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The US and Mexico share a common history in many areas, including language and culture. They face ecological changes due to the increased frequency and severity of droughts and rising energy demands; trends that entail economic costs for both nations and major implications for human wellbeing. We describe an ongoing effort by the Environment Working Group (EWG), created by The University of California's UC-Mexico initiative in 2015, to promote binational research, teaching, and outreach collaborations on the implications of climate change for Mexico and California. We synthesize current knowledge about the most pressing issues related to climate change in the US-Mexico border region and provide examples of cross-border discoveries and research initiatives, highlighting the need to move forward in six broad rubrics. This and similar binational cooperation efforts can lead to improved living standards, generate a collaborative mindset among participating universities, and create an international network to address urgent sustainability challenges affecting both countries.

Recently, Sinervo et al. (2010, Science, 328: 894-899) reported declines of lizard biodiversity due to local warming trends and altered thermal niches. Herein, we applied the Sinervo et al. (2010) physiological model to predict the local extinction risk of three species of lizard from Patagonia. Whereas the previous model used a single equation (for the extinctions of Blue Spiny Lizard (Sceloporus serrifer Cope, 1866) in the Yucatan Peninsula) relating environmental temperatures ([T.sub.e]) to hours of restriction (i.e., the period when lizards are forced into retreat sites because environmental temperatures are too high), we measured habitat-specific equations for the [T.sub.e] values of each species. We analyzed the vulnerability of Darwin's Ground Gecko (Homonota darwinii Boulenger, 1885), Bariloche Lizard (Liolaemus pictus (Dumeril and Bibron, 1837)), and Mountain Slope Lizard (Liolaemus elongatus Koslowsky, 1896) to climate change considering thermal physiological constraints on activity during the reproductive period. While Sinervo et al. (2010) predicted that the Phyllodactylidae family will not suffer from impacts of climate change, our physiological model predicted that 20% of the H. darwinii populations could become extinct by 2080. The physiological model also predicted that 15% of L. pictus populations and 26.5% of L. elongatus populations could become extinct by 2080. The most vulnerable populations are those located near the northern and eastern boundaries of their distributions. Key words: Liolaemus, Homonota, global warming, extinction risk, physiological model, climate change. Sinervo et al. (2010, Science, 328: 894-899) ont recemment fait etat de diminutions de la biodiversite des lezards en raison de tendances de rechauffement locales et de la modification de niches thermiques. Nous avons applique le modele physiologique de Sinervo et al. (2010) pour predire le risque de disparition locale de trois especes de lezards de Patagonie. Alors que le modele precedent utilisait une seule equation (pour les disparitions du lezard bleu epineux (Sceloporus serrifer Cope, 1866) dans la peninsule du Yucatan) reliant les temperatures ambiantes ([T.sub.e]) aux heures de restriction (c.-a-d. la periode durant laquelle les lezards sont forces de demeurer dans des sites de retrait parce que les temperatures ambiantes sont trop elevees), nous avons mesure des equations propres a l'habitat pour les valeurs de [T.sub.e] de chaque espece. Nous avons analyse la vulnerabilite du gecko de Darwin (Homonota darwinii Boulenger, 1885) et des lezards Liolaemus pictus (Dumeril and Bibron, 1837) et Liolaemus elongatus Koslowsky, 1896 aux changements climatiques en considerant les contraintes physiologiques thermiques sur l'activite durant la periode de reproduction. Alors que Sinervo et al. (2010) predisaient que le climat n'aura pas d'impacts sur la famille des phyllodactylides, notre modele physiologique predit que 20% des populations de H. darwinii pourraient disparaitre d'ici 2080. Le modele physiologique predit egalement que 15% des populations de L. pictus et 26,5% des populations de L. elongatus pourraient disparaitre d'ici 2080. Les populations les plus vulnerables sont celles qui sont situees pres des limites nord et est de leur aire de repartition. [Traduit par la Redaction] Mots-cles: Liolaemus, Homonota, rechauffement planetaire, risque de disparition, modele physiologique, changement climatique., Introduction Climate change to date has affected animal and plant populations in their phenology (Walther et al. 2002; Menzel et al. 2006; Parmesan 2006; Cleland et al. 2007), morphology (Harley [...]

Five alternative mating strategies among side-blotched lizards (Uta stansburiana) are examined, including the heritability of each strategy, morph fitness, and strategy links between the sexes.

