Publications

acclimation of the critical thermal maximum of the reptile urosaurus ornatus.		1955	17748800
reproductive cycles of the iguanid lizards urosaurus ornatus and uta stansburiana in southeastern arizona.		1964	14191392
water loss, desiccation tolerance, and survival under desiccating conditions in 11 species of caribbean anolis : evolutionary and ecological implications.	1. rates of water loss and tolerance to desiccation were examined in 11 species of caribbean anolis and the sonoran desert iguanid lizard, urosaurus ornatus. 2. rates of water loss ranged from 0.07% body wt/h (a. bonairensis) to 0.43% body wt/h (a. distichus). 3. there were significant correlations between habitat rainfall and both the rates of water loss (p<0.005) and the maximum time of survival (ltmax) (p<0.01) for the 11 species of anolis. species from areas of low rainfall generally had low ...	1977	28308644
tree lizard (urosaurus ornatus) territories: experimental perturbation of the sex ratio.		1987	29357184
defense of mates: a territory departure rule for male tree lizards following sex-ratio manipulation.	male tree lizards (urosaurus ornatus) abandon their territories following the removal of potential mates. departure time averages 25 days but varies from 1 to 7 weeks. we show that most of the variation (r2=0.78) in departure of males can be accounted for by the number of females removed from male territories and adjacent trees. males occupying higher quality territories (more potential mates) have short departure times, whereas males on poorer territories (fewer fameles) stay longer after femal ...	1987	28311401
reciprocal changes in corticosterone and testosterone levels following acute and chronic handling stress in the tree lizard, urosaurus ornatus.	to examine the reciprocal interactions among gonadal and adrenal steroid secretion, male tree lizards (urosaurus ornatus) were subjected to two forms of stress. they were subjected either to the acute stress of being held in collecting bags for up to 4 hr or to the chronic stress of being maintained in individual cages in the laboratory for up to 3 weeks. in both cases, levels in stressed animals were compared to levels in free-living animals as controls. under both conditions plasma levels of c ...	1991	2019396
behavioral and hormonal correlates of alternative reproductive strategies in a polygynous lizard: tests of the relative plasticity and challenge hypotheses.	species with alternative reproductive tacts are good models to investigate the poorly understood question of whether individual variation within sexes results from the same physiological mechanisms that control variation between sexes. we have shown previously that adult male tree lizards, urosaurus ornatus, of different throat color morphs express different levels of aggression in the laboratory. further field results support the suggestion that the two morphs practice alternative reproductive ...	1992	1478640
manipulation of egg production reveals costs of reproduction in the tree lizard (urosaurus ornatus).	life-history theory predicts that the allocation of energy to current reproduction is associated with a decrement in future fecundity, future survival, or both. i treated this notion as the "cost hypothesis", and tested the assumption that current reproduction exacts a "cost" in future survival and fecundity. surgical manipulations of egg production were applied to natural populations of the tree lizard, urosaurus ornatus, in south western new mexico by yolkectomy surgery in two different years. ...	1994	28307007
early exposure to androgens affects adult expression of alternative male types in tree lizards.	males of many species exhibit strongly dimorphic reproductive behavior and morphology associated with alternative reproductive tactics. little is known about the physiological control of these individual differences. the relative plasticity hypothesis proposes that such within-sex differences arise from either organizational or activational actions of sex steroid hormones depending on whether adults can switch tactics or not. this hypothesis predicts that differences between individuals in a spe ...	1994	8034285
discovery of an alpha-melanotropin antagonist effective in vivo.	a hybrid analogue, h-his-d-arg-ala-trp-d-phe-lys-nh2, was designed based upon the primary structures of a growth hormone-releasing peptide analogue, [his1,lys6]ghrp, and the msh fragment, ac-alpha-msh(6-11)-nh2. in vitro studies demonstrated the alpha-msh antagonistic efficacy of the analogue in the lizards sceloporus jarrovii and urosaurus ornatus. in live white background-adapted s. jarrovii previously injected with the antagonist (10 nmol/5 g b.wt.), maximal skin darkening induced by alpha-ms ...	1994	7937337
