First Detection of Benign Rabbit Caliciviruses in Chile

Pathogenic lagoviruses (Rabbit hemorrhagic disease virus, RHDV) are widely spread across the world and are used in Australia and New Zealand to control populations of feral European rabbits. The spread of the non-pathogenic lagoviruses, e.g., rabbit calicivirus (RCV), is less well studied as the infection results in no clinical signs. Nonetheless, RCV has important implications for the spread of RHDV and rabbit biocontrol as it can provide varying levels of cross-protection against fatal infection with pathogenic lagoviruses. In Chile, where European rabbits are also an introduced species, myxoma virus was used for localised biocontrol of rabbits in the 1950s. To date, there have been no studies investigating the presence of lagoviruses in the Chilean feral rabbit population. In this study, liver and duodenum rabbit samples from central Chile were tested for the presence of lagoviruses and positive samples were subject to whole RNA sequencing and subsequent data analysis. Phylogenetic analysis revealed a novel RCV variant in duodenal samples that likely originated from European RCVs. Sequencing analysis also detected the presence of a rabbit astrovirus in one of the lagovirus-positive samples.

Living with voracious roommates: Factors that explain isotopic niche variation in a mixed colony of insectivorous bats

Theory predicts that in resource-limited environments, coexisting species may overlap their niche dimensions but must differ in at least one to avoid competitive exclusion. Specifically, it has been suggested that the coexistence of competing species within a guild, could be sustained with mechanisms of resource partitioning, such as segregation along a trophic dimension. Among the most gregarious mammals are bats, which present diversification in their diet based on habitat choice and body size. Despite differences that could explain specialization in prey selection, there are insufficient studies that explore food overlap in mixed bat colonies and the factors that determine the selection of prey, both at intra- and inter-specific levels. To fill this gap, we analyzed the isotope signal (δ13C and δ15N) in feces collected in a mixed colony of Tadarida brasiliensis and Myotis chiloensis. To understand how several factors could influence these isotopic signals, intrinsic explanatory variables were analyzed, including body mass, body length, age, and sex. Also, extrinsic variables were analyzed, including monthly temporality and moonlight intensity. Our findings support age-dependent specialization in M. chiloensis, with a significant role of moonlight intensity and sex on δ15N. In T. brasiliensis, we identified a significant effect of size, sex, and ear length on δ15N. Our analysis indicates that both species of bats experience diverse degrees of overlap through austral summer months, affected by several factors that explain the variability in their fecal isotopic signals.

Covariation of taxonomic and functional facets of β-diversity in Chilean freshwater fish assemblages: Implications for current and future processes of biotic homogenization

The biodiversity of assemblages that experience the introduction and extinction of species may lead to responses in two important facets: The taxonomic and functional diversity. The way in which these facets are associated may reveal important implications and consequences for the conservation of those assemblages. Considering the critical situation of freshwater fishes in continental Chile (30° - 56° S), we analyzed how the taxonomic (TDβ) and functional (FDβ) facets of β-diversity, and their components of turnover and nestedness, are associated. We evaluated changes in β-diversity (ΔTDβ and ΔFDβ), turnover (ΔTDtur and ΔFDtur), and nestedness (ΔTDnes and ΔFDnes) in 20 fish assemblages from their historical (pre-European) to current composition. We also simulated future trends of these changes, assuming that native species with conservation issues would become extinct. Our results show that the fish assemblages studied are in a process of loss of β-diversity, both in taxonomic and functional facets (ΔTDβ = -3.9%; ΔFDβ = -30.4%); also, that these facets are positively correlated in the assemblages studied (r = 0.617; P < 0.05). Both components showed by loss in nestedness (ΔTDnes = -36.9%; ΔFDnes = -60.9%) but gain in turnover (ΔTDtur = 9.2%; ΔFDtur = 12.3%). The functional β-diversity decreased more than the taxonomic (ΔFDβ > ΔTDβ), which was caused chiefly by six exotic species of Salmonidae, whose geographical spread was wider and that at the same time shared several morpho-functional traits. Our forecasts, assuming an intensification in the extinction of Endangered and Vulnerable native species, indicate that the process of homogenization will continue, though at a lower rate. Our study shows that the freshwater ichthyofauna of continental Chile is undergoing biotic homogenization, and that this process involves the facets of taxonomic and functional β-diversity, which are show high correlation between historical and current compositions. Both facets show that process is influenced by nestedness, and while turnover contributes to differentiation (both taxonomic and functional), its importance is overshadowed by nestedness.

World-level ecologists in Chile: Oldtimers, newcomers, and the bypassed

Background

A team of 3 scientometrists led by John Ioannidis published in 2020 an extensive and updated database (ca. 6.9 million researchers in 22 disciplines and 176 sub-disciplines), ordering them according to a composite bibliometric index that measures their whole trajectory (career-long) impact and their annual impact at year 2019. They reported the top 100,000 scientists (1.45% across all disciplinary fields) or the top 2% of each subfield discipline, thus publishing the ranking of ca. 150,000 researchers worldwide.

