecological niche modeling (ENM) with standard morphological and geometric morphometric analyses to examine between-clade divergence as indirect evidence for adaptation to different niches. The two inferred haploclades diverged during the early Pleistocene with the Southern clade depicting the genetic signature of a recent population increase associated with expanding niche envelope, whereas the Northern clade shows stable populations in a shrinking niche envelope. The combination of molecular evidence for postisolation demographic change and ENM, suggest that the two haploclades have responded differently to Pleistocene climatic events.     

Evidence of hybridization in the Argentinean lizards Liolaemus gracilis and Liolaemus bibronii (IGUANIA: LIOLAEMINI): an integrative approach based on genes and morphology

The lizard genus Liolaemus is endemic to temperate South America and includes more than 225 species. Liolaemus gracilis and L. bibronii are closely related species that have large and overlapping geographic distributions, and the objective of this work is to further investigate the L. bibronii–L. gracilis mtDNA paraphyletic pattern previously detected, using an integrative approach, based on mtDNA, nuclear DNA and morphological characters. We identified eight morphological L. bibronii introgressed with L. gracilis mtDNAs, and the reciprocal for one L. gracilis, from six localities in the region of sympatry overlap. The morphological identity of these introgressed individuals was confirmed by diagnostic nuclear markers, and this represents the first well-documented case of interspecific hybridization in the lizard genus Liolaemus. Of the three most likely hypotheses for these observed patterns, we suggest that asymmetrical mtDNA introgression as a result of recent or ongoing hybridization between L. bibronii and L. gracilis is the most likely. This may be due to size selection by L. gracilis female preference for the larger L. bibroni males in sympatry, but this requires experimental confirmation.     

Thermal biology of the southernmost lizards in the world: Liolaemus sarmientoi and Liolaemus magellanicus from Patagonia,Argentina

We determined the efficiency of thermoregulation by the southernmost liolaemids Liolaemus sarmientoi and L. magellanicus from Patagonia, Argentina (51°S), by measuring body (T_b), microenvironmental, and operative temperatures in the field, and preferred body temperatures in the laboratory (T_pref). L. sarmientoi was found to be a poor thermoregulator, whereas L. magellanicus was deemed to be a constrained thermoconformer. Among all known species of Liolaemus, L. sarmientoi and L. magellanicus had the lowest T_b's when tested in the field; however, their T_pref's were similar to other liolaemids. These data suggest that these southernmost liolaemid species have not evolved appropriate thermoregulatory behaviors or made adequate physiological adaptations to face the extreme thermal challenges of their environment.     

A molecular phylogeny of the lizard genus Phymaturus (Squamata,Liolaemini): Implications for species diversity and historical biogeography of southern South America

The lizard genus Phymaturus is widely distributed in Argentina and along the eastern edge of Chile between 25° and 45° south. We sampled 27 of the 38 currently recognized species plus 22 candidate species using two mitochondrial genes (cytb and 12S), four protein coding nuclear genes and seven anonymous nuclear loci, and present the first comprehensive molecular phylogenetic hypothesis for the clade. We recovered two large clades (the palluma or northern group and patagonicus or southern group) previously recognized on the basis of morphological and mitochondrial sequence evidence, and compared results obtained from concatenated-gene analyses with results of a coalescent-based species-tree approach (BEST). With both methods we identified four main clades within the palluma group (mallimaccii, roigorum, verdugo, and vociferator) and five main clades within the patagonicus group (calcogaster, indistinctus, payuniae, somuncurensis, and spurcus). We found several instances of non-monophyly with cytb and cases of incongruence between mitochondrial vs nuclear data for which we discuss alternative hypotheses. Although with lower support values, combined BEST results are more congruent with concatenated nuclear data than with combined concatenated analyses, suggesting that BEST is less influenced by demographic processes than combined concatenated analyses. We discuss the taxonomic, biogeographic and conservation implications of these results and how the future integration of phylogeographic and morphological approaches will allow the further testing of demographic and biogeographic hypotheses.     

Performance and thermal sensitivity of the southernmost lizards in the world, Liolaemus sarmientoi and Liolaemus magellanicus

Locomotor activity performance of reptiles is largely temperature dependent and, in harsh environments with short activity periods during the day and throughout the year, plays a vital role in the fitness of the species. This particular study focuses on the performance and the thermal sensitivity for running, at different body temperatures, of the two southernmost species of lizards in the world, Liolaemus sarmientoi and Liolaemus magellanicus, studied at two locations in the south of Santa Cruz province, Argentina (51°S, 70°W and 50°S, 72°W; 133 m asl). The speed of sprint and long runs was measured in the field to determine the physiological performance of lizards at different air temperatures. In both species speed increases with the temperature, and they reach the highest performance at high temperatures. The difference between activity and thermal optima suggests that L. magellanicus has colonized its actual environment recently, and that it has not had enough time for its physiological mechanisms to evolve and achieve a maximum performance at the cold temperatures they have to tolerate at present. In contrast, L. sarmientoi achieved a high performance over a wider range of temperatures that included temperatures lower than the preferred temperatures in the lab, which they can generally find in their environment.     

A new species of Liolaemus related to L. nigroviridis from the Andean highlands of Central Chile (Iguania,Liolaemidae)

The Liolaemus nigroviridis group is a clade of highland lizards endemic to Chile. These species are distributed from northern to central Chile, and currently there are no cases of sympatric distribution. This study describes a new species, Liolaemus uniformis sp. n., from this group, and provides a detailed morphological characterization and mitochondrial phylogeny using cytochrome-b. Liolaemus uniformis was found in sympatry with Liolaemus nigroviridis but noticeably differed in size, scalation, and markedly in the color pattern, without sexual dichromatism. This new species has probably been confused with Liolaemus monticola and Liolaemus bellii, both of which do not belong to the nigroviridis group. The taxonomic issues of this group that remain uncertain are also discussed.     

Ectoparasitism by Eutrombicula alfreddugesi larvae (Acari: Trombiculidae) on Liolaemus tenuis lizard in a Chilean fragmented temperate forest

We compared parasite load (prevalence and mean intensity) of Eutrombicula alfreddugesi larvae on the lizard Liolaemus tenuis sampled during January 2006 and 2007 from the interior and edges of large forest tracts in the coastal Maulino Forest (35 degrees 59'S, 72 degrees 41'W) and from nearby forest fragments (1.5-20 ha). All lizards were parasitized by chiggers regardless of location (prevalence, 100%); however, mean intensity of infestation was significantly lower at forest fragment edges compared with either large forest interiors or forest edges. We attribute differences in mean intensity to differences in microclimate among localities; maximum air temperature was significantly higher and relative humidity significantly lower in fragment edges compared with either large forest tract interior or edges.