Andrés Valenzuela Sánchez

• Research Fellow in Wildlife Health at Zoological Society of London

Background: Body size variation has played a central role in biogeographical research, however, most studies have aimed to describe trends rather than search for underlying mechanisms. In order to provide a more comprehensive understanding of the causes of intra-specific body size variation in ectotherms, we evaluated eight hypotheses proposed in...

The decline of wildlife populations due to emerging infectious disease often shows a common pattern: the parasite invades a naive host population, producing epidemic disease and a population decline, sometimes with extirpation. Some susceptible host populations can survive the epidemic phase and persist with endemic parasitic infection. Understandi...

Forest management can be used to increase the local abundance of species of conservation concern. To achieve this goal, managers must be sure that the relationships between the targeted forest attributes and the focal species abundance are based on robust data and inference. This is a critical issue as the same forest attributes could have opposing...

When facing an emerging infectious disease of conservation concern, we often have little information on the nature of the host-parasite interaction to inform management decisions. However, it is becoming increasingly clear that the life-history strategies of host species can be predictive of individual and population-level responses to infectious d...

Compensatory recruitment is a key demographic mechanism that has allowed the coexistence of populations of susceptible amphibians with Batrachochytrium dendrobatidis (Bd), a fungus causing one of the most devastating emerging infectious disease ever recorded among vertebrates. However, the underlying processes (e.g. density‐dependent increase in su...

Selection, dispersal and drift jointly contribute to generating variation in microbial composition within and between hosts, habitats and ecosystems. However, we have limited examples of how these processes interact as hosts and their microbes turn over across latitudinal gradients of biodiversity and climate. To bridge this gap, we assembled an ex...

Most instances of detrimental environmental conditions are caused by human behaviour, and the amphibian decline crisis is not an exception. Although some species can be highly popular, amphibians are in general among the least preferred animals by people. This situation represents a source of direct and indirect threats to amphibians. In this chapt...

As the most threatened vertebrate class on earth, amphibians are at the forefront of the biodiversity crisis, with the recognition of global amphibian declines and extinctions dating back several decades now. The current Amphibian Conservation Action Plan is adopting two strategies to address the goal of the amelioration of the amphibian crisis: th...

The bacterial communities of the amphibian skin (i.e., the bacteriome) are critical to the host's innate immune system. However, it is unclear how different drivers can alter this function by modulating the bacteriome's structure. Our aim was to assess the extent to which different host attributes and extrinsic factors influence the structure of th...

Wildlife conservation on private land is an important approach that is increasingly utilized to protect biodiversity and can help contribute to the 30 by 30 target of the Global Biodiversity Framework. In 2018, a Chilean non-profit conservation organization launched a land conservation programme aiming to build long-term partnerships with private l...

Accurate quantification of infection parameters is necessary to ensure effective surveillance, investigation and mitigation of infectious diseases. However, hosts and pathogens are often imperfectly observed and key epidemiological parameters, such as infection prevalence, can be biased if this observational uncertainty is not properly accounted fo...

Actuarial senescence, the increase in adult mortality risk with increasing age, is a widespread phenomenon across the animal kingdom. Although between-species variation in the rate of increase in mortality as organisms age (i.e. ageing rate) is now well documented, the occurrence of variation in ageing rate within a given species remains much more...

Comparative studies of mortality in the wild are necessary to understand the evolution of aging; yet, ectothermic tetrapods are underrepresented in this comparative landscape, despite their suitability for testing evolutionary hypotheses. We present a study of aging rates and longevity across wild tetrapod ectotherms, using data from 107 population...

Amphibian chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), has been recognized as the infectious disease causing the most catastrophic loss of biodiversity known to science, with South America being the most impacted region. We tested whether Bd prevalence is distributed among host taxonomy, ecoregion, conservation status and habita...

Sex-related differences in mortality are widespread in the animal kingdom. Although studies have shown that sex determination systems might drive lifespan evolution, sex chromosome influences on aging rates have not been investigated so far, likely due to an apparent lack of demographic data from clades including both XY (with heterogametic males)...