Methods and findings

We filtered that information for the disciplinary and sub-disciplinary areas corresponding to Ecology and identified a total of 14 ecologists with residence in Chile that appear in either of those two worldwide rankings. We report their measured productivity as both whole trajectory (career-long) and as annual impact at year 2019. We attribute their high registered productivity to their training at the doctoral level in prestigious foreign universities, their academic positions in internationally recognized Chilean universities, and their participation in state-funded research centers of scientific excellence. Exceptions to the rule are presented.

Conclusions

The 14 ecologists identified with the scientometric algorithm proposed by Ioannidis and coworkers include, but are not restricted, to the most cited ecologists in Chile. We put forth possible reasons for some puzzling omissions from these rankings.

Are Latin American ecologists recognized at the world level? A global comparison

Background

Ioannidis et al. (2020) reported a standardized estimate of scientific productivity obtained from a worldwide database of 6,880,389 scientists who published at least 5 papers picked up by the Scopus database, and elaborated a ranking of ca. 120,000 scientists by both whole trajectory (career-long) impact and their current impact at year 2019. The goal of our paper is to contextualize Latin American ecologists’ contribution at the world level based on the four most scientifically productive countries in the region.

Methods and findings

Ioannidis et al. (2020) proposed a composite index that is the sum of six scientometric indicators: (1) The number of allocites, (2) the h index, (3) a per capita corrected version of h, (4) the allocites received as single author, (5) those received as single + first author, and (6) those as single + first + last author. We selected data for ecologists from Argentina, Brazil, Chile, and Mexico and comparatively analyzed their productivity according to the proposed index. We also compared these data with those obtained from a global sample of the top ecologists worldwide.

Conclusions

Based on Ioannidis et al.’s proposition to evaluate scientific productivity we extract three lessons: (1) It does not pay to publish many papers; what counts is the number of allocites (i.e., self-citations do not add up). (2) Either be single, first, or last author; it does not pay to be in the middle of an authorship line. (3) Even worse it is to be among many co-authors because the proposed index allocates credits on a per capita basis.

Few self-citations among Chilean ecologists

Background

We determine the occurrence of self-citations among 36 Chilean ecologists with the highest h index values recorded in Web of Science. Because the practice of self-citation is perceived as negative by inflating a given researcher’s impact factor, we evaluate if those ecologists (five of them having been awarded the National Prize in Natural Sciences) tend unduly to self-citation, or alternately, receive citations from others ostensibly because their peers recognize their theoretical and empirical output.

Methods and findings

We use a recently proposed self-citation estimate easily calculated from h index values recorded in the restricted-access Web of Science (Wos) database and the open-access Google Scholar’s (GS) Researcher Profiles and compare these metrics.

Conclusions

The Chilean ecologists showed low self-citation values, independently of their status as National Prize awardees. Their publications were highly cited by unrelated peers, likely on account of their novelty or quality. Among middle-aged (50–60 year) and young (< 50 year) Chilean ecologists open-access GS h index values are significantly correlated with those from WoS, thus rendering expeditious this method of citation assessment.

Latitudinal patterns in the diet of Andean condor (Vultur gryphus) in Chile: Contrasting environments influencing feeding behavior

Human-dominated environments alter the availability and quality of resources for many species, especially for scavengers that have large home ranges and plastic foraging behaviors that enable them to exploit novel resources. Along the western slope of the Andes, the modification of natural landscapes have resulted in significant declines in native prey, the introduction of non-native species, and an increase in the availability of anthropogenic resources. These factors have likely influenced the resources available to Andean condors (Vultur gryphus), however, data are lacking as to how condor's diet vary along their large latitudinal range. We evaluated differences in Andean condor diet along a ~2500 km latitudinal gradient in Chile from the heavily modified Central zone (32-34°S) to the more pristine Austral zone (44-56°S). We assessed diet composition through the identification of prey remains in condor pellets, and carbon and nitrogen isotope analysis of condor feathers and their primary prey identified from pellet analysis. Our results identified medium- and large-bodied domesticated mammals (ungulates) and introduced exotic species (lagomorphs) as common prey across the study area. Condors from the Central zone had the largest isotopic niche width, probably related to consumption of anthropogenic resources with distinctly high carbon isotope values indicative of C₄-based foods likely acquired from landfills or corn-fed livestock. Isotopic niches for condors from the Southern and Austral zones almost completely overlapped. Andean condor diet is strongly influenced by local conditions determining differential access to prey sources. The high dependence of Andean condors on livestock across a large geographical area, and landfills in more (sub)urban areas, may help stabilize their populations via anthropogenic resources subsidies. Long-term dependence on such resources, however, may have health costs including contaminant exposure and greater mortality risk. These data will help identify potential threats related to resource availability and use, and better inform management and conservation decisions.