An evolutionarily stable strategy model predicts oscillations in a three-morph mating system in the side-blotched lizards. Three phenotypes with distinct breeding patterns supplant each other cyclically in a variation of the scissors-paper-stone game. Population observations compared well with statistical probability models.

Several multi-trait experiments are conducted to present a comparative study of the importance of pleiotropy and signaller-receiver genes epistasis in the life-history of trade-offs. The signaller-receiver epistases are shown to create trade-offs among the multiple correlated traits affecting fitness.

The significance of correlational selection for optimal character combinations in natural environment is presented. Using an empirical example a general point about correlational selection that arises from interactions between predator behaviors, prey behavior, and prey morphology is illustrated.

The role of growth factor Bmp4 during the evolution in the beak morphology of Darwin's finches on Galapagos Islands is discussed. The shifts in the heterochronic-timing of ontogenetic events and heterotopic-spatial expression of ontogenetic events result in evolutionary changes to the developmental program of large-versus small-beaked species of Darwin's finch.

Intersexual ontogenetic conflict arises when an allele's fitness optimum differs between the sexes. Conflict is increasingly recognized as an important means of maintaining genetic variation at loci under chronic selection, however, genetic evidence of conflict has not yet been described in nature. We present the first evidence of ontogenetic conflict from a wild population of the side-blotched lizard, Uta stansburiana, showing that genes for male body-size confer high or low fitness depending on sex of the progeny. We have also measured strong genetic correlations between sire body mass, performance traits, throat colour alleles, progeny body mass, egg mass, and egg laying dates. Selection on body size and male performance alleles of males was antagonized by selection on the same alleles that control life history traits of females, indicating genetic conflict between the sexes. This ontogenetic conflict resolves the paradoxical finding that additive genetic variation is maintained in traits under chronic natural and sexual selection. Furthermore, male and female performance traits experience countervailing forces of natural and sexual selection. We review other systems in which ontogenetic conflict might act on male and female performance traits. Mechanisms of hormonal regulation are conserved among vertebrates.

Elevated levels of circulating corticosterone commonly occur in response to stress in wild vertebrates. A rise in corticosterone, usually in animals of subordinate rank, results in a variety of effects on behavior and physiology. Behavioral and physiological responses to short term increases in corticosterone are well studied. In contrast, the effects of chronic elevated levels of corticosterone are poorly understood, particularly in lizards. Here, we examined the long term effects of exogenous corticosterone on locomotor performance, resting and active metabolic rate, and hematocrit in male side-blotched lizards Uta stansburiana. Corticosterone implantation resulted in higher levels of stamina relative to sham-surgery controls in both the field and laboratory. In addition, lizards with elevated corticosterone exhibited lower resting metabolic rates relative to controls. Corticosterone had no effect on peak activity metabolism, but did result in faster recovery times following exhaustive exercise. We suggest that elevated levels of corticosterone in response to dominance interactions promote enhanced locomotor abilities, perhaps as a flight response to avoid agonistic interactions. Furthermore, stressed lizards are characterized by lower resting metabolic rates, which may serve as strategy to conserve energy stores.

Maternal effects can have profound influences on offspring phenotype and survivorship. Female side blotched lizards (Uta stansburiana) have the ability to regulate clutch and egg size, as well as levels of hormones (e.g. corticosterone and progesterone) in their eggs. In adult Uta, corticosterone and progesterone influence social interactions and degree of aggressiveness. Lizards with higher levels of corticosterone and progesterone are usually more aggressive and aware, making them potentially more likely to avoid predation. Thus, maternal manipulation of hormones and hatchling size may have an effect on hatchling predator avoidance behaviors. In this study, we experimentally elevated levels of progesterone and corticosterone in female Uta and their eggs prior to incubation. We also manipulated the size of some hatchlings via yolk removal or follicle ablation. We then video-taped and evaluated the predator avoidance behaviors exhibited by the hatchlings in response to a simulated snake. We measured the approach distance of the snake and the initial speed and direction in which the hatchling ran. We also measured their maximum sprint speed on a 1.5 meter track. Overall, behavior was highly variable. Approximately 1/3 of the hatchlings did not run until they were touched by the snake, which could indicate use of crypsis for predator avoidance by hatchlings.

