The demography of Atelopus decline: Harlequin frog survival and abundance in central Panama prior to and during a disease outbreak

Abstract

a b s t r a c tHarlequin frogs (Bufonidae: Atelopus) are a species-rich genus of Neotropical toads that have experienced disproportionately severe population declines and extinctions caused by the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd). The genus Atelopus is of high conservation concern, but relatively little is known about the population dynamics and life history of the majority of species. We examined the demography of one population of Atelopus zeteki and two populations of A. varius in central Panama using three to six years of mark-recapture data collected prior to and during an outbreak of Bd. We estimated male survival probabilities prior to the arrival of Bd and sex-specific population sizes for these three populations using state-space Bayesian population models. Prior to the arrival of Bd, monthly apparent survival probabilities were higher for A. varius males than for A. zeteki males, and recaptures among years were low in both species. Abundance of both species varied over time and declined rapidly after the arrival of Bd. Male densities were generally greater than female densities, though female densities were higher or equivalent to males after the arrival of Bd. Estimates of survival and abundance over time may be explained by differences in the use of stream habitat by the two sexes and three populations, both during and between breeding seasons. These estimates provide key baseline population information that can be used to inform reintroductions from captive assurance colonies and studies of extant Atelopus populations as part of conservation and management programs.

Aportes al conocimiento de la ecología de Atelopus balios (Anura: Bufonidae) en el Naranjal, Ecuador

“…En la población estudiada de Atelopus balios la proporción de machos/hembras fue de 8.6:1. Siendo similar a lo reportado en Atelopus varius, donde se registró una proporción de 8.08:1 (14). Pero difieren de lo registrado en Atelopus spumarius donde fue de 4.1:1 (15), en Atelopus zeteki que fue de 2.24:1 (14), en Atelopus cruciger que fue de 2:1 (16), y en contraste para Atelopus laetissimus que fue de 24.5:1 (17).…”

The evolution of stage-specific virulence: Differential selection of parasites in juveniles

“…Recent work has shown that adult virulence in several frog populations has not decreased even after 20 years of Bd presence (Voyles et al ). Already, frog demography has been implicated as an important factor for population persistence in the face of Bd with frog species where adults move away from breeding waters being more resistant to population declines (Lips et al ; McCaffery et al ), and frogs in habitats with multiyear larvae having more severe epidemics because the older stages maintain high levels of infection that then spill over to infect other stages and species (Medina et al ; Hite et al ). The assortativity of mixing clearly has important implications for disease transmission across stages, and our model suggests that it could also have implications for the maintenance of high virulence in different age stages.…”

The evolution of stage-specific virulence: differential selection of parasites in juveniles

“…Recent work has shown that adult virulence in several frog populations has not decreased even after 20 years of Bd presence (Voyles et al 2018). Already, frog demography has been implicated as an important factor for population persistence in the face of Bd with frog species where adults move away from breeding waters being more resistant to population declines (Lips et al 2006;McCaffery et al 2015), and frogs in habitats with multi-year larvae having more severe epidemics because the older stages maintain high levels of infection that then spill over to infect other stages and species (Medina et al 2015;Hite et al 2016). Changes in the assortativity of mixing clearly has important implications for disease transmission across stages, and our model suggests that it could also have implications for the maintenance of high virulence in different age stages.…”