Extreme climatic events change the dynamics and invasibility of semi-arid annual plant communities

Extreme climatic events represent disturbances that change the availability of resources. We studied their effects on annual plant assemblages in a semi-arid ecosystem in north-central Chile. We analysed 130 years of precipitation data using generalised extreme-value distribution to determine extreme events, and multivariate techniques to analyse 20 years of plant cover data of 34 native and 11 exotic species. Extreme drought resets the dynamics of the system and renders it susceptible to invasion. On the other hand, by favouring native annuals, moderately wet events change species composition and allow the community to be resilient to extreme drought. The probability of extreme drought has doubled over the last 50 years. Therefore, investigations on the interaction of climate change and biological invasions are relevant to determine the potential for future effects on the dynamics of semi-arid annual plant communities.

Low functional richness and redundancy of a predator assemblage in native forest fragments of Chiloe island, Chile

1. Changes in land use and habitat fragmentation are major drivers of global change, and studying their effects on biodiversity constitutes a major research programme. However, biodiversity is a multifaceted concept, with a functional component linking species richness to ecosystem function. Currently, the interaction between functional and taxonomic components of biodiversity under realistic scenarios of habitat degradation is poorly understood. 2. The expected functional richness (FR)-species richness relationship (FRSR) is positive, and attenuated for functional redundancy in species-rich assemblages. Further, environmental filters are expected to flatten that association by sorting species with similar traits. Thus, analysing FRSR can inform about the response of biodiversity to environmental gradients and habitat fragmentation, and its expected functional consequences. 3. Top predators affect ecosystem functioning through prey consumption and are particularly vulnerable to changes in land use and habitat fragmentation, being good indicators of ecosystem health and suitable models for assessing the effects of habitat fragmentation on their FR. 4. Thus, this study analyses the functional redundancy of a vertebrate predator assemblage at temperate forest fragments in a rural landscape of Chiloe island (Chile), testing the existence of environmental filters by contrasting an empirically derived FRSR against those predicted from null models, and testing the association between biodiversity components and the structure of forest fragments. 5. Overall, contrasts against null models indicate that regional factors determine low levels of FR and redundancy for the vertebrate predator assemblage studied, while recorded linear FRSR indicates proportional responses of the two biodiversity components to the structure of forest fragments. Further, most species were positively associated with either fragment size or shape complexity, which are highly correlated. This, and the absence of ecological filters at the single-fragment scale, rendered taxonomically and functionally richer predator assemblages at large complex-shaped fragments. 6. These results predict strong effects of deforestation on both components of biodiversity, potentially affecting the functioning of remnants of native temperate forest ecosystems. Thus, the present study assesses general responses of functional and taxonomic components of biodiversity to a specific human-driven process.

Effects of functional constraints and opportunism on the functional structure of a vertebrate predator assemblage

1. Within mainstream ecological literature, functional structure has been viewed as resulting from the interplay of species interactions, resource levels and environmental variability. Classical models state that interspecific competition generates species segregation and guild formation in stable saturated environments, whereas opportunism causes species aggregation on abundant resources in variable unsaturated situations. 2. Nevertheless, intrinsic functional constraints may result in species-specific differences in resource-use capabilities. This could force some degree of functional structure without assuming other putative causes. However, the influence of such constraints has rarely been tested, and their relative contribution to observed patterns has not been quantified. 3. We used a multiple null-model approach to quantify the magnitude and direction (non-random aggregation or divergence) of the functional structure of a vertebrate predator assemblage exposed to variable prey abundance over an 18-year period. Observed trends were contrasted with predictions from null-models designed in an orthogonal fashion to account independently for the effects of functional constraints and opportunism. Subsequently, the unexplained variation was regressed against environmental variables to search for evidence of interspecific competition. 4. Overall, null-models accounting for functional constraints showed the best fit to the observed data, and suggested an effect of this factor in modulating predator opportunistic responses. However, regression models on residual variation indicated that such an effect was dependent on both total and relative abundance of principal (small mammals) and alternative (arthropods, birds, reptiles) prey categories. 5. In addition, no clear evidence for interspecific competition was found, but differential delays in predator functional responses could explain some of the unaccounted variation. Thus, we call for caution when interpreting empirical data in the context of classical models assuming synchronous responses of consumers to resource levels.

