Abstract
AbstractAmphibian chytridiomycosis, due to infection with the fungusBatrachochytrium 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 forBd. We use a species distribution model to estimate the environmental suitability ofBdin the Chilean Winter Rainfall–Valdivian Forest biodiversity hotspot. Fourteen environmental variables were used as predictors in the statistical modeling (Maxent, generalized linear models, random forest) which also included 56 independentBd+ localities. High‐risk areas (i.e., suitability above a defined threshold) were validated through prospective field surveys conducted in 2017. As results from Maxent, which only uses presence data, were the only results retained, refugia (i.e., suitability below a defined threshold) were validated with theBdabsences (N = 12) used in the GLM and RF modeling. Our results showed that (1) suitability forBdincreased with human footprint and with shorter distances to urban centers and water bodies and decreased with elevation; (2) climate was not a major factor shaping the current distribution ofBd; and (3) the model predicted high‐risk and refugia areas fairly well. Surveys of 24 new localities in high‐risk areas confirmed that 23 wereBd+; hence, these areas warrant consideration for long‐termBdsurveillance, population monitoring, and disease mitigation. In addition, five localities with apparentBdabsence were found in the predicted high‐risk areas. Our models showed that refugia can exist near high‐risk areas andBd+ sites. Four localities with apparentBdabsence were located within the refugia predicted by the model. PreventingBdtransmission to such refugia is of paramount importance for persistence ofBd‐susceptible amphibian populations. The identification and validation through prospective field surveys of high‐risk areas and refugia are imperative to develop strategies to prevent further arrival and establishment ofBdand also, by identifying amphibian species or populations of conservation concern in such areas, will help to guide specific actions to reduce the biodiversity loss caused by chytridiomycosis.
Highlights
Emerging infectious diseases (EIDs) are increasingly recognized as a major threat to biodiversity (Daszak et al 2000, Cunningham et al 2017)
This is true for amphibians, where population declines and extinctions at the global scale reported in Australia, Costa Rica, and Chile have been linked to the EID chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd; Lips et al 2006, Schloegel et al 2006, Skerratt et al 2007, Wake and Vredenburg 2008, SotoAzat et al 2013a, b, Valenzuela-Sanchez et al 2017)
The response curves for the predictors with the highest gains showed that environmental suitability for Bd increased with human footprint and shorter distances to urban centers and water bodies
Summary
Emerging infectious diseases (EIDs) are increasingly recognized as a major threat to biodiversity (Daszak et al 2000, Cunningham et al 2017). Given the current scenario of rapid environmental change driven by anthropogenic activity, there is growing interest in understanding the role of global change in the emergence and spread of infectious diseases (Jones et al 2008, O’Hanlon et al 2018) This is true for amphibians, where population declines and extinctions at the global scale reported in Australia, Costa Rica, and Chile have been linked to the EID chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd; Lips et al 2006, Schloegel et al 2006, Skerratt et al 2007, Wake and Vredenburg 2008, SotoAzat et al 2013a, b, Valenzuela-Sanchez et al 2017). Bd refugia may protect susceptible amphibians from the constant pressure of Bd spread, or potentially serve as source or destiny areas for amphibian conservation-based translocations
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