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Amphibian larvae inhabiting temporary ponds often exhibit the capacity to accelerate development and undergo metamorphosis in challenging conditions like desiccation. However, not all species exhibit this ability, the yellow‐bellied toad (Bombina variegata) is one such example. The underlying mechanisms behind the inability to accelerate development under desiccation remain largely unexplored. The hypothalamic–pituitary–interrenal (HPI) axis and corticosterone (CORT), which act synergistically with thyroid hormone, are thought to facilitate metamorphosis in response to desiccation stress. In this study, we aimed to investigate whether modification in the HPI axis, particularly CORT levels, contributes to the absence of adaptive plasticity in B. variegata under desiccation stress. The study design included four treatments: high water level, high water level with exogenous CORT, low water level, and low water level with metyrapone (a CORT synthesis inhibitor). The main objective was to evaluate the effects of these treatments on whole‐body corticosterone levels, life history, morphological traits, and oxidative stress parameters during the prometamorphic and metamorphic climax developmental stages. While low water level had no effect on total corticosterone levels, larval period, body condition index, and metamorphic body shape, it negatively affected metamorph size, mass, and growth rate. Our findings suggest that constant exposure to desiccation stress over generations may have led to modifications in the HPI axis activity in B. variegata, resulting in adaptation to changes in water level, evident through the absence of stress response. Consequently, CORT may not be a relevant stress indicator in desiccation conditions for this species. Research Highlights: The pond drying conditions had no influence on the overall corticosterone levels.Inability of Bombina variegata to accelerate development in pond drying conditions could be explained by the modification of endocrine signaling pathways. [ABSTRACT FROM AUTHOR]

Amphibians are experiencing an ascertained global decline, which causes include the introduction of alien species and the (anthropogenic) hybridization between native and exotic taxa. Detecting introductions and assessing their impact on populations of native species is crucial for amphibian conservation. We used mitochondrial and nuclear markers to reveal introgressive hybridization between the native Bombina pachypus and the exotic B. variegata (probably introduced from Albania) in a population from a protected area of central Italy. Almost all genotyped individuals were genetically admixed, showing a larger proportion of the allochthonous genome. To our knowledge, this study provides the first evidence of successful hybridization between the two species (we found both putative F1 and backcrosses), hence representing a new threat to the conservation of the endangered, Italian-endemic B. pachypus. [ABSTRACT FROM AUTHOR]

In this paper, we examined how the oxidative status (antioxidant system and oxidative damage) of Bombina variegata larvae changed during the metamorphic climax (Gosner stages: 42—beginning, 44—middle and 46—end) and compared the patterns and levels of oxidative stress parameters between individuals developing under constant water availability (control) and those developing under decreasing water availability (desiccation group). Our results revealed that larvae developing under decreasing water availability exhibited increased oxidative damage in the middle and end stages. This was followed by lower levels of glutathione in stages 44 and 46, as well as lower values of catalase, glutathione peroxidase, glutathione S-transferase and sulfhydryl groups in stage 46 (all in relation to control animals). Comparison between stages 42, 44 and 46 within treatments showed that individuals in the last stage demonstrated the highest intensities of lipid oxidative damage in both the control and desiccation groups. As for the parameters of the antioxidant system, control individuals displayed greater variety in response to changes induced by metamorphic climax than individuals exposed to desiccation treatment. The overall decrease in water availability during development led to increased oxidative stress and modifications in the pattern of AOS response to changes induced by metamorphic climax in larvae of B. variegata.

Abstract: Economic activities such as logging and mineral extraction can result in the creation of new anthropogenic habitats that host specific biodiversity, including protected species. However, the legislation in many Western European countries requires the rehabilitation of “damaged” areas following logging and mining operations, which can eliminate these early successional habitats. Conservation managers face a dilemma in these situations, but often lack knowledge about the impacts of environmental rehabilitation on the population dynamics of pioneer species and so are unable to take this into account in their actions. We investigated the demography of a spatially structured population of an endangered amphibian (Bombina variegata) that uses waterbodies created by logging activities as breeding sites. Using capture–recapture (CR) data collected during a 9‐year study period, we examined how the destruction of breeding patches due to environmental rehabilitation affected adult survival and the long‐term population growth rate. For this purpose, we used recently developed capture–recapture multievent models to estimate survival and dispersal rates in the spatially structured population. We then used these estimates to simulate population trajectories and viability depending on differing frequency of breeding patch destruction. The multievent models revealed that dispersal not resulting from patch loss was relatively high and was sex biased. They also highlighted that patch destruction had a negative impact on adult survival. Moreover, simulations showed that the increase in patch destruction frequency had a strong negative influence on the population growth rate, even when the number of patches remained constant over time. This impact was intensified if female fecundity was also affected. Synthesis and applications. Our study quantifies for the first time the detrimental effect of habitat rehabilitation on the population dynamics of an endangered, pioneer species. Our results show that this deleterious impact of patch destruction could be reduced by certain management practices, such as avoiding the systematic rehabilitation of the breeding patches and compensating for patch destruction by creating substitute breeding patches. [ABSTRACT FROM AUTHOR]

