Robert E. Espinoza

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 Bergmanns rule, the pattern of increasing body size with latitude, and Rapoports 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. Bergmanns rule and the CVH were supported, but Rapoports rule was not. More variance in the data for Bergmanns 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 Bergmanns 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.

Two New Cryptic Species of Liolaemus (Iguania: Tropiduridae) from Northwestern Argentina: Resolution of the Purported Reproductive Bimodality of Liolaemus alticolor

The Liolaemus alticolor group (Iguania: Tropiduridae) currently includes two or three species of morphologically similar, small-bodied lizards distributed from southern Peru and Bolivia to northern Argentina and Chile. Recently, a few populations of L. alticolor from northwestern Argentina were reported to be reproductively bimodal-having both oviparous and viviparous females at the same locality. We reexamined lizards from these putatively bimodal populations and found evidence that these populations include two sympatric yet distinct species-one oviparous, the other viviparous. These species can also be distinguished from L. alticolor sensu stricto from the type locality (Tiahuanaco, Bolivia). Here we describe the two new species, L. ramirezae and L. pagaburoi, from the province of Tucuman, Argentina. Liolaemus ramirezae differs from L. alticolor in having distinct neck folds, precloacal pores in females, and an oviparous reproductive mode, and in lacking both spots on the throat in males and a vertebral line. Liolaemus pagaburoi differs from L. alticolor in having distinct paravertebral markings, slender dorsal stripes, and more rugose head scales. Recognition of these new species as distinct resolves the paradox of reproductive bimodality in L. alticolor. Interestingly, both of the new species appear to be microhabitat specialists that associate with a single species of plant in their respective habitats. As predicted by the cold-climate hypothesis, the oviparous species is distributed in a warmer climate than is the viviparous species. El grupo Liolaemus alticolor (Iguania: Tropiduridae) actualmente incluye unas dos a tres especies morf6logicamente similares. Se trata de lagartos pequenos distribuidos desde el sur de Peru y Bolivia hasta el norte de Argentina y Chile. Recientemente, unas pocas poblaciones de L. alticolor del noroeste de Argentina fueron reportadas por exhibir bimodalidad reproductiva, es decir, contar tanto con hembras oviparas como hembras viviparas en la misma localidad. En este trabajo se revisaron esas poblaciones y encontramos evidencia que las mismas incluyen dos especies simpatricas, una vivipara y la otra ovipara. Estas especies se diferencian asimismo de L. alticolor sensu stricto de la localidad tipo (Tiahuanaco, Bolivia). Aqui

Lizards, Lipids, and Dietary Links to Animal Function

Our experiments were designed to test the hypotheses that dietary lipids can affect whole‐animal physiological processes in a manner concordant with changes in the fluidity of cell membranes. We measured (1) the lipid composition of five tissues, (2) body temperatures selected in a thermal gradient (Tsel), (3) the body temperature at which the righting reflex was lost (critical thermal minimal [CTMin]), and (4) resting metabolic rate (RMR) at three body temperatures in desert iguanas (Dipsosaurus dorsalis) fed diets enriched with either saturated or unsaturated fatty acids. The composition of lipids in tissues of the lizards generally reflected the lipids in their diets, but the particular classes and ratios of fatty acids varied among sampled organs, indicating the conservative nature of some tissues (e.g., brain) relative to others (e.g., depot fat). Lizards fed the diet enriched with saturated fatty acids selected warmer nighttime body temperatures than did lizards fed a diet enriched with unsaturated fatty acids. This difference is concordant with the hypothesis that the composition of dietary fats influences membrane fluidity and that ectotherms may compensate for such changes in fluidity by selecting different body temperatures. The CTMin of the two treatment groups was indistinguishable. This may reflect the conservatism of some tissues (e.g., brain) irrespective of diet treatment. The RMR of the saturated treatment group nearly doubled between 30° and 40°C. Here, some discrete membrane domains in the lizards fed the saturated diet may have been in a more‐ordered phase at 30°C and then transformed to a less‐ordered phase at 40°C. In contrast, the RMR of the unsaturated treatment group exhibited temperature independence in metabolic rate from 30° to 40°C. Perhaps the unsaturated diet resulted in membranes that developed a higher degree of disorder (i.e., a certain phase) at a lower temperature than were membranes of lizards fed the saturated diet. Our study demonstrates links between dietary fats and whole‐animal physiology; however, the mechanistic basis of these links, and the general knowledge of lipid metabolism in squamate reptiles, remain poorly understood and warrant further study.