Emerging infectious diseases in wildlife are increasingly associated with animal mortality and species declines, but their source and genetic characterization often remains elusive. Amphibian chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), has been associated with catastrophic and well-documented amphibian population dec...

Amphibian chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), has caused the greatest known loss of biodiversity due to an infectious disease. We used Bd infection data from quantitative real-time PCR (qPCR) assays of amphibian skin swabs collected across Chile during 2008–2018 to model Bd occurrence with the aim to determin...

Alloparental care, i.e. care directed at non-descendant offspring, has rarely been described in amphibians. Rhinoderma darwinii is an Endangered and endemic frog of the temperate forests of Chile and Argentina. This species has evolved a unique reproductive strategy whereby males brood their tadpoles within their vocal sacs (known as neomelia). Sin...

Entanglement of pinnipeds with plastic debris is an emerging conservation and animal welfare issue worldwide. However, the origins and long-term population level consequences of these entanglements are usually unknown. Plastic entanglement could produce a combination of wounds, asphyxiation, or inability to feed that results in the death of a certa...

Sexual signals in different animals are expected to be dimorphic when both sexes signal, but cases of monomorphism are known to occur, and we lack a clear understanding about the factors that modulate the level of sexual dimorphism in signals. In this study, we evaluated the hypothesis that the lack of dimorphism in sexual signals might evolve in s...

Darwin's frogs Rhinoderma darwinii and Rhinoderma rufum are the only known species of amphibians in which males brood their offspring in their vocal sacs. We propose these frogs as flagship species for the conservation of the Austral temperate forests of Chile and Argentina. This recommendation forms part of the vision of the Binational Conservatio...

Dispersal is a central process in ecology and evolution. It strongly influences the dynamics of spatially structured populations and affects evolutionary processes by shaping patterns of gene flow. For these reasons, dispersal has received considerable attention from ecologists, evolutionary biologists, and conservationists. Although it has been st...

Binational Conservation Strategy fro Darwin's frogs www.estrategiarhinoderma.org

The fungal pathogen Batrachochytrium dendrobatidis (Bd) is the causative agent of chytridiomycosis and has been a key driver in the catastrophic decline of amphibians globally. While many strategies have been proposed to mitigate Bd outbreaks, few have been successful. In recent years, the use of probiotic formulations that protect an amphibian hos...

Amphibian chytridiomycosis, due to infection with the fungus Batrachochytrium dendrobatidis (Bd), has been associated with the alarming decline and extinction crisis of amphibians worldwide. It is essential for conservation management to identify regions with high or low suitability for Bd. We use a species distribution model to estimate the enviro...

Dispersal is a key process in ecology and evolution. Both theoretical and empirical evidence in actively dispersing organisms support the general notion that the use of nearly straight dispersal paths is a highly efficient way to maximize dispersal success in heterogenous landscapes. In homogeneous landscapes, in contrast, the benefits of a straigh...

Dispersal is a central process in ecology and evolution. It strongly influences the dynamics of spatially structured populations, by affecting population growth rate and local colonization-extinction processes. Dispersal can also influence evolutionary processes because it determines rates and patterns of gene flow in spatially structured populatio...

Darwin’s frogs Rhinoderma spp. are the only known mouth-brooding frogs on Earth. The southern Darwin’s frog R. darwinii is found in the temperate forests of southern South America, is listed as endangered, and could be the only extant representative of this genus. Based on stomach content, invertebrate prey availability and stable isotope analysis,...

This PDF file includes: Materials and Methods - Figs. S1, S3, S4, S6, S7, and S9 to S16 - Tables S2 to S5 - Captions for figs. S2, S5, and S8 - Caption for table S1 - Captions for data S1 to S3 - References

Parasitic chytrid fungi have emerged as a signifcant threat to amphibian species worldwide, necessitating the development of techniques to isolate these pathogens into culture for research purposes. However, early methods of isolating chytrids from their hosts relied on killing amphibians. We modifed a pre-existing protocol for isolating chytrids f...

