DSpace Angular :: Browsing by Author "Vasquez, Rodrigo A."

Browsing by Author "Vasquez, Rodrigo A."

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A Sarcocystid Misidentified as Hepatozoon didelphydis: Molecular Data from a Parasitic Infection in the Blood of the Southern Mouse Opossum (Thylamys elegans) from Chile
(2008) Merino, Santiago; Vasquez, Rodrigo A.; Martinez, Javier; Celis-Diez, Juan L.; Martinez-De La Puente, Josue; Marin-Vial, Paula; Sanchez-Monsalvez, Inocencia; Peirce, Michael A.
The blood of 21 adult South American mouse opossums (Thylamys elegans) captured from April through August of 2005 in central Chile was examined for parasites. Light microscopic analysis of blood smears initially suggested that a highly pleomorphic Hepatozoon species typical of American opossums was infecting erythrocytes. Unexpectedly, amplification by PCR and sequencing of a DNA fragment of the small subunit rDNA combined with phylogenetic analyses indicated that the parasite is not a member of the suborder Adeleorina, which includes the Haemogregarina and Hepatozoon species, but that it is a clearly distinct member of the suborder Eimeriorina, which includes the cyst-forming family Sarcocystidae. Therefore, a reclassification of this unusual intraerythrocytic apicomplexan will require additional life cycle, microscopic, and molecular analyses.
Associations among MHC genes, latitude, and avian malaria infections in the rufous-collared sparrow (Zonotrichia capensis)
(2024) de Aguilar, Juan Rivero; Barroso, Omar; Bonaccorso, Elisa; Cadena, Hector; Hussing, Lucas; Jorquera, Josefina; Martinez, Javier; Martinez-de la Puente, Josue; Marzal, Alfonso; Miranda, Fabiola Leon; Merino, Santiago; Matta, Nubia E.; Ramenofsky, Marilyn; Rozzi, Ricardo; Valeris-Chacin, Carlos E.; Vasquez, Rodrigo A.; Vianna, Juliana A.; Wingfield, John C.
The major histocompatibility complex (MHC) is a genetic region in jawed vertebrates that contains key genes involved in the immune response. Associations between the MHC and avian malaria infections in wild birds have been observed and mainly explored in the Northern Hemisphere, while a general lack of information remains in the Southern Hemisphere. Here, we investigated the associations between the MHC genes and infections with Plasmodium and Haemoproteus blood parasites along a latitudinal gradient in South America. We sampled 93 rufous-collared sparrows (Zonotrichia capensis) individuals from four countries, Colombia, Ecuador, Peru, and Chile, and estimated MHC-I and MHC-II allele diversity. We detected between 1-4 (MHC-I) and 1-6 (MHC-II) amino acidic alleles per individual, with signs of positive selection. We obtained generalized additive mixed models to explore the associations between MHC-I and MHC-II diversity and latitude. We also explored the relationship between infection status and latitude/biome. We found a non-linear association between the MHC-II amino acidic allele diversity and latitude. Individuals from north Chile presented a lower MHC genetic diversity than those from other locations. We also found an association between deserts and xeric shrublands and a lower prevalence of Haemoproteus parasites. Our results support a lower MHC genetic in arid or semi-arid habitats in the region with the lower prevalence of Haemoproteus parasites.
Basal metabolism is correlated with habitat productivity among populations of degus (Octodon degus)
(2009) Bozinovic, Francisco; Rojas, Jose M.; Broitman, Bernardo R.; Vasquez, Rodrigo A.
Several competing hypotheses attempt to explain how environmental conditions affect mass-independent basal metabolic rate (BMR) in mammals. One of the most inclusive is the hypothesis that associates BMR with food habits, including habitat productivity. The effects of food habits have been widely investigated at the interspecific level, and variation between individuals and populations has been largely ignored. Intraspecific analysis of physiological traits has the potential to compensate for many pitfalls associated with interspecific analyses and serve as a useful approach for evaluating hypotheses regarding metabolic adaptation. Here we tested the effects of climatic variables (mean annual rainfall=PP, mean annual temperature=TA), net primary productivity (NPP) and the de Martonne index (DMi) of aridity on mass-independent BMR among four populations of the caviomorph rodent Octodon degus along a geographic gradient in Chile. BMR was measured on animals maintained in a common garden acclimation set-up, thus kept under the same environment and diet quality for at least 6 months. Mass-independent BMR was significantly different among degu populations showing a large intraspecific spread in metabolic rates. A very large fraction of interpopulational variability in mass-independent BMR was explained by NPR PP and DMi. Our results were conclusive about the effects of habitat productivity on setting the level of mass-independent BMR at the intraspecific-interpopulational level. (C) 2009 Elsevier Inc. All rights reserved.