hormonal responses to aggression vary in different types of agonistic encounters in male tree lizards, urosaurus ornatus.	hormonal responses to male-male interactions have been detected in some studies of vertebrates but not others. one hypothesis that may partially explain these discrepancies is that differences in the duration of male-male interactions cause different hormonal responses. in social systems based on dominance-subordinance hierarchies interactions often last longer than if exclusive territories are maintained. tests of the hypothesis that encounter duration explains discrepancies in hormonal respons ...	1995	7782065
influence of androgens on differentiation of secondary sex characters in tree lizards, urosaurus ornatus.	vertebrates species vary in the degree to which the sexes differ in their expression of secondary sex characters, which can be expressed in one sex but not the other, fully expressed in both sexes, or expressed to different degrees in the two sexes. sex steroid hormones contribute to the development of sex differences, either through action early in life (organization), following sexual maturation (activation), or both. however, relatively little is known about the contributions of sex steroid h ...	1995	7713387
a critical period for the organization of alternative male phenotypes of tree lizards by exogenous testosterone?	male tree lizards (urosaurus ornatus) exhibit permanent adult differences in color and size that are functionally linked with behavioral differences: males with a central blue throat patch are territorial, more aggressive, and smaller than males lacking the patch, who are nomads or satellites foregoing territory defense. gonadectomy or long-lasting hormone implants in hatchlings affect the development of these permanent adult differences, but similar manipulations in adults are ineffective. anal ...	1996	8840901
male morphs in tree lizards have different testosterone responses to elevated levels of corticosterone.	changes in circulating glucocorticoid and androgen levels mediate agonistic behaviors in many vertebrates. individual variation in the magnitude of the glucocorticoid response to stressful stimuli, the negative effects of elevated glucocorticoid levels on androgen levels, or both could mediate individual differences in subsequent agonistic behavior. in a series of previous studies, we found that both alternative male reproductive morphs in the tree lizard, urosaurus ornatus, can exhibit elevated ...	1997	9245535
sympathetic mediation of stress and aggressive competition: plasma catecholamines in free-living male tree lizards.	the sympathetic nervous system and adrenal catecholaminergic tissue act to prepare an animal for "fight or flight" by release of catecholamines into synapses and plasma. however, few studies have measured plasma catecholamines in nonmammalian vertebrates and none have measured them in free-living animals. we report plasma levels of norepinephrine (ne), epinephrine (epi) and dopamine (da) in free-living tree lizards (urosaurus ornatus) bled in the field: 1) immediately after capture, 2) after 10 ...	1997	9145930
comparative biological activities of alpha-msh antagonists in vertebrate pigment cells.	we have previously reported that melatonin was an effective lightening agonist in the teleost synbranchus marmoratus, the amphibians rana pipiens and bufo ictericus, and in the lizard anolis carolinensis. the hormone, previously applied to the preparations, effectively inhibited alpha-msh darkening activity in a dose-independent manner, and was also able to reverse msh-induced darkening. we presently describe the inhibitory effect of the indoleamine on the murine melanoma cell proliferation. int ...	1997	9073503
size distributions and sex ratios of colonizing lizards.	this paper reports the body size distributions and sex ratios of four species of phyrnosomatid lizard that colonized experimentally created density sinks. the experiments were conducted in western colorado in 1992, and lizards colonizing the habitats in 1993 were compared to those removed in 1992 and those present in 1991. lizards colonizing the density sinks were able to disperse from adjacent habitat. for two of the species (urosaurus ornatus and sceloporus undulatus), colonizing lizards were ...	1998	28307519
pharmacological adrenalectomy with mitotane.	the potential of mitotane (ortho, para'-ddd, commonly used to treat adrenal carcinomas in humans and dogs) was investigated as an alternative to surgical adrenalectomy in birds, salamanders, and lizards. house sparrows (passer domesticus) were injected twice daily with vehicle or one of two doses of mitotane (225 or 450 mg/kg), and basal and stress-induced levels of corticosterone (cort) were measured 3 and 5 days after injections. mitotane reduced basal cort levels to nondetectable and abolishe ...	2000	11042008
