Research | enrique

Current Projects

Sex determining mechanism in the eastern Collared Lizard (C. collaris): Crotaphytus collaris has been suggested to be GSD, but karyotype studies do not report sex chromosomes. One of our studies indicates that extremes of low and high constant incubation temperatures produce more male than female hatchling lizards. In our most recent study, using qPCR, we demonstrated that free-ranging C. collaris possesses sex-based gene dosage, this result is consistent with the presence of sex microchromosomes. Our results, combined, suggest a temperature override that switches genotypic females to phenotypic males at high and low constant incubation temperatures. Thus, it is likely that C. collaris possess sex microchromosomes in an XX/XY pattern and that extreme incubation temperatures alter the sex-determining pathway; XX individuals develop as phenotypic males.

Group living, parental care, age structure, and genetic relatedness in Liolaemus leopardinus, a high-elevation lizard from the Andes of Chile: Liolaemus leopardinus, a viviparous lizard endemic to central Chile. Results from a pilot study suggested that these lizards form social groups, but the neonates are found among those groups. In 2013, I discovered that the mother leaves the social group to give birth underneath flat rocks and stays with her neonates some 24 h. I employed field and laboratory studies to determine whether offspring benefit from neonate care via thermoregulation, predator avoidance, or provisioned nutrition. I know there is a chemical recognition between mothers and their offspring and that neonates consume adult feces, which is the way the microflora necessary for them to digest plant matter is transferred from parent to offspring. In addition, I performed genetic analyses of the relatedness of group members and to determine if juveniles inhabit groups with their parents. To determine the age of the individuals within a group, I made use of skeletochronology analyses. I plan to expand the results regarding kin chemical recognition.

Liolaemus lizard species as storytellers on the effects of climate change in temperate South America: My team and I are comparing the elevational distributions of lizard species collected in 1986 with their distributions now, hypothesizing that the increase of environmental temperatures has caused species to move up-slope and evolve in a short period of time. We extended our survey ca. 200 meters upwards from the upper elevation limit of the original study site (replicating area of the original site) and recorded relative species density at this upper site separately. The study is the first to test the idea of climate-linked upward range shifts in lizards of the temperate Andes in Chile. We pinpointed what species are shifting their elevations upward because of the recent rapid increase in ambient temperatures and related those shifts to natural features that could amplify extinction risks, and anthropogenic activities that could increase extinction risks. Also, we will determine if the species have evolved morphologically in response to climate change, controlling for changes in land use. We will conduct multivariate morphometric comparisons of lizards from 30 years ago with those recently collected from the exact same sites. For the second step of our research program, we conducted intensive population surveys of those species that have moved upward into the new habitat to appraise their conservation status and implement conservation action as necessary. Our results suggest that all our hypotheses were correct. The relative density of some lizard populations is so low that they can be considered locally extinct. A few species already increased their altitudinal distribution and a few species have rapidly evolved in the last 30 years as a response to the effects of climate change.

Ontogenetic dorsal pattern or phenotypic plasticity in Liolaemus belli: Many vertebrate species belonging to different taxa show ontogenetic, directional changes in coloring or pattern. Ontogenetic changes on those traits are very common in reptiles yet remain a poorly understood phenomenon. Liolaemus bellii is a viviparous lizard species inhabiting rocky mountainous areas of central Chile. It is common to see adults basking on top of rocks. Subjects of the species show a very distinctive chevron dorsal pattern, but it is absent in some juveniles and/or adults. In 2017, we collected subjects from a population located at ~3000 m in central Chile. For each subject we recorded the presence or absence of dorsal pattern, microhabitat occupied and the height of perch, body and microhabitat temperature, age, and sex. We are testing if the presence or absence of the dorsal pattern is an ontogenetic trait that tends to fade with age and size or if it is associated to, microhabitat use, thermoregulation, or social hierarchy. We will determine the age of each subject via skeletochronology.

Predator escape ecology in Chilean lizards: My team and I measured the escape and flight distance in seven species of lizards of central Chile along an altitudinal gradient. The seven Liolaemus species vary with respect to body size and longevity, among many other respects. We postulated that longer-lived lizards are less likely to take predation risks than shorter-lived lizards since longer-lived ones have many more opportunities for reproduction. Short-lived lizards accept greater predation risks because they cannot afford to give up time for other activities. We are using toe tips from the largest individuals of each species in museum collections to determine maximum age via skeletochronology, which we will relate to escape variables.

Past projects

Comparison of escape behavior between solitary versus grouped Liolaemus leopardinus from the central Chilean Andes: The social structure and behavior of L. leopardinus make it a great model to study responses to predation in solitary and grouped individuals. Based on both Optima Escape Theory and the dilution effect theory, we hypothesized that predation risk expressed as flying initiation distance should be smaller in grouped L. leopardinus and greater in solitary individuals of the species--a benefit of group living.

Ecology of the herpetofauna in the Chinipas Canyon, Chihuahua: Chínipas Canyon is located in the southwestern portion of the state of Chihuahua. Until 2007, in any of 22 herpetological collections of the United States and Canada curatorial records were kept, only the amphibians and reptiles collection kept in the Laboratory of Ecology-UBIPRO possessed specimens from Chínipas and Guazapares, municipalities that make up the Canyon. Apparently, Chínipas herpetofauna was not studied until the early '90s. It is considered that the herpetofaunal list of the Canyon is partially known, and the herpetofaunistic structure has not been examined in greater detail. This thesis can be divided into two studies, the first one involved to list the amphibians and reptiles registered at Chínipas Canyon, to examine amphibians and reptile monthly diversity, to determine the herpetological α diversity and to find out the herpetofaunistic similarity between plant associations. The results indicated that the species accumulation curve reached the asymptote in the seventh sampling with 59 species. The Chao1 index revealed the potential presence of 62 species, the completeness of the list is 96 %. The Shannon index showed that May and August are the most diverse months and the uniformity was higher in May, October, and November. In subtropical deciduous forest was recorded the highest species number (43) and oak forest the least one (20). In the pine forest, we found a higher number of species in an oak forest. The Bray-Curtis index indicated that the oak forest and pine forest had the greatest species affinity. The second part of this thesis involved to assess the share of space and time between cohabiting lizard species. The niche breadth value was determined using Simpson’s formula and niche overlap using Pianka’s index. Simpson’s formula results, in microhabitat use, suggest that individuals tend to be specialists and generalists during the activity hours. It is determined that the resource that structures lizard communities located in the Canyon are the space.

Análisis taxonómico de las subespecies de Boa constrictor descritas para territorio mexicano: Boa constrictor es una de las especies de serpientes que presentan amplia distribución enLatinoamérica, localizándose desde México hasta Argentina. En territorio mexicano esta serpiente se distribuye desde la parte norte del país hacia el sur y el este por ambas costas hasta la porción sureste, en algunos estados del centro, y en las Islas Marías y Cozumel. A la fecha se han descrito tres subespecies B. c. imperator, B. c. mexicana y B. c. sigma. Sin embargo, varios autores han sinonimizado las dos últimas subespecies con B. c. imperator, generalmente basados en un número reducido de caracteres morfológicos y criterios taxonómicos no uniformes, además de la distribución geográfica de la serpiente. Durante los últimos años no se ha realizado corroboración alguna sobre su situación taxonómica, ni distribución geográfica.