BREEDING BIOLOGY OF THE SOUTHERN HOUSE WREN ON CHILOE ISLAND, SOUTHERN CHILE
(2012) Ippi, Silvina; Vasquez, Rodrigo A.; Moreno, Juan; Merino, Santiago; Villavicencio, Camila P.
We studied the breeding biology of a Southern House Wren (Troglodytes aedon chilensis) population using nest boxes on Chiloe Island, southern Chile (41 degrees S) to make latitudinal comparisons at the intraspecific level. There were no significant differences in body size between adult males and females, although wings were significantly longer in males. Clutch size averaged 4.3 eggs per nest, and brood size was 3.9 nestlings. Egg size averaged 17.3 mm in length and 13.2 mm in width. Incubation and nestling periods averaged 16 days each. The Southern House Wren on Chiloe Island has a larger clutch size than in the tropics, but a smaller clutch size than populations at the same latitude in the Northern Hemisphere. The Southern House Wren has larger eggs and a longer incubation period but a similar nestling period as House Wrens in the Northern Hemisphere. Received 23 August 2011. Accepted 29 January 2012.
Ecological drivers of group living in two populations of the communally rearing rodent, Octodon degus
(2012) Ebensperger, Luis A.; Sobrero, Raul; Quirici, Veronica; Castro, Rodrigo A.; Ortiz Tolhuysen, Liliana; Vargas, Francisco; Burger, Joseph Robert; Quispe, Rene; Villavicencio, Camila P.; Vasquez, Rodrigo A.; Hayes, Loren D.
Intraspecific variation in sociality is thought to reflect a trade-off between current fitness benefits and costs that emerge from individuals' decision to join or leave groups. Since those benefits and costs may be influenced by ecological conditions, ecological variation remains a major, ultimate cause of intraspecific variation in sociality. Intraspecific comparisons of mammalian sociality across populations facing different environmental conditions have not provided a consistent relationship between ecological variation and group-living. Thus, we studied two populations of the communally rearing rodent Octodon degus to determine how co-variation between sociality and ecology supports alternative ecological causes of group living. In particular, we examined how variables linked to predation risk, thermal conditions, burrowing costs, and food avail-ability predicted temporal and population variation in sociality. Our study revealed population and temporal variation in total group size and group composition that covaried with population and yearly differences in ecology. In particular, predation risk and burrowing costs are supported as drivers of this social variation in degus. Thermal differences, food quantity and quality were not significant predictors of social group size. In contrast to between populations, social variation within populations was largely uncoupled from ecological differences.
Fitness consequences of variation in social group size are not population-specific but are associated with access to food in the communally breeding rodent, Octodon degus
(2024) Hayes, Loren D.; Strom, Madeline K.; Leon, Cecilia; Ramirez-Estrada, Juan; Grillo, Sara; Gao, Cuilan L.; Vasquez, Rodrigo A.; Ebensperger, Luis A.
Studies that concurrently investigate the functional benefits of group living in multiple populations of the same species are rare. Over a 3-year period (2014-2016), we examined two ecologically contrasting populations to test multiple hypotheses for the adaptive significance of group living in the communally breeding rodent Octodon degus. We quantified the size of social units (number of adults, number of adult females), edible vegetation at burrow systems, and per capita offspring weaned (PCOW) in each population. Contrary to expectations, we did not observe population-specific associations between group size and edible vegetation or PCOW nor universal benefits of group living. In one population, PCOW increased in mid-sized groups with more edible vegetation. However, this trend was not consistent across years. Notably, we observed a complete reproductive failure in one population during the first year of study, one that was characterized by low rainfall and no detectable edible vegetation. This result is important because reproductive failure occurred regardless of group size, suggesting that communal living may not buffer degus against the harshest of environmental conditions. Examining how social organization shapes individual reproductive success under extreme variation in food availability is an important step towards understanding how populations will respond to a changing climate.