plasma steroid-binding globulin mediation of differences in stress reactivity in alternative male phenotypes in tree lizards, urosaurus ornatus.	plasma steroid-binding globulins, for example, corticosteroid-binding globulin and sex hormone-binding globulin (shbg), have been identified in a number of vertebrates. one possible function of these proteins is to regulate the amount of steroid delivery to target tissues, as only free steroids are believed to diffuse from the circulation to target cells. male tree lizards, urosaurus ornatus, exhibit alternative male reproductive tactics correlated with dewlap (throat-fan) coloration. males with ...	2000	11121294
morphology of the spermatozoa of the iguanian lizards uta stansburiana and urosaurus ornatus (squamata, phrynosomatidae).	the spermatozoa of uta stansburiana and urosaurus ornatus show the following squamate autapomorphies: a single perforatorium extending anteriorly from the apical tip of the paracrystalline subacrosomal cone; the presence of an epinuclear electron lucent region; intermitochondrial dense bodies; and the fibrous sheath extending into the midpiece. the acrosome vesicle is flattened and concentrically zoned apically; basally it overlies a subacrosomal cone which invests the nuclear rostrum. a stopper ...	2000	11085215
fighting from the right side of the brain: left visual field preference during aggression in free-ranging male tree lizards (urosaurus ornatus).	in a field study on male tree lizards (urosaurus ornatus), we tested the hypothesis that aggression is lateralized, and predicted that resident males should preferentially use the left-visual field (lvf)/right hemisphere in aggressive interactions with other males. this prediction was based on results for a small but taxonomically diverse number of vertebrates indicating a left-eye preference/ right hemisphere specialization for aggression. many lizards use postural displays to signal aggression ...	2001	12016354
sex differences in lipid metabolism during reproduction in free-living tree lizards (urosaurus ornatus).	understanding the relationship between energy metabolism and signals that regulate reproduction may provide insight into the coordination of the energetically costly behavioral and physiological events that occur during reproduction. significant changes in the utilization of stored lipids may occur during reproduction and the patterns of utilization observed often differ between females and males. changes in levels of stored lipid reserves have been described extensively in animals from many tax ...	2002	12392692
plasma corticosterone response to an acute stressor varies according to reproductive condition in female tree lizards (urosaurus ornatus).	the magnitude of the glucocorticoid response to a stressor can depend on both environmental and physiological context. one factor that has not been examined is whether females of different reproductive states have different responses to a stressor. we examined whether corticosterone (cort) increased after a 10 min handling stress in oviparous female tree lizards (urosaurus ornatus) that were vitellogenic (yolking follicles) or gravid (post-ovulatory). we found that stressed vitellogenic females ...	2002	12392687
environmental and endocrine correlates of tactic switching by nonterritorial male tree lizards (urosaurus ornatus).	animals often exhibit individual variation in their behavioral responses to the same stimuli in the biotic or abiotic environment. to elucidate the endocrine mechanisms mediating such behavioral variation, we have been studying a species of lizard with two distinct male phenotypes. here we document behavioral variation across years in one of the two male phenotypes of the tree lizard, urosaurus ornatus, and present hormone data that support an endocrine mechanism underlying this behavioral varia ...	2003	12614637
activation of aggressive behavior by progesterone and testosterone in male tree lizards, urosaurus ornatus.	testosterone is usually thought to be the major sex steroid regulating adult male territorial aggression in vertebrates. however, recent evidence has suggested a role for progesterone, as well as testosterone, in the organization of the two male reproductive phenotypes of tree lizards (urosaurus ornatus), which differ in adult levels of territorial behavior. in the present experiment we tested whether progesterone and testosterone could also play an activational role in the expression of adult a ...	2004	15028533
role of the adrenal gland in early post-hatching differentiation of alternative male phenotypes in the tree lezard (urosaurus ornatus).	during development, sex steroids are important in establishing differences between males and females. however, sex steroids also are involved in the development and maintenance of individual differences in morphology and behavior within each sex. as adults, male tree lizards (urosaurus ornatus) exhibit alternative reproductive tactics correlated with dewlap (throat fan) coloration. males with orange-blue dewlaps are aggressive and territorial, whereas males with orange dewlaps are less aggressiv ...	2004	14644647
