Where Land and Water Meet: Making Amphibian Breeding Sites Attractive for Amphibians

The protection of wetlands is a cornerstone in the conservation of pond-breeding amphibians. Because protected wetlands are rarely natural areas, but are often man-made, at least in Europe, it is important that they are well managed to fulfill their intended function. Appropriate management requires knowledge of the ecology of the species, particularly habitat requirements. Here, we combine species monitoring data and habitat mapping data in an analysis where our goal was to describe the factors that determine the occupancy of amphibian species in federally protected amphibian breeding sites. As expected, every species had its own habitat requirements, often a combination of both a terrestrial and aquatic habitat (i.e., landscape complementation). In most species, occupancy was strongly positively affected with the amount of aquatic habitat, but predicted occupancy probabilities were low because the amount of aquatic habitat was low in most sites. The area or proportion of ruderal vegetation also had positive effects on multiple species, while other types of terrestrial habitat (e.g., meadows) led to low occupancy probabilities. The total area of the protected breeding sites was never included in a final model and connectivity was important only for one species (Triturus cristatus). The latter finding implies that the quality of the landscape between breeding sizes is more important than distance per se, while the former implies that the area of some specific habitats within breeding sites is crucial for high occupancies. Thus, increasing the amount of aquatic habitats and likewise terrestrial habitats within protected areas would make them more likely to achieve their conservation objectives. Our study is an example of how the joint analysis of monitoring data and habitat data (based on mapping in the field) can lead to evidence-based suggestions on how to improve conservation practice

Intensive slurry management and climate change promote nitrogen mining from organic matter-rich montane grassland soils

Aims Consequences of climate change and land use intensification on the nitrogen (N) cycle of organic-matter rich grassland soils in the alpine region remain poorly understood. We aimed to identify fates of fertilizer N and to determine the overall N balance of an organic-matter rich grassland in the European alpine region as influenced by intensified management and warming. Methods We combined 15N cattle slurry labelling with a space for time climate change experiment, which was based on translocation of intact plant-soil mesocosms down an elevational gradient to induce warming of +1 °C and + 3 °C. Mesocosms were subject to either extensive or intensive management. The fate of slurry-N was traced in the plant-soil system. Results Grassland productivity was very high (8.2 t - 19.4 t dm ha$^{-1}$ yr$^{-1}$), recovery of slurry $^{15}$N in mowed plant biomass was, however, low (9.6–14.7%), illustrating low fertilizer N use efficiency and high supply of plant available N via mineralization of soil organic matter (SOM). Higher 15N recovery rates (20.2–31.8%) were found in the soil N pool, dominated by recovery in unextractable N. Total $^{15}$N recovery was approximately half of the applied tracer, indicating substantial loss to the environment. Overall, high N export by harvest (107–360 kg N ha$^{-1}$ yr$^{-1}$) markedly exceeded N inputs, leading to a negative grassland N balance. Conclusions Here provided results suggests a risk of soil N mining in montane grasslands, which increases both under climate change and land use intensification

Populations of a Susceptible Amphibian Species Can Grow despite the Presence of a Pathogenic Chytrid Fungus

Disease can be an important driver of host population dynamics and epizootics can cause severe host population declines. Batrachochytrium dendrobatidis (Bd), the pathogen causing amphibian chytridiomycosis, may occur epizootically or enzootically and can harm amphibian populations in many ways. While effects of Bd epizootics are well documented, the effects of enzootic Bd have rarely been described. We used a state-space model that accounts for observation error to test whether population trends of a species highly susceptible to Bd, the midwife toad Alytes obstetricans, are negatively affected by the enzootic presence of the pathogen. Unexpectedly, Bd had no negative effect on population growth rates from 2002–2008. This suggests that negative effects of disease on individuals do not necessarily translate into negative effects at the population level. Populations of amphibian species that are susceptible to the emerging disease chytridiomycosis can persist despite the enzootic presence of the pathogen under current environmental conditions

