Long-Term Monitoring of Amphibian Populations of a National Park in Northern Spain Reveals Negative Persisting Effects of Ranavirus, but Not Batrachochytrium dendrobatidis

Abstract

Amphibians are the most highly threatened vertebrates, and emerging pathogens are a serious threat to their conservation. Amphibian chytrid fungi and the viruses of the Ranavirus genus are causing disease outbreaks worldwide, including in protected areas such as National Parks. However, we lack information about their effect over amphibian populations in the long-term, and sometimes these mortality episodes are considered as transient events without serious consequences over longer time-spans. Here, we relate the occurrence of both pathogens with the population trends of 24 amphibian populations at 15 sites across a national Park in northern Spain over a 14-year period. Just one out 24 populations presents a positive population trend being free of both pathogens, while seven populations exposed to one or two pathogens experienced strong declines during the study period. The rest of the study populations (16) remain stable, and these tend to be of species that are not susceptible to the pathogen present or are free of pathogens. Our study is consistent with infectious diseases playing an important role in dictating amphibian population trends and emphasizes the need to adopt measures to control these pathogens in nature. We highlight that sites housing species carrying Ranavirus seems to have experienced more severe population-level effects compared to those with the amphibian chytrid fungus, and that ranaviruses could be just as, or more important, other more high-profile amphibian emerging pathogens.

Phylogeographic advances in midwife toads ( Alytes ) support the existence of a novel taxon endemic to the Central Pyrenees

“…The new subspecies is potentially threatened given its narrow distribution range and presumed sensitivity to emerging pathogens ( Ranavirus , chytrid fungus), which are known to decimate Alytes in northern Spain (Bates et al, 2018; Bosch et al, 2021). Global warming could also have a negative long‐term impact, by reducing its range through altitudinal shifts.…”

Relationship between two pathogens in an amphibian community that experienced mass mortalities

“…For example, cumulative or amplified effects caused by the asynchronous emergence of these two lethal pathogens were not found in a study conducted in the Serra da Estrela in Portugal (Rosa et al., 2017). In fact, Rv drove the declines of host assemblages and changed host community composition and structure, even at sites where Bd was not having deleterious impacts (Bosch et al., 2021; Rosa et al., 2013, 2017). Moreover, infection with one pathogen did not increase the probability of co‑infection in two susceptible species across two sites in Picos de Europa National Park, Spain (Bosch et al., 2020).…”

“…Amphibian communities in Iberia are exposed to Bd and Rv, but the number of outbreaks associated with one or the other pathogen has rapidly increased since the late 1980s (Bosch et al., 2001, 2021; Márquez et al., 1995; Price et al., 2014; Rosa et al., 2017; Thumsová et al., 2021, 2022). Although Bd is an introduced and a spreading pathogen in Iberia (O'Hanlon et al., 2018), a more recently described Rv linage (the Common midwife toad virus [CMTV]) may be endemic to the region (Thumsová et al., 2022), originating from the area of the most recent mass mortalities (Flechoso et al., 2019).…”

Effect of natural abiotic soil vibrations, rainfall and wind on anuran calling behavior: a test with captive-bred midwife toads (Alytes obstetricans)

“…The playback experiments were completed between in June and July 2020 in the Amphibian Recovery Center of the Sierra de Guadarrama National Park, where a captive population of midwife toads ( Alytes obstetricans , Alytidae) is established for the reintroduction of the toads in their natural habitats (Martín-Beyer et al 2011 ). This anuran species is widespread across Europe but has suffered substantial declines throughout its range and population size, especially due to chytridiomycosis and ranavirosis (e.g., Bosch et al 2001 , 2021 ). The genus is known for its remarkable reproductive behavior, with males carrying the eggs entwined around their hind legs on land for about a month, from fertilization to hatching.…”