Two New Liolaemus from the Puna Region of Argentina and Chile: Further Resolution of Purported Reproductive Bimodality in Liolaemus alticolor (Iguania: Liolaemidae)

Abstract We provide descriptions for two new cryptic species belonging to the Liolaemus alticolor group from northern Argentina and northeastern Chile. The new species were previously considered conspecific with either Liolaemus walkeri in northeastern Chile or L. alticolor in northwestern Argentina and adjacent Chile. However, the new species differ from these taxa, and all other members of the alticolor group, in a number of characteristics. Liolaemus chaltin n. sp. differs from L. alticolor from the type locality (Tiahuanaco, Bolivia) in the following ways: this new species has a larger body size; a fragmented vertebral stripe; and a pigmented subocular (white in L. alticolor), and is one of just three members of the alticolor group that is oviparous. Liolaemus puna n. sp. differs from all other members of the alticolor group in that male L. puna lack paravertebral markings and dorsolateral and vertebral stripes. Females, however, are similar to other members of the alticolor group but can be distinguished from them by several meristic characters. Liolaemus puna is widely distributed throughout the high-elevation (3680–4400 m) Puna regions (a flat or gently sloping steppe dominated by perennial bunch grasses and small shrubs) in northwestern Argentina and northeastern Chile. Liolaemus chaltin is known only from the Puna of central Jujuy Province, Argentina (3400–3750 m). Based on examinations of the type series of L. alticolor and L. walkeri, we determined that virtually all northern Chilean populations of Liolaemus previously considered to belong to either of these two species should be assigned to L. puna. Thus, the range of L. alticolor is restricted to Bolivia and southern Perú, and the range of L. walkeri is restricted to central and southern Andean Perú. Liolaemus chaltin is oviparous, and L. puna is viviparous, and because both are morphologically similar to L. alticolor, some investigators have suggested that some populations of L. alticolor may be reproductive bimodal. Our studies, however, indicate that these populations represent sympatric populations of the cryptic species described herein. A diagnostic key is provided for the currently recognized members of the alticolor group.

A New Phymaturus (Iguania: Liolaemidae) from the Southern Extreme of the Argentine Puna

We describe a new species of Phymaturus from the Sierra La Invernada of San Juan Province, Argentina. The new species shares the apomorphies of the P. palluma group including a fragmented subocular, square nonimbricate superciliaries, rugose and strongly mucronate dorsal caudals, and a midvertebral band of enlarged scales. Within the P. palluma group, the new species can be assigned to the Puna clade, with which it shares a dorsal pattern of small, dispersed brown spots and lack of black reticulations. The new species differs from other members of the Puna clade in several aspects of squamation and body pattern and color. Most notably, the new Phymaturus has a conspicuous yellow scapular spot, lacks a vertebral stripe, and has incomplete dark pigmentation over the dorsal neck. The new species is known only from the region of the type locality, the southernmost (and geographically isolated) extent of the Puna phytogeographic province, where it occurs at high elevations (>3100 m). We provide information on aspects of the natural history, diet, thermal biology, and apparent parental care exhibited by females of the new species. Describimos una nueva especie de Phymaturus de la Sierra La Invernada de la provincia de San Juan, Argentina. La nueva especie comparte las apomorfías del grupo P. palluma incluyendo una subocular fragmentada, superciliares cuadrangulares no imbricadas, escamas caudales dorsales rugosas y muy mucronadas y una banda mediovertebral de escamas agrandadas. Dentro del grupo P. palluma, la nueva especie se asigna al clado Puna, con el que comparte un patrón dorsal de pequeñas y dispersas manchas marrones y la falta de reticulaciones en negro. La nueva especie se diferencia de otros miembros del clado Puna en varios aspectos de la escamación y el patrón de cuerpo y color. Lo más notable en el nuevo Phymaturus es una mancha escapular amarilla, carece de una franja vertebral, y tiene pigmentación oscura incompleta sobre el dorso del cuello. La nueva especie es conocida sólo de la región de la localidad tipo, la más meridional (y geográficamente aislada) extensión de la provincia fitogeográfica de la Puna, donde se encuentra a gran elevación (>3100 m). Proveemos de información sobre aspectos de la historia natural, la dieta, la biología térmica, y el aparente cuidado parental exhibido por hembras de la nueva especie.

Diet quality does not affect resting metabolic rate or body temperatures selected by an herbivorous lizard

Abstract Diet quality can influence many aspects of digestion, but the links between diet quality and resting metabolism are poorly understood. In nature, it might be beneficial to reduce energy expenditure when only poor quality diets are available. Alternatively, animals might increase the processing capacity of the gut to more thoroughly extract energy. If maintaining the processing capacity of the gut is energetically expensive, then increasing gut size or function might result in higher resting metabolism. In ectotherms, most digestive functions are temperature dependent, thus another strategy to maintain energy balance might be to alter selected body temperatures. We tested whether differing concentrations of dietary fiber affected the resting metabolic rate or body temperatures selected by chuckwallas (Sauromalus obesus) – lizards that naturally experience marked variation in dietary fiber. Resting metabolic rates measured at two temperatures and over three time intervals did not differ between groups of lizards force-fed low- (30% neutral-detergent fiber; NDF) and high-fiber (45% NDF) diets, nor did these diet differences influence body temperatures selected in a thermal gradient. We conclude that ecologically relevant differences in diet quality may have negligible effects on resting metabolic rates and body temperatures selected by chuckwallas.