the effects of stress on wound healing in male tree lizards (urosaurus ornatus).	exposure to stress can affect an organism's partitioning of resources among immune function and other organismal functions. however, measuring immune function is often difficult. recent studies show that the rate of cutaneous wound healing in laboratory rodents is a simple, integrated measure of stress-sensitive immune function. we investigated the use of this technique in tree lizards to test the hypotheses (1) that stress compromises wound healing and (2) that this effect is at least partially ...	2006	16188256
determinants of embryonic stage at oviposition in the lizard urosaurus ornatus.	relatively few squamate reptiles oviposit eggs with embryos at developmental stages greater than stage 30. to investigate potential proximate and ultimate bases of this phenomenon, we experimentally induced females of the lizard urosaurus ornatus to retain their eggs past the normal time of oviposition (nto). this procedure allowed us to determine whether the length of egg retention is fixed or facultative and to evaluate the effects of retention on embryos, hatchlings, and females. females were ...	2006	10603328
steroid hormone mediation of limbic brain plasticity and aggression in free-living tree lizards, urosaurus ornatus.	the neural mechanisms by which steroid hormones regulate aggression are unclear. although testosterone and its metabolites are involved in both the regulation of aggression and the maintenance of neural morphology, it is unknown whether these changes are functionally related. we addressed the hypothesis that parallel changes in steroid levels and brain volumes are involved in the regulation of adult aggression. we examined the relationships between seasonal hormone changes, aggressive behavior, ...	2006	16442108
phylogeography of the tree lizard, urosaurus ornatus: responses of populations to past climate change.	isolation due to both geological barriers and range contractions during the pleistocene glacial maxima has been an important cause of diversification of arid-adapted species in the north american deserts. tree lizards, urosaurus ornatus, are distributed across much of the southwestern arid regions and can tolerate a wide range of environments. thus, they may have avoided large-scale shifts in distribution caused by pleistocene climate change and any subsequent evolutionary impacts. cytochrome b ...	2007	17868290
trade-offs between the reproductive and immune systems: facultative responses to resources or obligate responses to reproduction?	a major challenge in biology is understanding how organisms partition limited resources among physiological processes. for example, offspring production and self-maintenance are important for fitness and survival, yet these critical processes often compete for resources. while physiological trade-offs between reproduction and immune function have been documented, their regulation remains unclear. most current evidence suggests that physiological changes during specific reproductive states direct ...	2007	17853993
corticosterone modulation of reproductive and immune systems trade-offs in female tree lizards: long-term corticosterone manipulations via injectable gelling material.	physiological trade-offs arise because multiple processes compete for the same limiting resources. while competition for resources has been demonstrated between reproduction and immune function, the regulation of this competition remains unclear. corticosterone (cort) is a likely mediator due to its dual role in mobilizing energy stores throughout the body and regulating physiological responses to stressors. we manipulated cort concentrations and resources in pre-reproductive and reproductive fe ...	2007	17690234
an analysis of the relative roles of plasticity and natural selection in the morphology and performance of a lizard (urosaurus ornatus).	evolutionary ecologists have devoted substantial attention to understanding which factors dictate processes of mortality within populations. our goal was to understand the dynamics of natural selection on two performance traits (bite force and sprint speed) and associated morphological variables. we first quantified performance and morphology for a sample of marked tree lizards (urosaurus ornatus) at the middle of the breeding season. we then sampled the same population in the nonbreeding season ...	2007	17453255
corticosterone stimulates hatching of late-term tree lizard embryos.	the regulation of hatching in oviparous animals is important for successful reproduction and survival, but is poorly understood. we unexpectedly found that ru-486, a progesterone and glucocorticoid antagonist, interferes with hatching of viable tree lizard (urosaurus ornatus) embryos in a dose-dependent manner and hypothesized that embryonic glucocorticoids regulate hatching. to test this hypothesis, we treated eggs with corticosterone (cort) or vehicle on day 30 (85%) of incubation, left other ...	2007	17208477