Geographic Variation in the Association between Exploratory Behavior and Physiology in Rufous-Collared Sparrows
(2012) Maldonado, Karin; van Dongen, Wouter F. D.; Vasquez, Rodrigo A.; Sabat, Pablo
Increasing research has attempted to clarify the links between animal personality and physiology. However, the mechanisms driving this association remain largely unknown, and knowledge of how ecological factors may affect its direction and strength is scant. In this study, we quantified variation in the association between exploratory behavior, basal metabolic rate (BMR), and total evaporative water loss (TEWL) in rufous-collared sparrows (Zonotrichia capensis) inhabiting desert, Mediterranean, and cold-temperate climates. We found that the exploratory behavior score was highest in birds from the cold-temperate site, which was characterized by a moderate level of ecological variability (seasonality). Moreover, the association between exploratory behavior and physiological variables differed among localities. Only birds from the Mediterranean site showed a positive correlation between exploratory behavior and BMR. We found no association between exploration and TEWL at any study site. Our findings suggest that differences in the ecological conditions experienced by each sparrow population result in a particular combination of behavioral and physiological traits. An understanding of this intraspecific variation along ecological gradients provides unique insights into how specific ecological conditions affect the coupling of behavioral and physiological traits and the mechanisms underlying that relationship.
Geographic variation in the repeatability of a personality trait
(2010) van Dongen, Wouter F. D.; Maldonado, Karin; Sabat, Pablo; Vasquez, Rodrigo A.
Animal personalities are interindividual behavioral differences that are consistent across time or contexts. Increasing research is revealing the adaptive significance of personalities, although the mechanisms driving this variation remain largely unknown. A possible source of variation in personality traits is interpopulational differences in the strength of selection acting upon them. The response to selection can be measured indirectly via the behavior's repeatability, as repeatability generally sets an upper limit to trait heritability. However, no information currently exists on geographic variation in personality repeatability. We therefore quantified repeatability in exploratory behavior, a common personality trait, over multiple trials for 3 populations of rufous-collared sparrow (Zonotrichia capensis), focusing on 3 specific measures (exploration speed, diversity of perches visited, and number of hops). We also asked how differences in repeatability of these 3 measures affect other aspects of exploration, such as the temporal consistency of intercorrelations between the measures. Exploration speed was highly repeatable across all populations, whereas diversity was only repeatable in 2 of 3 populations and hopping behavior not at all. These differences in repeatability lead to temporal variation in the correlation matrices of the 3 exploration measures. Finally, only trial number influenced interindividual variability in exploration, whereas population identity, experimental conditions (i.e., conducting the novel environment assay under laboratory or field conditions), and time since capture all had no effect. Our findings highlight the complexity of using measures of behavioral consistency as a definition of personalities and emphasize the value of quantifying interpopulational patterns of trait repeatability.
Haematozoa in forest birds from southern Chile
(2008) Merino, Santiago; Moreno, Juan.; Vasquez, Rodrigo A.; Martinez, Javier; Sanchez-Monsalvez, Inocencia; Estades, Cristian F.; Ippi, Silvina; Sabat, Pablo; Rozzi, Ricardo; Mcgehee, Steven
The existence of latitudinal gradients in species richness and their abundance is known for many free living organisms but few cases have been reported for parasitic diseases. In addition, asymmetries between the Northern and Southern Hemispheres in several characteristics may affect the distribution and diversity of species at all ecological levels. In this respect, we study the distribution of several genera of blood parasites infecting birds along a latitudinal gradient that includes the world's southernmost forests ecosystems. Birds were mist-netted and sampled for blood in localities across Chile ranging from 33 degrees S to 55 degrees S during the years 2003-06. Overall, 26 bird species were sampled and 27 parasite lineages were identified. The latter belonged to three genera: Plasmodium (8), Haemoproteus (8) and Leucocytozoon (11). We found a positive significant relationship between prevalence and latitude for Leucocytozoon lineages and a negative relationship for Haemoproteus, Plasmodium and mixed infections. However, we did not find a significant relationship between parasite diversity and latitude. We found 18 lineages infecting only one species of host, and 19 lineages appear in only one of the localities of sampling. This pattern implies that some parasite lineages may evolve in isolation in some species/localities. In addition, specificity at the host-family level was only found for Haemoproteus lineages infecting birds in the family Emberizidae. Individuals of the long distance migrant bird white-crested elaenia (Elaenia albiceps), were found infected by the same parasite lineages in localities separated by 20 degrees of latitude. Infections by these lineages were detected in other sedentary birds including juveniles and nestlings of different bird species. Therefore, long distance migrants are able to distort the presence of latitudinal gradients of diseases due to the potential role of migrants in spreading infections. Geographical gradients in prevalence of avian haematozoa differ between parasite genera and hemispheres, probably in relation to the existence of appropriate vector-parasite-host interactions.
Individual behavioural variation does not affect social organization or reproductive success in a cooperative small mammal
(2024) van der Marel, Annemarie; Johnson, Nicholas E.; Grillo, Sara; Riquelme, Juan; Vasquez, Rodrigo A.; Gillam, Erin H.; Ebensperger, Luis A.; Hayes, Loren D.