On the relationship between productivity and food chain length at different ecological levels

The effects of energy on food web structure have been debated for at least 80 years. Nevertheless, the empirical evidence is meager, especially from terrestrial ecosystems. We analyzed long-term temporal variation in food chain length in a semiarid continental ecosystem, where productivity shows large interannual variations. Incidence of nonherbivorous prey in predator diet was used as a proxy of trophic position, allowing us to analyze the effect of productivity on food chain length within the assemblage of top predators (which comprises the most abundant and persistent top predators in the system) and to compare observed patterns at the species and assemblage levels. At the species level, the relationship between trophic position and productivity took different forms, varying in magnitude and shape. This pattern contrasts with the consistent increase in food chain length, with productivity observed at the assemblage level. Our results indicate that productivity can be a main determinant of food chain length, but not necessarily because of energy limitation. Further, the increase in food chain length with available energy probably represents an aggregate attribute, driven to a large extent by predators with higher consumption rates, rather than being the result of compensatory responses among predators.

Interplay between metabolic rate and diet quality in the South American fox, Pseudalopex culpaeus

We studied the metabolic costs associated with the ingestion of peppertree fruits (Schinus molle) in the culpeo fox, Pseudalopex culpaeus, the second largest canid in South America. Throughout its range of distribution, this fox feeds on rodents and other small vertebrates, and also on peppertree fruits, which represent 98% of total fruits consumed in semiarid Chile. Peppertree contains a high diversity of phytochemicals. Foxes feeding on diets containing rats and peppertree fruits (mixed diets) exhibited a 98.9% increase in basal rate of metabolism when compared to rat-acclimated foxes. Thus, acute ingestion of chemically defended fruits has an energetic cost for the fox, reflected in higher values of basal metabolism. Increased metabolic rates may be associated with increased protein synthesis for detoxification and for tissue repair, including the production of biotransformation enzymes.

Population dynamics of a South American rodent: seasonal structure interacting with climate, density dependence and predator effects

Understanding the role of interactions between intrinsic feedback loops and external climatic forces is one of the central challenges within the field of population ecology. For rodent dynamics, the seasonal structure of the environment necessitates changes between two stages: reproductive and non-reproductive. Nevertheless, the interactions between seasonality, climate, density dependence and predators have been generally ignored. We demonstrate that direct climate effects, the nonlinear effect of predators and the nonlinear first-order feedback embedded in a seasonal structure are key elements underlying the large and irregular fluctuations in population numbers exhibited by a small rodent in a semi-arid region of central Chile. We found that factors influencing population growth rates clearly differ between breeding and non-breeding seasons. In addition, we detected nonlinear density dependencies as well as nonlinear and differential effects of generalist and specialist predators. Recent climatic changes may account for dramatic perturbations of the rodent's population dynamics. Changes in the predator guild induced by climate are likely to result, through the food web, in a large impact on small rodent demography and population dynamics. Assuming such interactions to be typical of ecological systems, we conclude that appropriate predictions of the ecological consequences of climate change will depend on having an in-depth understanding of the community-weather system.

Demography and population dynamics of the mouse opossum (Thylamys elegans) in semi-arid Chile: seasonality, feedback structure and climate

Here we present, to the authors' knowledge for the very first time for a small marsupial, a thorough analysis of the demography and population dynamics of the mouse opossum (Thylamys elegans) in western South America. We test the relative importance of feedback structure and climatic factors (rainfall and the Southern Oscillation Index) in explaining the temporal variation in the demography of the mouse opossum. The demographic information was incorporated into a stage-structured population dynamics model and the model's predictions were compared with observed patterns. The mouse opossum's capture rates showed seasonal (within-year) and between-year variability, with individuals having higher capture rates during late summer and autumn and lower capture rates during winter and spring. There was also a strong between-year effect on capture probabilities. The reproductive (the fraction of reproductively active individuals) and recruitment rates showed a clear seasonal and a between-year pattern of variation with the peak of reproductive activity occuring during winter and early spring. In addition, the fraction of reproductive individuals was positively related to annual rainfall, while population density and annual rainfall positively influenced the recruitment rate. The survival rates were negatively related to annual rainfall. The average finite population growth rate during the study period was estimated to be 1.011 +/- 0.0019 from capture-recapture estimates. While the annual growth rate estimated from the seasonal linear matrix models was 1.026, the subadult and adult survival and maturation rates represent between 54% (winter) and 81% (summer) of the impact on the annual growth rate.

Extinction and colonization processes in subpopulations of five neotropical small mammal species

We report the extinction and colonization rates of five sympatric small mammal species at a semiarid locality in north central Chile. We provide information based on 6 years of monitoring on how colonization and extinction rates change according to landscape features (slope aspect) and on their relationship to populations size, population variability, and body size. We found that: (1) for all species in the assemblage, extinction rates of subpopulations from equatorial-facing slopes were significantly lower than those in polar-facing slopes, (2) population size was the most important factor determining extinction rates, (3) colonization rates did not vary between slopes, and were affected by population size only in equatorial-facing slopes, and (4) most species had higher extinction than colonization rates. Persistence of the metapopulation system for all five small mammal species appears to be fueled by repeated colonization events.