Within- and Among-Population Variation in Chytridiomycosis-Induced Mortality in the Toad Alytes obstetricans

Background Chytridiomycosis is a fungal disease linked to local and global extinctions of amphibians. Susceptibility to chytridiomycosis varies greatly between amphibian species, but little is known about between- and within-population variability. However, this kind of variability is the basis for the evolution of tolerance and resistance evolution to disease. Methodology/Principal Findings In a common garden experiment, we measured mortality after metamorphosis of Alytes obstetricans naturally infected with Batrachochytrium dendrobatidis. Mortality rates differed significantly among populations and ranged from 27 to 90%. Within populations, mortality strongly depended on mass at and time through metamorphosis. Conclusions/Significance Although we cannot rule out that the differences observed resulted from differences in skin microbiota, different pathogen strains or environmental effects experienced by the host or the pathogen prior to the start of the experiment, we argue that genetic differences between populations are a likely source of at least part of this variation. To our knowledge, this is the first study showing differences in survival between and within populations under constant laboratory conditions. Assuming that some of this intraspecific variation has a genetic basis, this may suggest that there is the potential for the evolution of resistance or tolerance, which might allow population persistence

Verbreitung, Gefährdung und Schutz der Gelbbauchunke in der Schweiz

Die Gelbbauchunke (Bombina variegata) ist in der Schweiz nördlich der Alpen weit verbreitet. Diese Art besiedelt in der Schweiz die für sie typischen Lebensräume, wobei sie derzeit vorwiegend in Sekundärhabitaten wie Kiesgruben und Steinbrüchen vorkommt und nur noch selten in ihren Primärhabitaten wie feuchten Wäldern und Auen entlang von Fließgewässern zu finden ist. Der Bestandsrückgang der Gelbbauchunke in der Schweiz ist markant: Mehr als 50 % der früher bekannten Populationen sind erloschen, und noch bestehende Populationen sind kleiner als früher. Dementsprechend wird diese gemäß der Roten Liste als „stark gefährdet“ eingestufte Art mit zahlreichen Schutzprojekten gefördert, und die Schutzmaßnahmen werden in diesem Artikel vorgestellt. = The yellow-bellied toad (Bombina variegata) is widely distributed in northern Switzerland. The species uses the habitat types which are well-known for the species. Currently, most populations are found in gravel pits and quarries and few occur in primary habi-tats such as alluvial zones and wet forests. The species declined markedly in Switzerland: more than 50 % of the known populations went locally extinct. Existing populations are nowadays smaller than they used to be in the past. Therefore, the species is classified as “endangered” on the national red list. The yellow-bellied toad is the focal species in many conservation projects. Here, we summarize conservation actions suitable to improve population status

Infection loads of surviving and non-surviving individuals.

<p>Infection load, measured in genomic equivalents from rt-PCR reactions and logarithmically transformed, in individuals from the infected treatments at the end of experiment. The black line represents the median, the box represents the interquartile range containing 50% of the values, and whiskers mark the 1.5 fold interquartile range. Outliers are marked with circles. Grey boxes = survivors, white boxes = non-survivors.</p

Body mass in surviving and non-surviving individuals.

<p>Boxplots showing body mass of infected individuals at the beginning of metamorphosis (Gosner stage 42), at the end of metamorphosis (Gosner stage 46) and at the end of the experiment or death. Grey boxes = survivors, white boxes = non-survivors. The black line represents the median, the box represents the interquartile range containing 50% of the values, and whiskers mark the 1.5 fold interquartile range. Outliers are marked with circles. Grey boxes = survivors, white boxes = non-survivors.</p

Survival curves for treatments and populations.

<p>Cox regression on survival depending on treatment and population. The blue line represents the Itraconazole treatment for all populations. Yellow = infected handled, red = infected unhandled. Continuous line = population BLI, dashed line = population BLZ, dotted line = population SGA.</p