Daniela S. Rivera

Direct fitness of group living mammals varies with breeding strategy, climate and fitness estimates

1. Understanding how variation in fitness relates to variation in group living remains critical to determine whether this major aspect of social behaviour is currently adaptive. 2. Available evidence in social mammals aimed to examine this issue remains controversial. Studies show positive (i.e. potentially adaptive), neutral or even negative fitness effects of group living. 3. Attempts to explain this variation rely on intrinsic and extrinsic factors to social groups. Thus, relatively more positive fitness effects are predicted in singularly breeding as opposed to plural breeding species. Fitness effects of sociality in turn may depend on ecological conditions (i.e. extrinsic factors) that influence associated benefits and costs. 4. We used meta-analytic tools to review how breeding strategy or ecological conditions influence the effect size associated with direct fitness-sociality relationships reported in the mammalian literature. Additionally, we determined how taxonomic affiliation of species studied, different fitness and sociality measures used, and major climatic conditions of study sites explained any variation in direct fitness effect size. 5. We found group living had modest, yet positive effects on direct fitness. This generally adaptive scenario was contingent not only upon breeding strategy and climate of study sites, but also on fitness measures examined. Thus, positive and significant effects characterized singular as opposed to plural breeding strategies. 6. We found more positive fitness effects on studies conducted in tropical as opposed to temperate or arid climates. More positive and significant effects were noted on studies that relied on group fecundity, male fecundity and offspring survival as measures of fitness. 7. To conclude, direct fitness consequences of mammalian group living are driven by interspecific differences in breeding strategy and climate conditions. Other factors not examined in this study, namely individual variation in direct and indirect fitness benefits and potential interactions between social and ecological conditions, may be important and require further studies.

Age Progression of Neuropathological Markers in the Brain of the Chilean Rodent Octodon degus, a Natural Model of Alzheimer's Disease

Alzheimers disease (AD) is the most common neurodegenerative disorder and the leading cause of age‐related dementia worldwide. Several models for AD have been developed to provide information regarding the initial changes that lead to degeneration. Transgenic mouse models recapitulate many, but not all, of the features of AD, most likely because of the high complexity of the pathology. In this context, the validation of a wild‐type animal model of AD that mimics the neuropathological and behavioral abnormalities is necessary. In previous studies, we have reported that the Chilean rodent Octodon degus could represent a natural model for AD. In the present work, we further describe the age‐related neurodegeneration observed in the O. degus brain. We report some histopathological markers associated with the onset progression of AD, such as glial activation, increase in oxidative stress markers, neuronal apoptosis and the expression of the peroxisome proliferative‐activated receptor γ coactivator‐1α (PGC‐1α). With these results, we suggest that the O. degus could represent a new model for AD research and a powerful tool in the search for therapeutic strategies against AD.

On cognitive ecology and the environmental factors that promote Alzheimer disease: lessons from Octodon degus (Rodentia: Octodontidae)

Cognitive ecologist posits that the more efficiently an animal uses information from the biotic and abiotic environment, the more adaptive are its cognitive abilities. Nevertheless, this approach does not test for natural neurodegenerative processes under field or experimental conditions, which may recover animals information processing and decision making and may explain, mechanistically, maladaptive behaviors. Here, we call for integrative approaches to explain the relationship between ultimate and proximate mechanisms behind social behavior. We highlight the importance of using the endemic caviomorph rodent Octodon degus as a valuable natural model for mechanistic studies of social behavior and to explain how physical environments can shape social experiences that might influence impaired cognitive abilities and the onset and progression of neurodegenerative disorders such as Alzheimer disease. We consequently suggest neuroecological approaches to examine how key elements of the environment may affect neural and cognitive mechanisms associated with learning, memory processes and brain structures involved in social behavior. We propose the following three core objectives of a program comprising interdisciplinary research in O. degus, namely: (1) to determine whether diet types provided after weaning can lead to cognitive impairment associated with spatial memory, learning and predisposing to develop Alzheimer disease in younger ages; (2) to examine if early life social experience has long term effects on behavior and cognitive responses and risk for development Alzheimer disease in later life and (3) To determine if an increase of social interactions in adult degu reared in different degree of social stressful conditions alter their behavior and cognitive responses.