Amphibians are considered to be the most threatened group of vertebrates. Among the multiple factors involved in their decline, habitat loss and alteration as a result of human activities is a major threat. At the individual level the effects of habitat alteration are potentially multiple, including a range of morphological and physiological responses. Analysing and understanding these responses is therefore a critical challenge for amphibian conservation. We examined the influence of intensive vehicle traffic (motorbikes and trucks on unpaved pathways) on the body size and condition and on the production of glucocorticoids (i.e. corticosterone) in the yellow-bellied toad Bombina variegata. In particular, we tested the hypothesis that intensive vehicle traffic has a negative influence on body size and body condition, and postulated that it also increases corticosterone production. Using morphometric data and saliva samples collected from four populations in France, we found that intensive vehicle traffic is associated with a decrease in body size and body condition in both males and females. Furthermore, our analysis revealed that corticosterone production was lower in both sexes in populations experiencing intensive vehicle traffic. We suggest that measures should be applied to reduce vehicle traffic intensity on unpaved pathways during toad breeding activity. This is critical for B. variegata, for which man-made ruts and residual puddles could mitigate the loss of natural habitats. [ABSTRACT FROM AUTHOR]

Bombina variegata (L., 1758) is recorded in Turkey for the first time. With the record of the present study, the known easternmost distribution area of the species has been extended from Greece to Turkey. The specimens were collected from Kurtkaya-Enez (Edirne). The morphometric characters and color-pattern features of the specimens were compared with data given in the earlier literature. We observed that the specimens of the Kurtkaya population were similar to the B. v. scabra specimens reported in the literature. [ABSTRACT FROM AUTHOR]

Wildlife disease is an emerging threat to biodiversity. The amphibian chytrid fungus B atrachochytrium dendrobatidis ( Bd), which causes the disease chytridiomycosis, has been documented in over 500 amphibian species globally. Understanding conditions under which amphibians are vulnerable to Bd is important for evaluating species risk and developing surveillance strategies. Here, we investigate the spatial distribution of Bd infection in the ephemeral pond-breeding yellow-bellied toad B ombina variegata, a species of high conservation concern in the European Union. We sampled 550 toads from 60 ponds in a traditional agricultural landscape in Southern Transylvania, Romania. Overall, Bd prevalence was low in B . variegata, but infected toads were widely dispersed through the landscape and were found in a quarter of all sampled ephemeral ponds. At the pond level, increased Bd occurrence was associated with short distances to perennial water sources and high forest cover. These findings suggest that perennial water sources may act as source habitat for Bd, with amphibian movements resulting in Bd spillover into ephemeral ponds. Increased Bd occurrence in ponds surrounded by high levels of forest cover is likely related to cooler and wetter conditions that are more favourable for Bd. Throughout the study landscape, patchy environmental suitability for Bd appears to restrict the pathogen to a subset of B . variegata habitat. Ephemeral ponds in open landscapes, without nearby perennial habitat, likely provide an environmental refuge from Bd, where the risk of infection is low. From a conservation perspective, these findings highlight the importance of maintaining ephemeral ponds in open landscapes, but these are currently threatened by land-use change. [ABSTRACT FROM AUTHOR]

In Western Europe, habitat loss and landscape fragmentation has led to significant population decline in various animal groups, including amphibians. The extinction of the last natural populations of the yellow-bellied toad in Belgium, Luxembourg and several regions of southern and western France suggests a widespread decline. By using site-occupancy models and adding covariates corresponding to the human-influenced features of the landscape, we tried to identify the relative effects of different land-use types on the species' distribution pattern in a man-made environment (the Alsatian Rhine floodplain in France). We recorded presence-absence data in 150 forest sample plots (300 × 300 m) and then modeled species distribution while taking into account detection errors in the field. Land-use was recorded on two spatial scales: within the forest sample plots and in a 1500 m radius buffer area around the forest plots. In the forest plots, toad occurrence was negatively correlated with loss of forest cover to agricultural land. In contrast, occurrence is positively correlated with the density of human-made rutted dirt paths and tracks, which provide semi-natural breeding sites. In the 1500 m radius buffer zones around forest plots, toad occurrence was negatively correlated with the density of urbanization and road networks. These results can be used to plan conservation strategies for amphibians in human-dominated landscapes. [ABSTRACT FROM AUTHOR]