arginine vasotocin (avt) immunoreactivity relates to testosterone but not territorial aggression in the tree lizard, urosaurus ornatus.	the neuropeptide arginine vasotocin (avt) and its mammalian homologue arginine vasopressin (avp) are neuromodulators known to be steroid sensitive and associated with social behaviors in a number of vertebrate taxa. however, the role of avt/p in the regulation of aggression remains unclear and contrasting effects of this peptide on aggression are seen in differing species and contexts. in this study, we used immunohistochemistry to examine the effects of testosterone on the avt system in male an ...	2008	19018131
aggression frequency and intensity, independent of testosterone levels, relate to neural activation within the dorsolateral subdivision of the ventromedial hypothalamus in the tree lizard urosaurus ornatus.	the mechanisms by which testosterone regulates aggression are unclear and may involve changes that alter the activity levels of one or more brain nuclei. we estimate neural activity by counting immunopositive cells against phosphorylated cyclic amp response element binding protein (pcreb). we demonstrate increased pcreb immunoreactivity within the dorsolateral subdivision of the ventromedial hypothalamus (vmhdl) following an aggressive encounter in male tree lizards urosaurus ornatus. this immun ...	2008	18021776
steroid hormones alter neuroanatomy and aggression independently in the tree lizard.	steroid hormones effect changes in both neuroanatomy and aggressive behavior in animals of various taxa. however, whether changes in neuroanatomy directly underlie changes in aggression is unknown. we investigate this relationship among steroid hormones, neuroanatomy, and aggression in a free-living vertebrate with a relatively simple nervous system, the tree lizard (urosaurus ornatus). weiss and moore [1] manipulated testosterone and progesterone levels in adult male tree lizards and found that ...	2008	17996258
immune function varies with reproductive stage and context in female and male tree lizards, urosaurus ornatus.	competition among physiological processes for limited resources often results in trade-offs. key among these processes is reproduction and immune function, and optimizing both appears to be difficult. to test the hypothesis that the resource demands of reproduction compromise immune function, we measured rates of wound healing, an integrated measure of innate immunity, across different reproductive stages in female and male tree lizards (urosaurus ornatus) in both the field and the laboratory. t ...	2008	17517411
variation in stress and innate immunity in the tree lizard (urosaurus ornatus) across an urban-rural gradient.	the urban environment presents new and different challenges to wildlife, but also potential opportunities depending on the species. as urban encroachment onto native habitats continues, understanding the impact of this expansion on native species is vital to conservation. a key physiological indicator of environmental disturbance is the vertebrate stress response, involving increases in circulating glucocorticoids (i.e. corticosterone), which exert influence on numerous physiological parameters ...	2008	18594834
acute corticosterone elevation enhances antipredator behaviors in male tree lizard morphs.	in response to stressful events, most vertebrates rapidly elevate plasma glucocorticoid levels. corticosterone release stimulates physiological and behavioral responses that can promote survival while suppressing behaviors that are not crucial to immediate survival. corticosterone also has preparatory effects for subsequent stressors. using male tree lizards (urosaurus ornatus), we tested our prediction that elevated corticosterone is important for mediating and enhancing antipredator behaviors. ...	2009	19281811
isolation and characterization of microsatellite markers in tree lizards (urosaurus ornatus).	tree lizards (urosaurus ornatus) are a highly accessible species useful in testing theories of life-history evolution and behavioural ecology. a polymerase chain reaction-based method was used to isolate nine polymorphic tetranucleotide microsatellite loci from the genome of these lizards. the isolated loci displayed 5 to 9 alleles in the populations screened. observed heterozygosity ranged from 0.333 to 0.900. results indicate these loci now provide a basis to study mate choice, parentage, and ...	2009	21564702
leptin as a physiological mediator of energetic trade-offs in ecoimmunology: implications for disease.	organisms must distribute sufficient energy among different and often competing physiological systems. this task can become challenging, however, as resources are often limiting, resulting in energetic trade-offs. for example, energetically based trade-offs between the reproductive and immune systems are common across taxa, yet the regulatory mechanisms underlying these trade-offs remain unclear. the adipose tissue hormone leptin is an ideal candidate for the modulation of energetic trade-offs b ...	2011	21940777