Sociality of Octodontomys gliroides and other octodontid rodents reflects the influence of phylogeny

Abstract Multiple ecological factors are known to drive variation in social behavior. However, group-living in some species appears to be highly conserved, suggesting a phylogenetic influence. In this study, we evaluated both scenarios using intraspecific and interspecific comparisons across octodontid rodents. We first examined 2 different populations of Andean degu (Octodontomys gliroides), representing 2 extremes of a climate vegetation gradient across the Andes range. We evaluated how ecological variation in terms of abundance and distribution of food resources, predation risk, and burrowing costs predicted interpopulation variation in group size and range-area overlap (2 proxies of sociality). We estimated these measures of sociality from livetrapping and radiotelemetry. We then used phylogenetic methods to determine whether sociality exhibits a phylogenetic signal and reconstructed the ancestral state of sociality across the family Octodontidae. Overall activity of females and males of O. gliroides was greater during nighttime than daytime. Across populations we found significant differences in ecology, including abundance and distribution of food, predation risk, and burrowing costs. However, populations were similar in terms of group size and range-area overlap. The phylogenetic approach revealed a strong and significant phylogenetic signal associated with sociality, where this behavior was present early during the evolution of octodontid rodents. Together, these findings imply that sociality of O. gliroides is not linked to current population differences in ecology. Resumen La variación en la conducta social ha sido atribuida a múltiples factores ecológicos. Sin embargo, la vida en grupo en algunas especies es un rasgo altamente conservado, sugiriendo una influencia filogenética. En este estudio, se evaluó ambos escenarios usando comparaciones intraespecíficas e interespecíficas a través de roedores octodóntidos. En primer lugar se evaluaron 2 poblaciones de degu Andino (Octodontomys gliroides) que representan 2 extremos de un gradiente climático y de vegetación a través de la Cordillera de los Andes. Se evaluó como la variación en términos de abundancia y distribución de recursos alimenticios, riesgo de depredación, y costos asociados a cavar madrigueras podrían predecir la variación interpoblacional en tamaño de grupo y solapamiento del ámbito de hogar (2 medidas de sociabilidad). Estas medidas fueron estimadas con datos de trampeo y radiotelemetría. Además, se utilizaron métodos filogenéticos para determinar si el rasgo social presenta señal filogenética, y de esta manera reconstruir el estado ancestral de la sociabilidad a través de la familia Octodontidae. Se encontraron diferencias estadísticamente significativas entre las poblaciones en términos de ecología, incluyendo abundancia y distribución de recursos alimenticios, riesgo de depredación, costos asociados a cavar madrigueras. Sin embargo, el tamaño de grupo y solapamiento del ámbito de hogar fueron similares entre ambas poblaciones. El análisis filogenético reveló una fuerte y significativa señal filogenética asociada a la sociabilidad, y que esta conducta estuvo presente temprano en la evolución de los roedores octodóntidos. En conjunto, estos resultados implican que la vida en grupo en O. gliroides no está relacionada a las diferencias en ecología en las poblaciones actuales.

Legal and Institutional Framework of Water Resources

The water sector in Chile underwent major changes as a result of decentralization and market reforms. The Water Code of 1981 is the main regulation governing terrestrial water use and water rights (WR) in Chile. Water is national property for public use. However, the Water Code grants permanent and transferable WR to individuals in order to achieve an efficient allocation of water through market transactions of water rights. Once water rights have been granted, they fall under the jurisdiction of private civil law, rather than administrative law. This chapter provides an overview of legal water regime in Chile, based on the review of six central topics: normative framework; regulatory model and legal nature of waters; origin of water rights; water management and administration; groundwater regime; and, finally, the most common conflicts that occur in the sector. On this basis, and considering legal and jurisprudential elements, we identify the defining features of Chile’s Water Law, which mixes powers of a centralized State Administration, market tools and water user organizations.

Fog collection and its relationship with local meteorological variables in a semiarid zone in Chile

In semiarid and arid zones, fog is considered an important alternative water source. The Southeast Pacific anticyclone and the cold Humboldt Current that characterize the north of Chile promote the formation of stratocumulus along the coastline. The thermally induced winds move these clouds eastwards favoring the formation of fog in the high hills of the Coast Range. The goal of this work is to characterize the fog water collected by a standard fog collector and its relationship with local meteorological variables. We found that the collected water is seasonally dependent, larger in summer than in winter. The mean diurnal cycle in autumn, summer and winter presents two maxima, at the early morning and late afternoon, meanwhile in winter it presents smooth variations during the day. The wind regime was compatible with land-sea circulation. The monthly mean temperature reached the maximum value in March and the minimum value between July and September, whereas the mean monthly daily temperature amplitude was larger in winter than in summer. The minimum values of relative humidity were achieved in the winter months. The fog water collection varies from zero to a maximum value that increased with wind speed, and mainly occurred with SW and NE winds. The fog index (FI) was defined as the percentage of foggy-days per month for which the water collected is greater than one liter. We found that FI follows the same trend as the monthly collected water, and decreases with the mean monthly daily temperature amplitude.