Physiological performance can influence foraging ability, predator avoidance, or reproductive success, and is therefore often measured in adult animals, with implications for fitness discussed. However, animals are subject to predation pressure and foraging needs throughout their lives. We tracked physiological performance of ~90 lab-reared side-blotched lizards (Uta stansburiana) from just after hatching to reproductive maturity, one year later. Trials were conducted in June 2002, September 2002, December 2002, and May 2003. Maximum sprint speed, willingness to run (number of stops made), and number of reversals (an anti-predator tactic) were measured on a 150-cm racetrack (using either digital video or photocells and datalogger with timer). Stamina (time run on a treadmill until loss of righting response) was measured for the last three trials. Performance was highly variable and improved with age in the first three trials (higher sprint speed, fewer stops and reversals), but declined in the fourth trial, possibly due to poor recovery of the animals from hibernation; data for this trial were excluded from most analyses. There was a slight but significant effect of body mass on sprint speed within Trial 1 and on stamina within Trial 2, but no other within-trial effects of mass. Sprint speed, stamina, and number of stops had low but significant repeatabilities.

Male side-blotched lizards (Uta stansburiana) in Los Banos, CA exhibit three alternative mating strategies (ultra-dominant, mate guarding, and sneaking) that are genetically controlled and associated with throat color (orange, blue, and yellow, respectively). This variation in reproductive behavior can be expected to influence the lizards energy needs and physiological performance in the field. During the breeding season, we measured maximum sprint speed and stamina of ~200 just-captured male Uta in the laboratory, and then injected them with doubly-labeled water and released them at their home territories to measure field metabolic rate (FMR) and water turnover. 89 lizards survived to be recaptured ~28 days later, and 48 of those survived to a second recapture another ~19 days later. Lizards with higher stamina were more likely to survive; survivorship was not influenced by throat color or FMR. Mass-adjusted FMR and water turnover were higher during the first measurement period, and there was a slight but significant effect of throat color, with orange males having the lowest FMR and blue-yellow heterozygous males having the highest. FMR is therefore influenced by genotype (mating strategy) and may also be affected by the social environment in which the lizard is found.

Predator avoidance is one of the important determinants of survival, and ultimately of fitness. Antipredator behaviors and color patterns of reptiles may be correlated with each other and with physiological performance. We investigated the relationships among these traits in hatchling side-blotched lizards (Uta stansburiana). Using a digital video camera, we measured maximum sprint speed and numbers of stops and reversals made by lizards ranging from zero to five days old during three passes along a 0.5 m track. Back patterns were scored on a numerical scale ranging from striped to barred. There was a slight but significant effect of snout-vent length on sprint speed; there was no effect of age or back pattern score on size-corrected sprint speed, number of stops, or number of reversals. There was a significant effect of clutch on all measures. Lizards with lower maximum sprint speeds also stopped more frequently and made more reversals, suggesting that poorer performers are less willing to run and may use different predator avoidance tactics. The relationship between hatchling performance and parental performance was examined to evaluate the heritability of sprint speed.

In the conditional strategy model, divergence in reproductive phenotypes depends on whether the individual's condition is above or below a genetically determined threshold. The relative contribution of the genetic and environmental components that lead to the expression of a reproductive tactic by an individual is not well understood. In the present field study, we determined when condition diverged between males that develop the mature parr phenotype and those that do not in Atlantic salmon (Salmo salar). We also investigated the uniformity of the threshold value in the population. We sampled mature parr and immature males at age one, of the same population at six different sites for four consecutive years. Our study provides an example of the interaction of genotype and environment on the expression of a reproductive tactic. Size was significantly greater for future mature parr than for future immature males as early as 20 days after hatching (emergence), suggesting that there may be a parental effect component in the tactic adopted, since no exogenous feeding takes place before this time. Size advantage at emergence was maintained through the next spring at age one to different degrees depending on the year, thus suggesting the presence of an environmental component of tactic expression. Our results support the contention that within the conditional strategy, the environment faced by a male and his condition at the moment of reproduction consistently predicts neither the environment faced by his offspring nor the fitness they will obtain by expressing the same tactic as their father. Furthermore, higher mean size at a site did not always translate into a higher proportion of mature parr, therefore supporting the hypothesis that thresholds vary across habitats within the same population. [ABSTRACT FROM AUTHOR]