Examinando por Autor "Schmidt, Benedikt R."
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Ítem Assessing habitat quality when forest attributes have opposing effects on abundance and detectability: A case study on Darwin's frogs(Forest Ecology and Management, 2019-01-15) Valenzuela-Sánchez, Andrés; Schmidt, Benedikt R.; Pérez, Catalina; Altamirano, Tania; Toledo, Verónica; Pérez, Ítalo; Teillier, Sebastián; Cunninghami, Andrew A.; Soto-Azat, ClaudioForest 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 effects on species abundance and the detectability of individuals, impairing our ability to detect useful habitat quality surrogates and to provide correct forest management recommendations. Using spatially stratified capture-recapture models (a.k.a. multinomial N-mixture models), we evaluated the effects of stand-level forest attributes on detection probability and local abundance for the endangered Southern Darwin's frog (Rhinoderma darwinii), a forest-specialist and fully terrestrial amphibian endemic to the South American temperate forest. Our results show that an increase of stand basal area and a decrease of daily microclimatic fluctuation (i.e. an increase in structural complexity) were positively associated with the local abundance of R. darwinii. These stand-level forest attributes also explained the among-population variation in detection probability, although the relationships were opposite to those for abundance. Consequently, an analysis of raw frog counts (i.e. not adjusted for imperfect detection) did not reveal all the factors associated with local abundance. Our results provide further support to previous claims that raw counts of individuals should not be used, generally, as a proxy of abundance in species inhabiting forest ecosystems and elsewhere. More importantly, the opposite effect of forest attributes on abundance and detectability observed in our study highlights the need to use methods that quantify species-habitat relationships in a robust way and which take habitat-specific imperfect detection into account.Ítem Cryptic disease-induced mortality may cause host extinction in an apparently stable host-parasite system(Proceedings of the Royal Society, 2017-09) Valenzuela-Sánchez, Andrés; Schmidt, Benedikt R.; Uribe-Rivera, David E.; Costas, Francisco; Cunningham, Andrew A.; Soto-Azat, ClaudioThe 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. Understanding host- parasite dynamics leading to persistence of the system is imperative to adequately inform conservation practice. Here we combine field data, statistical and mathematical modelling to explore the dynamics of the apparently stable Rhinoderma darwinii-Batrachochytrium dendrobatidis (Bd) system. Our results indicate that Bd-induced population extirpation may occur even in the absence of epidemics and where parasite prevalence is relatively low. These empirical findings are consistent with previous theoretical predictions showing that highly pathogenic parasites are able to regulate host populations even at extremely low prevalence, highlighting that disease threats should be investigated as a cause of population declines even in the absence of an overt increase in mortality. © 2017 The Author(s) Published by the Royal Society. All rights reserved.Ítem Interpopulation differences in male reproductive effort drive the population dynamics of a host exposed to an emerging fungal pathogen(John Wiley and Sons Inc, 2022-02) Valenzuela-Sánchez, Andrés; Azat, Claudio; Cunningham, Andrew; Delgado, Soledad; Bacigalupe, Leonardo D.; Beltrand, Jaime; Serrano, José M.; Sentenac, Hugo; Haddow, Natashja; Toledo, Verónica; Schmidt, Benedikt R.; Cayuela, HugoCompensatory 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 survival at early life stages, change in reproductive traits) as well as the level of interpopulation variation in this response are poorly known. We explore potential mechanisms of compensatory recruitment in response to Bd infection by taking advantage of an amphibian system where male reproductive traits are easy to quantify in free-living populations. The Southern Darwin's frog Rhinoderma darwinii is a vocal sac-brooding species that exhibits a high susceptibility to lethal Bd infection. Using a 7-year capture–recapture study at four populations with contrasting Bd infection status (one high prevalence, one low prevalence and two Bd-free populations), we evaluated whether Bd-positive populations exhibited a higher adult recruitment and a higher male reproductive effort than Bd-negative populations. We also estimated population growth rates to explore whether recruitment compensated for the negative impacts of Bd on the survival of adults. In addition, we evaluated a potential demographic signal of compensatory recruitment (i.e. positive relationship between the proportion of juveniles and Bd prevalence) in response to Bd infection using raw count data from 13 R. darwinii populations. The high Bd prevalence population exhibited the highest male reproductive effort and the highest recruitment among the four monitored populations. This led to a growing population during the study period despite high mortality of adult hosts. In contrast, males from the population with low Bd prevalence had a low reproductive effort and this population, which had the lowest adult recruitment, was declining during the study period despite adults having a higher survival in comparison to the high Bd prevalence population. We also found a demographic signal of compensatory recruitment in response to Bd infection in our broader analysis of 13 R. darwinii populations. Our study underlines the importance of interpopulation variation in life-history strategies on the fate of host populations after infectious disease emergence. Our results also suggest that an increase in reproductive effort can be one of the processes underlying compensatory recruitment in populations of Bd-susceptible amphibians. © 2021 British Ecological SocietyÍtem Recent Asian origin of chytrid fungi causing global amphibian declines(American Association for the Advancement of Science, 2018-05) O’Hanlon, Simon J.; Rieux, Adrien; Farrer, Rhys A.; Rosa, Gonçalo M.; Waldman, Bruce; Bataille, Arnaud; Kosch, Tiffany A.; Murray, Kris A.; Brankovics, Balázs; Fumagalli, Matteo; Martin, Michael D.; Wales, Nathan; Alvarado-Rybak, Mario; Bates, Kieran A.; Berger, Lee; Böll, Susanne; Brookes, Lola; Clare, Frances; Courtois, Elodie A.; Cunningham, Andrew A.; Doherty-Bone, Thomas M.; Ghosh, Pria; Gower, David J.; Hintz, William E.; Höglund, Jacob; Jenkinson, Thomas S.; Lin, Chun-Fu; Laurila, Anssi; Loyau, Adeline; Martel, An; Meurling, Sara; Miaud, Claude; Minting, Pete; Pasmans, Frank; Schmeller, Dirk S.; Schmidt, Benedikt R.; Shelton, Jennifer M. G.; Skerratt, Lee F.; Smith, Freya; Soto-Azat, Claudio; Spagnoletti, Matteo; Tessa, Giulia; Toledo, Luís Felipe; Valenzuela-Sánchez, Andrés; Verster, Ruhan; Vörös, Judit; Webb, Rebecca J.; Wierzbicki, Claudia; Wombwell, Emma; Zamudio, Kelly R.; Aanensen, David M.; James, Timothy Y.; Thomas P. Gilbert M.; Weldon, Ché; ;Bosch, Jaime; Balloux, François; Garner, Trenton W. J.; Fisher, Matthew C.Globalized infectious diseases are causing species declines worldwide, but their source often remains elusive. We used whole-genome sequencing to solve the spatiotemporal origins of the most devastating panzootic to date, caused by the fungus Batrachochytrium dendrobatidis, a proximate driver of global amphibian declines. We traced the source of B. dendrobatidis to the Korean peninsula, where one lineage, BdASIA-1, exhibits the genetic hallmarks of an ancestral population that seeded the panzootic. We date the emergence of this pathogen to the early 20th century, coinciding with the global expansion of commercial trade in amphibians, and we show that intercontinental transmission is ongoing. Our findings point to East Asia as a geographic hotspot for B. dendrobatidis biodiversity and the original source of these lineages that now parasitize amphibians worldwide. © 2017 The Authors.