Robert E. Espinoza

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Herbivory has evolved in many groups of vertebrates, but it is rare among both extinct and extant nonavian reptiles. Among squamate reptiles, (lizards, snakes, and their relatives), <2% of the >7,800 species are considered to be herbivorous, and herbivory is restricted to lizards. Here, we show that within a group of South American lizards (Liolaemidae,(More)
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(More)
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 (T(sel)), (3) the body temperature at which the righting(More)
Many of the threats to the persistence of populations of sensitive species have physiological or pathological mechanisms, and those mechanisms are best understood through the inherently integrative discipline of physiological ecology. The desert tortoise was listed under the Endangered Species Act largely due to a newly recognized upper respiratory disease(More)
The Liolaemus elongatus group currently includes eight species (including the species described herein) of mid-sized, long-tailed, primarily saxicolous lizards. Members of this lineage are distributed in northwestern Argentina along the Andean Cordillera south to the Patagonian Steppe (27–44Њ S) and over a wide range of elevations (350–3900 m). Here we(More)
Aggregating has been widely studied in a variety of animals and found to have important benefits in terms of sociality, courtship, predator avoidance and physiology. Several species of nocturnal geckos form diurnal aggregations; however, little is known about the benefits of these groupings. We conducted a series of experiments to determine the benefit of(More)
Animals that are unable to meet their metabolic needs should adopt compensatory behaviors to mitigate their energetic deficits. Voluntary hypothermia is one such energy-saving strategy. Physiological constraints associated with the digestion of plant tissues, however, may limit the thermoregulatory options of herbivorous ec-totherms. In this laboratory(More)
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(More)
The Colorado Trust is a grantmaking foundation dedicated to achieving access to health for all Coloradans. To learn more about the foundation, its grants and evaluations, please visit Thanks go to the following individuals who provided feedback on drafts of the case studies and cross-cultural competence considerations for the(More)