Recent evidence indicates that individual behavioural variation in animals, defined as consistent individual differences in behaviour across contexts and time, influence ecological and evolutionary processes, and a growing number of studies demonstrate that individual behavioural variation can play a large role in shaping grouping dynamics among social animals. We studied the common degu, Octodon degus, a social rodent, to evaluate whether individual behavioural variation underlies social organization and the reproductive success of individuals within groups. We examined social groups in a population in central-north Chile during one breeding season, tested 67 adults in an open field test (i.e., the propensity to explore an unfamiliar environment) and 62 adults in determined assortment based on individual behavioural differences across 19 social groups, and performed genetic analyses to assess reproductive success. We found that the response to the poke test was repeatable, while none of the behaviours from an open field test were. The repeatable behaviour during the poke test was not associated to components of social organization (group composition), or to reproductive success. These findings imply that individual behavioural varia- tion did not affect grouping patterns or direct fitness in this degu population.
Intraspecific variation in exploratory behavior and elevational affinity in a widely distributed songbird
(SPRINGER, 2018) Poblete, Yanina; Gutierrez, Victor; Cid, Valeska; Newsome, Seth D.; Sabat, Pablo; Vasquez, Rodrigo A.
Populations of the same species can vary substantially in their behavioral and morphometric traits when they are subject to different environmental pressures, which may lead to the development of different adaptive strategies. We quantified variation in exploratory behavior and morphometric traits among two rufous-collared sparrow populations that occur at low and high elevations in central Chile. Moreover, we used census and delta H-2 values of feather and blood to evaluate migration. We found that individual sparrows inhabiting high elevations were larger and showed more intense exploratory behavior in comparison with those that were captured at lower elevation. Moreover, we observed a steady decline in sparrow abundance during the winter and similar delta H-2 values for blood collected in the winter and summer at this site, which were significantly lower than blood delta H-2 values observed at low elevation. This pattern suggests that individuals do not move long distances during winter, and likely they remain at similar elevations in refuge habitats. As predicted, our results support the existent of different adaptive strategies among populations of the same species, and suggest that the combination of behavioral, morphometric, and stable isotope data is a novel and robust integrative approach to assess differences in adaptation across environmental gradients.
Molecular characterization of an ancient Hepatozoon species parasitizing the 'living fossil' marsupial 'Monito del Monte' Dromiciops gliroides from Chile
(2009) Merino, Santiago; Vasquez, Rodrigo A.; Martinez, Javier; Luis Celis-Diez, Juan; Gutierrez-Jimenez, Leticia; Ippi, Silvina; Sanchez-Monsalvez, Inocencia; Martinez-de la Puente, Josue
The Microbiotheriid Dromiciops gliroides, also known as 'Monito del Monte', is considered to be a threatened species and the only living representative of this group of South American marsupials. During the last few years, several blood samples from specimens of 'Monito del Monte' captured at Chiloe island in Chile have been investigated for blood parasites. Inspection of blood smears detected a Hepatozoon species infecting red blood cells. The sequences of DNA fragments corresponding to small subunit ribosomal RNA gene revealed two parasitic lineages belonging to Hepatozoon genus. These parasite lineages showed a basal position with respect to Hepatozoon species infecting rodents, reptiles, and amphibians but are phylogenetically distinct from Hepatozoon species infecting the order Carnivora. In addition, the Hepatozoon lineages infecting D. gliroides are also different from those infecting other micro-mammals living in sympatry, as well as from some that have been described to infect an Australian species of bandicoot. The potential vector of this parasite appears to be the host-specific tick Ixodes neuquenensis because the sequencing of a long amplicon determined the presence of one of the two lineages found in the marsupial. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 568-576.