evolution of viviparity in sceloporine lizards: in utero po2 as a developmental constraint during egg retention.	reptilian viviparity evolves through selection for increasingly prolonged egg retention within the oviduct. in the majority of sceloporine lizard species, however, egg retention past the normal time of oviposition results in retarded or arrested embryonic development. in this study, we tested the hypothesis that the amount of embryonic development normally attained in utero is directly related to in utero oxygen partial pressure (po(2)). the three species of sceloporine lizards we used are chara ...	2013	16691524
preference for male traits differ in two female morphs of the tree lizard, urosaurus ornatus.	non-random female mating preferences may contribute to the maintenance of phenotypic variation in color polymorphic species. however, the effect of female preference depends on the types of male traits used as signals by receptive females. if preference signals derive from discrete male traits (i.e., morph-specific), female preferences may rapidly fix to a morph. however, female preference signals may also include condition-dependent male traits. in this scenario, female preference may differ de ...	2014	25033282
ecological divergence among colour morphs mediated by changes in spatial network structure associated with disturbance.	differences in individual behaviour affect social interactions and contribute to the spatial structuring of animal populations. however, disturbance should also affect spatial networks by altering habitat heterogeneity and resource availability. variation in resource availability should perturb the frequency and nature of social and ecological interactions within a population by affecting the spatial distribution of individuals. in disturbed habitats where resources are limiting, spatial relatio ...	2014	24889087
trophic niche divergence among colour morphs that exhibit alternative mating tactics.	discrete colour morphs associated with alternative mating tactics are assumed to be ecologically equivalent. yet suites of behaviours linked with reproduction can also favour habitat segregation and exploitation of different prey among morphs. by contrast, trophic polymorphisms are usually attributed to morphs exhibiting habitat or prey selectivity. an alternative hypothesis is that habitat variation generates a trophic polymorphism driven by differences in morph reproductive behaviour, the spat ...	2016	27152203
stable carbon and nitrogen isotope discrimination and turnover in a small-bodied insectivorous lizard.	laboratory experiments are useful for estimating the carbon and nitrogen isotope discrimination factors and turnover rates that are critical for drawing field-based inferences on consumer diets using stable isotopes. although the utility of these discrimination factors is widely recognized, work in terrestrial systems has largely been limited to studies involving mammals and birds. in contrast, scant attention has been paid to the application of isotopic techniques to reptiles, despite their bro ...	2016	26999652
tree lizard (urosaurus ornatus) growth decreases with population density, but increases with habitat quality.	habitat selection models can explain spatial patterns in the relative abundance of animals in different habitats based on the assumption that fitness declines as density in a habitat increases. ectotherms, such as lizards, may not follow predictions of density-dependent habitat selection models because temperature, which is unaffected by density, strongly influences their habitat selection. if competition for limited resources decreases fitness, then crowding should cause a decrease in body size ...	2018	30096219
ornate tree lizards (urosaurus ornatus) thermoregulate less accurately in habitats of high thermal quality.	temperature plays a critical role for ectotherm performance and thus for fitness. ectotherms, since unable to regulate their body temperature internally, use behavioural thermoregulation to maintain their body temperature within a range that maximizes performance. according to the cost-benefit model of thermoregulation, investment into thermoregulation is dictated by the trade-off between the costs and benefits of thermoregulating. the thermal quality of the environment is a major cost of thermo ...	2019	31657742
antagonistic responses of exposure to sublethal temperatures: adaptive phenotypic plasticity coincides with a reduction in organismal performance.	a fitness benefit of phenotypic plasticity is the ability of an organism to survive short-term, deleterious environmental fluctuations. yet the influence of selection on plasticity in modulating shifts in phenotypic traits remains unclear. short-term phenotypic plasticity in thermal tolerance traits is attained by exposure to sublethal hot or cold temperatures (i.e., the hardening response). heat hardening is expected to buffer organisms from the unpredictability of extreme thermal fluctuations ...	2019	31553209