Panzootic chytrid fungus out of Asia Species in the fungal genus Batrachochytrium are responsible for severe declines in the populations of amphibians globally. The sources of these pathogens have been uncertain. O'Hanlon et al. used genomics on a panel of more than 200 isolates to trace the source of the frog pathogen B. dendrobatidis to a hyperdi...

Amphibians are hosts for a wide variety of micro- and macro-parasites. Chigger mites from the Hannemania genus are known to infect a wide variety of amphibian species across the Americas. In Chile, three species (H. pattoni, H. gonzaleacunae and H. ortizi) have been described infecting native anurans; however, neither impacts nor the microscopic le...

Emerging fungal diseases represent a threat to food security, animal and human health worldwide. Amphibian chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), has been associated with catastrophic and well-documented amphibian population declines and extinctions. For the first time, Bd was cultured from native and non-native...

Parasitic chytrid fungi have emerged as a significant threat to amphibian species worldwide, necessitating the development of techniques to isolate these pathogens into sterile culture for research purposes. However, early methods of isolating chytrids from their hosts relied on killing amphibians. We modified a pre-existing protocol for isolating...

Climate change is a major threat to biodiversity; the development of models that reliably predict its effects on species distributions is a priority for conservation biogeography. Two of the main issues for accurate temporal predictions from Species Distribution Models (SDM) are model extrapolation and unrealistic dispersal scenarios. We assessed t...

Anthropogenic climate change is a major threat to biodiversity, and the development of models that reliably predict their effects on species distributions is a priority to conservation biogeography. Common issues to temporal predictability of Species Distribution Models (SDM) are model extrapolation and realistic incorporation of dispersal capaciti...

A link between paternal care and territoriality has been described in several anuran species. The southern Darwin's frog (Rhinoderma darwinii) has developed a highly specialized form of paternal care known as neomelia, in which males ingest developing embryos and transport them in their vocal sacs until metamorphosis is completed. Based on the main...

En conservación biológica existe un incremento en los antecedentes de que las enfermedades infecciosas (EIs) pueden afectar especies silvestres causando mortalidades que pueden aumentar el riesgo de extinción. Es así que para conseguir metas en conservación animal hoy se estima necesario conocer el rol de los patógenos en las poblaciones silvestres...

Darwin's frogs (Rhinoderma darwinii and R. rufum) are two species of mouth brooding frogs from Chile and Argentina that have experienced marked population declines. Rhinoderma rufum has not been found in the wild since 1980. We investigated historical and current evidence of Batrachochytrium dendrobatidis (Bd) infection in Rhinoderma spp. to determ...

Darwin's frogs (Rhinoderma darwinii and R. rufum) are two species of mouth-brooding frogs from Chile and Argentina. Here, we present evidence on the extent of declines, current distribution and conservation status of Rhinoderma spp.; including information on abundance, habitat and threats to extant Darwin's frog populations. All known archived Rhin...

Historical sightings of Rhinoderma rufum . (PDF)

Habitat characteristics of extant Rhinoderma darwinii populations. (PDF)

Examined archived Rhinoderma spp. (PDF)

La colaboración científica ha sido considerada como una de las principales características de la ciencia moderna, hecho reflejado en un sostenido aumento en el número de firmas por artículo desde la segunda mitad del siglo XX. El estudio de estas redes de coautoría puede revelar características interesantes de la comunidad científica. Por este m...

Memorias del taller de conservación de anfibios para organismos públicos

La lipidosis hepática es una enfermedad en la que grandes cantidades de grasas son acumuladas en el hígado. La lipidosis hepática ocurre cuando la tasa de acumulación de triglicéridos en el hepatocito excede la tasa de degradación metabólica o su liberación como lipoproteínas. Muchas especies de aves pueden verse afectadas, pero las aves del orden...