Morphological description of the White-throated treerunner (Pygarrhichas albogularis, King 1831) in the Cape Horn Biosphere Reserve, Chile
(2024) Novoa Galaz, Fernando Javier; Jara Millar, Rocio; Barroso, Omar; Altamirano Oyarzun, Tomas Alberto; Ibarra Eliessetch, José Tomas; Rivero De Aguilar, Juan; Vasquez, Rodrigo A.; Rozzi, Ricardo
La ecorregión subantártica de Magallanes constituye una de las áreas silvestres más prístinas y alberga los ecosistemas boscosos más australes del mundo, que están protegidos por la Reserva de la Biosfera Cabo de Hornos (RBCH), Chile. En estos bosques, las aves son el grupo de vertebrados con mayor número de especies. Sin embargo, aspectos esenciales de la ecología y la morfología de varias especies de esta región todavía han sido poco investigados. Entre estas especies, se incluye el comesebo grande (Pygarrhichas albogularis, King 1831), considerado un “fósil viviente” por ser la única especie viva del género Pygarrhichas. Además, es un furnariido endémico de los bosques templados de Sudamérica. Utilizando la base de datos de 23 años del Programa de Investigación Ornitológica a Largo Plazo del Parque Omora (54º56’S, 67º38’W), que ha realizado capturas y anillamientos de aves de bosque, describimos la morfología, longevidad y presencia del comesebo grande en la RBCH. Entre los años 2000 y 2022 se anillaron 91 individuos, incluyendo 29 recapturas que nos permitieron determinar que esta especie puede vivir al menos cinco años. Las medidas morfométricas mostraron una correlación positiva entre las medidas de pico y la longitud del tarso con las longitudes de la cola y del ala. El peso varió en cada estación anual, pero no significativamente. La mayor presencia al interior del bosque antiguo sugiere una dependencia de esta especie con los grandes árboles. Este estudio amplía el conocimiento sobre la historia natural del comesebo grande, particularmente de sus poblaciones que habitan en los bosques más australes del mundo.
Octodon degus kin and social structure
(2016) Davis, Garrett T.; Vasquez, Rodrigo A.; Poulin, Elie; Oda, Esteban; Bazan Leon, Enrique A.; Ebensperger Pesce, Luis Alberto; Hayes, Loren D.
On the relationship between sugar digestion and diet preference in two Chilean avian species belonging to the Muscicapoidea superfamily
(2006) Gatica, Carolina D. L.; Gonzalez, Sandra P.; Vasquez, Rodrigo A.; Sabat, Pablo
It has been hypothesized that species belonging to the Sturnidae-Muscicapidae lineage, despite having generalist diets comprising fruits with sugars of diverse kinds, do not express intestinal sucrase. In order to increase the taxonomical range of species for which sucrase intestinal activity has been investigated, we analyzed the relationship between enzymatic activity (sugar digestion) and feeding preference for native fruits containing sucrose, in two South American members of the superfamily Muscicapoidea, the Austral thrush (Turdus falcklandii) and the Chilean mockingbird (Mimus thenca). We hypothesized that these birds would lack intestinal sucrase activity and that in preference tests they would reject sucrose solutions. Both thrushes and mockingbirds lacked significant intestinal sucrase activity. Considering the phylogenetic constraint hypothesis for sucrose digestion in the Muscicapoidea superfamily, our results support the notion that lack of sucrase activity is a shared derived-character only for the Cinclidae-Sturnidae-Turdinae lineage, and suggests that the selective pressure that these birds can exert on the plants whose seeds they disperse and whose flowers they visit are consistent across world hemispheres. Food preference by thrushes was significantly biased toward glucose and fructose, showing scant to nil consumption of sucrose, thus corroborating a positive relationship between digestion capabilities and food preference for different sugar types.
Survival rates in the world's southernmost forest bird community
(2023) Sandvig, Erik M.; Quilodran, Claudio S.; Altamirano, Tomas A.; Aguirre, Francisco; Barroso, Omar; de Aguilar, Juan Rivero; Schaub, Michael; Kery, Marc; Vasquez, Rodrigo A.; Rozzi, Ricardo
The Magellanic sub-Antarctic Forest is home to the world's southernmost avian community and is the only Southern Hemisphere analogue to Northern Hemisphere temperate forests at this latitude. This region is considered among the few remaining pristine areas of the world, and shifts in environmental conditions are predominantly driven by climate variability. Thus, understanding climate-driven demographic processes is critical for addressing conservation issues in this system under future climate change scenarios. Here, we describe annual survival patterns and their association with climate variables using a 20-year mark-recapture data set of five forest bird species in the Cape Horn Biosphere Reserve. We develop a multispecies hierarchical survival model to jointly explore age-dependent survival probabilities at the community and species levels in a group of five forest passerines. At the community level, we assess the association of migratory behavior and body size with survival, and at the species level, we investigate the influence of local and regional climatic variables on temporal variations of survival. We found a positive effect of precipitation and a negative effect of El Nino Southern Oscillation on juvenile survival in the white-crested Elaenia and a consistent but uncertain negative effect of temperature on survival in juveniles and 80% of adults. We found only a weak association of climate variables with survival across species in the community and no temporal trends in survival for any of the species in either age class, highlighting apparent stability in these high austral latitude forests. Finally, our findings provide an important resource of survival probabilities, a necessary input for assessing potential impacts of global climate change in this unique region of the world.

Browsing by Author "Vasquez, Rodrigo A."

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