Impending land-use change, including agricultural intensification, is increasingly threatening biodiversity in traditional rural landscapes. To ensure the persistence of species that are vulnerable to land-use change it is necessary to identify and protect high quality habitat before species start to decline. Given that many potentially vulnerable species are still widespread in traditional rural landscapes, it is difficult to identify particularly important locations for such species. Presence-absence data on a given species may have limited application in such cases. As an alternative to presence-absence data, we investigated the influence of environmental variables on the physiological body condition of Bombina variegata (yellow-bellied toad) in a traditional rural landscape in Transylvania, Romania. The species is internationally endangered but remains common throughout our study area. Based on body condition measurements of 550 toads from 60 ponds, we found that toads in forest ponds had significantly better body condition than those in pasture ponds, indicating that forest landscapes provided particularly high quality habitat. We suggest that measures such as body condition-in addition to distribution data-could have considerable application in identifying high quality habitat for other species that are still widespread in traditional landscapes, but have declined in modernised, but otherwise similar landscapes. [ABSTRACT FROM AUTHOR]

The tadpoles of Yellow-bellied toad (Bombina variegata) can be easily recognized from other Italian anuran species, except those of B. pachypus (though the two congeneric species are allopatric). In this paper we report morphometric data on B. variegata tadpoles from a Lombard population living near a torrent at 450 m a.s.l. On a sample of 264 tadpoles (stages 19-44, according to Gosner, 1960) we measured the following five variables: snout-vent length, tail length, maximum tail height, total length and weight. We found a slight allometric relationship between snout-vent length and tail length, while, as expected, the weight is nearly proportional to the cube of linear measures. According to literature data, our results point to highly constant proportions during the development phases up to prometamorphic stages. The ratio between snout-vent length and tail length was about 0.75 during the whole growing phase, while from stage 42 the proportion increases as the resorption of the tail starts. [ABSTRACT FROM AUTHOR]

Amphibians are declining worldwide and many species are threatened for unknown reasons. In fact, information on ecology of several species are not available due to the lack of studies. The Apennine yellow-bellied toad (Bombina pachypus) is an Italian endemic species in progressive decline in many areas, often for unclear reasons. A two-year study of 116 temporary ponds in a grazing area of the Majella National Park (central Italy) from 2001 to 2002 revealed that: (a) Apennine yellow-bellied toads reproduced in small ponds characterized by high desiccation risk; (b) breeding activity occurred for a prolonged period (at least from May to the beginning of August), during which females spawned clutches of very few eggs in several, successive events; (c) the reproductive success was very low especially because of high egg mortality; and (d) the main cause of mortality was the desiccation of ponds. Consequently, the characteristics of breeding areas (i.e., small, ephemeral ponds) are the most important feature influencing the reproduction. The safeguard of temporary ponds is crucial for the conservation of this amphibian and could preserve also the other species using these pools. [ABSTRACT FROM AUTHOR]

Simple Summary: Global warming alters patterns of precipitation and drought, which are important factors in the survival of amphibian populations. Metamorphosis is affected by environmental changes; this is especially true of metamorphic climax, the crucial stage of amphibian development that is accompanied by significant morphological, physiological and behavioral adaptations necessary for the transition to a terrestrial habitat. This study investigated naturally occurring changes in the cellular oxidative status (antioxidant system and oxidative damage) of yellow-bellied toad larvae during this phase, and how exposure to exogenous factors such as desiccation affected them. Our results revealed clear changes in the antioxidant system's (AOS) response and the levels of oxidative damage during metamorphic climax, with the highest response and damage observed at the end stage. Decreasing water levels during larval development altered the components of the AOS and increased oxidative damage, resulting in increased oxidative stress. The knowledge gained from this study could contribute to a better understanding of the oxidative stress that larvae experience during this critical stage of development, and the consequences of global warming—such as water loss—on amphibians. In this paper, we examined how the oxidative status (antioxidant system and oxidative damage) of Bombina variegata larvae changed during the metamorphic climax (Gosner stages: 42—beginning, 44—middle and 46—end) and compared the patterns and levels of oxidative stress parameters between individuals developing under constant water availability (control) and those developing under decreasing water availability (desiccation group). Our results revealed that larvae developing under decreasing water availability exhibited increased oxidative damage in the middle and end stages. This was followed by lower levels of glutathione in stages 44 and 46, as well as lower values of catalase, glutathione peroxidase, glutathione S-transferase and sulfhydryl groups in stage 46 (all in relation to control animals). Comparison between stages 42, 44 and 46 within treatments showed that individuals in the last stage demonstrated the highest intensities of lipid oxidative damage in both the control and desiccation groups. As for the parameters of the antioxidant system, control individuals displayed greater variety in response to changes induced by metamorphic climax than individuals exposed to desiccation treatment. The overall decrease in water availability during development led to increased oxidative stress and modifications in the pattern of AOS response to changes induced by metamorphic climax in larvae of B. variegata. [ABSTRACT FROM AUTHOR]