Continental‐scale determinants of population trends in European amphibians and reptiles

Falaschi, Mattia; Manenti, Raoul; Thuiller, Wilfried; Ficetola, Gentile Francesco

doi:10.1111/gcb.14739

Cited by 48 publications

(35 citation statements)

References 66 publications

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“…The cause of any specific decline can be a complex interaction of cumulative and sometimes synergistic factors. Globally, reptile populations declines are driven by a combination of threats, including habitat loss and degradation, introduced invasive species, environmental pollution, global climate change, unsustainable use and persecution, and disease and parasitism (37)(38)(39). In this framework, the emergence of a widespread and virulent infectious disease could exacerbate existing population declines.…”

Section: Discussionmentioning

confidence: 99%

Revisiting Ophidiomycosis (Snake Fungal Disease) After a Decade of Targeted Research

et al. 2021

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Emerging infectious diseases (EIDs) are typically characterized by novelty (recent detection) and by increasing incidence, distribution, and/or pathogenicity. Ophidiomycosis, also called snake fungal disease, is caused by the fungus Ophidiomyces ophidiicola (formerly “ophiodiicola”). Ophidiomycosis has been characterized as an EID and as a potential threat to populations of Nearctic snakes, sparking over a decade of targeted research. However, the severity of this threat is unclear. We reviewed the available literature to quantify incidence and effects of ophidiomycosis in Nearctic snakes, and to evaluate whether the evidence supports the ongoing characterization of ophidiomycosis as an EID. Data from Canada remain scarce, so we supplemented the literature review with surveys for O. ophidiicola in the Canadian Great Lakes region. Peer-reviewed reports of clinical signs consistent with ophidiomycosis in free-ranging, Nearctic snakes date back to at least 1998, and retrospective molecular testing of samples extend the earliest confirmed record to 1986. Diagnostic criteria varied among publications (n = 33), confounding quantitative comparisons. Ophidiomycosis was diagnosed or suspected in 36/121 captive snakes and was fatal in over half of cases (66.7%). This result may implicate captivity-related stress as a risk factor for mortality from ophidiomycosis, but could also reflect reporting bias (i.e., infections are more likely to be detected in captive snakes, and severe cases are more likely to be reported). In contrast, ophidiomycosis was diagnosed or suspected in 441/2,384 free-ranging snakes, with mortality observed in 43 (9.8 %). Ophidiomycosis was only speculatively linked to population declines, and we found no evidence that the prevalence of the pathogen or disease increased over the past decade of targeted research. Supplemental surveys and molecular (qPCR) testing in Ontario, Canada detected O. ophidiicola on 76 of 657 free-ranging snakes sampled across ~136,000 km2. The pathogen was detected at most sites despite limited and haphazard sampling. No large-scale mortality was observed. Current evidence supports previous suggestions that the pathogen is a widespread, previously unrecognized endemic, rather than a novel pathogen. Ophidiomycosis may not pose an imminent threat to Nearctic snakes, but further research should investigate potential sublethal effects of ophidiomycosis such as altered reproductive success that could impact population growth, and explore whether shifting environmental conditions may alter host susceptibility.

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Section: Discussionmentioning

confidence: 99%

Revisiting Ophidiomycosis (Snake Fungal Disease) After a Decade of Targeted Research

et al. 2021

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“…Amphibians are the group showing the highest rate of decline within vertebrates (Hoffmann et al 2010). Alien species are among the greatest threat to amphibians and are involved in many declines and extinctions both at the population and at the species level (Stuart et al 2004;Bellard et al 2016;Falaschi et al 2019). Freshwater ecosystems are particularly sensitive to the introduction of alien species, especially when the introduced species is a predator of native members of the invaded community (Cox & Lima 2006), and are suffering a growing number of introductions of alien predators all over the world (Strayer 2010).…”

Section: Introductionmentioning

confidence: 99%

Long‐term drivers of persistence and colonization dynamics in spatially structured amphibian populations

Falaschi

Giachello

Parrino

et al. 2021

Conservation Biology

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Many organisms live in networks of local populations connected by dispersing individuals, called spatially structured populations (SSPs), where the long-term persistence of the entire network is determined by the balance between two processes acting at the scale of local populations: extinction and colonization. When multiple threats act on an SSP, a comparison of the different factors determining local extinctions and colonizations is essential to plan sound conservation actions. Here we assessed the drivers of long-term population dynamics of multiple amphibian species at the regional scale. We used dynamic occupancy models within a Bayesian framework to identify the factors determining persistence and colonization of local populations. Since connectivity among patches is fundamental for SSPs dynamics, we considered two measures of connectivity acting on each focal patch: incidence of the focal species and incidence of invasive crayfish. We used meta-analysis to summarize the effect of different drivers at the community level. Persistence and colonization of local populations were jointly determined by factors acting at different scales. Persistence probability was positively related to the area and the permanence of wetlands, while it showed a negative relationship with the occurrence of fish. Colonization probability was highest in semipermanent wetlands and in sites with a high incidence of the focal species in nearby sites, while it showed a negative relationship with the incidence of invasive crayfish in the landscape. By analyzing long-term data on amphibian population dynamics, we found a strong effect of some classic features commonly used in SSP studies, such as patch area and focal species incidence. The presence of an invasive alien species at the landscape-scale emerged as one of the strongest drivers of colonization dynamics, suggesting that studies on SSPs should consider different connectivity measures more frequently, such as the incidence of predators, especially when dealing with biological invasions.

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“…2017, Falaschi et al. 2019). While there are many known causes contributing to declines (e.g., pathogens, overharvesting, habitat loss; Stuart et al.…”

Section: Introductionmentioning

confidence: 98%

Estimation of breeding probability can make monitoring data more revealing: a case study of amphibians

Cruickshank

Bergamini

Schmidt

2021

Ecological Applications

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Monitoring programs serve to detect trends in the distribution and abundance of species. To do so, monitoring programs often use static state variables. Dynamic state variables that describe population dynamics might be more valuable because they allow for a mechanistic understanding of the processes that lead to population trends. We fit multistate occupancy models to data from a country-wide multispecies amphibian occupancy monitoring program and estimated occupancy and breeding probabilities. If breeding probabilities are determinants of occupancy dynamics, then they may serve in monitoring programs as state variables that describe dynamic processes. The results showed that breeding probabilities were low and that a large proportion of the populations had to be considered to be non-breeding populations (i.e., populations where adults are present but no breeding occurs). For some species, the majority of populations were non-breeding populations. We found that non-breeding populations have lower persistence probabilities than populations where breeding occurs. Breeding probabilities may thus explain trends in occupancy but they might also explain other ecological phenomena, such as the success of invasive species, which had high breeding probabilities. Signs of breeding, i.e., the presence of eggs and larvae, were often hard to detect. Importantly, non-breeding populations also had low detection probabilities, perhaps because they had lower abundances. We suggest that monitoring programs should invest more in the detection of life history stages indicative of breeding, and also into the detection of nonbreeding populations. We conclude that breeding probability should be used as a state variable in monitoring programs because it can lead to deeper insights into the processes driving occupancy dynamics.

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Continental‐scale determinants of population trends in European amphibians and reptiles

Cited by 48 publications

References 66 publications

Revisiting Ophidiomycosis (Snake Fungal Disease) After a Decade of Targeted Research

Revisiting Ophidiomycosis (Snake Fungal Disease) After a Decade of Targeted Research

Long‐term drivers of persistence and colonization dynamics in spatially structured amphibian populations

Estimation of breeding probability can make monitoring data more revealing: a case study of amphibians

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