Responses to prey and plant chemicals by three iguanian lizards: relationship to plants in the diet

We examined responses of three iguanian lizards, the phrynosomatid Sceloporus poinsettii and the tropidurids Tropidurus hispidus and Phymaturus punae , to prey chemicals and plant chemicals. When chemical stimuli were presented on cotton swabs or on ceramic tiles, neither S. poinsettii nor T. hispidus discriminated among prey, plant, and control stimuli. In contrast, an individual of P. punae discriminated both prey and plant chemicals from control stimuli in swab tests, typically biting swabs bearing prey or plant cues. These findings are consistent with the hypothesis that plant chemical discrimination evolves in herbivorous iguanians such as P. punae . Sceloporus poinsettii , which appears to be entirely insectivorous at some times, but eats substantial quantities of flowers at others, did not discriminate among the stimuli. Because all previously tested herbivores and omnivores responded strongly to prey and plant chemicals, the absence of such discriminations by S. poinsettii raises questions about the degree and regularity of herbivory that may be required for plant chemical discrimination to evolve. The results extend the absence of prey chemical discrimination in ambush foragers to T. hispidus .

Herbivory in Liolaemus poecilochromus, a Small, Cold-Climate Lizard from the Andes of Argentina

Herbivory is generally thought to be restricted to reptiles with large body sizes that live in warm climates. We show that Liolaemus poecilochromus is primarily herbivorous (>80% plants in diet) even as juveniles, making them the smallest herbivorous reptile known. We detected relatively few differences in diet between the sexes, despite male-biased sexual dimorphism in head and body size. Adults consumed more mites and flowers than juveniles, and we detected a weak ontogenetic shift from omnivory to herbivory that is attributable to the lower volumetric consumption of plants by juvenile males. We discuss the abiotic and biotic conditions that likely selected for herbivory in this and other small-bodied, high-elevation Liolaemus. Herbivoría en general se cree que se limita a los reptiles con cuerpos grandes que viven en climas cálidos. Mostramos que Liolaemus poecilochromus es principalmente herbívora (>80% de plantas en la dieta) incluso los juveniles, convirtiéndolo por esto en el reptil herbívoro más pequeño conocido. Asimismo, detectamos pocas diferencias en la dieta entre los sexos, a pesar del dimorfismo sexual a favor de los machos en el tamaño de la cabeza y el cuerpo. Los adultos consumen más ácaros y flores que los juveniles, por otro lado se detectó un cambio ontogenético débil de omnivoria a herbivoría en los machos juveniles, debido a su bajo consumo de plantas. Discutimos las condiciones abióticas y bióticas que probablemente favorecieron la herbivoría en este y otros Liolaemus de cuerpo pequeño y alta elevación.

The First Parthenogenetic Pleurodont Iguanian: A New All-female Liolaemus (Squamata: Liolaemidae) from Western Argentina

Vertebrate taxa with entirely unisexual populations are composed of females that reproduce without fertilization and are generally of hybrid origin. At least 23 vertebrate families have unisexual lineages. Within squamate reptiles, >40 uniparental species have been described from five major lineages: acrodont iguanians, Gekkota, Serpentes, Scincomorpha, and Varanidae. Pleurodont iguanians include >1100 species, all of which have gonochoristic reproduction. Here we report the discovery of a new unisexual lizard from the liolaemid genus Liolaemus, a species-rich (∼260 species) clade distributed over most of southern South American. The new species, Liolaemus parthenos, is the only known all-female triploid pleurodont iguanian. The structural chromosome heteromorphisms of the karyotypes support the hypothesis that L. parthenos is the product of a hybrid origin. Based on morphology, the new species is assignable to the L. boulengeri group (sensu Abdala, 2007), and phylogenetic analyses of mitochondrial DNA indicate that L. parthenos is nested within L. darwinii, suggesting that the latter is the maternal ancestor of this species. Additional data are needed to identify the patrilineal ancestor.

A new Cyrtodactylus Gray, 1827 (Squamata, Gekkonidae) from the Shan Hills and the biogeography of Bent-toed Geckos from eastern Myanmar

A phylogenetic taxonomic analysis indicates that a newly discovered population of Cyrtodactylus from the vicinity of Ywangan Town in the Shan Hills, Shan State, Myanmar is a new species (C. ywanganensis sp. nov.) and the earliest diverging member of the linnwayensis group within the previously defined Indochinese clade. The DIVALIKE+J model of a BioGeoBEARS biogeographic analysis indicates that the Indochinese clade evolved in the Shan Hills and Salween Basin of eastern Myanmar and dispersed into Indochina on at least three separate occasions from 18.6-13.4 mya. Once there, uplift of the Tenasserim Mountains and Thai Highlands created the intermedius group, the oldhami group, and C. tigroides of western and southern Thailand which form sister lineages to the linnwayensis group, yathepyanensis group, and the sinyineensis group, respectively, of eastern Myanmar. Diverging lineages within the Indochinese clade highlight the importance of the Thai Highlands and Tenasserim Mountains in that groups evolution and speciation. The discovery of C. ywanganensis sp. nov. in karstic habitats in the Shan Hills continues to underscore the unrealized karst-associated herpetological diversity of this vast, relatively unexplored, upland region and the need for additional field studies.