Recovery of high mountain Alpine lakes after the eradication of introduced brook trout Salvelinus fontinalis using non-chemical methods

Species eradication for ecosystem restoration

Many of the world's ecosystems are under unprecedented stress as human pressures have escalated to be a dominant driver of ecosystem composition and condition. Direct impacts such as agriculture, extraction, and development are impacting vast swathes of land and ocean, while the effects of human-caused climate change are felt even in the most remote parts of marine and terrestrial wildernesses. These impacts are resulting in changes ranging from ecosystem collapse or replacement to novel mixes of species due to temperature-driven range shifts. While reducing human pressures is paramount for the future viability of vulnerable ecosystems, much attention is now also focused on whether degraded areas can be restored. Indeed, the UN has declared 2021-2030 the Decade on Ecosystem Restoration, which aims to "prevent, halt and reverse the degradation of ecosystems on every continent and in every ocean".

The Gut Microbiota of Farmed and Wild Brook Trout (Salvelinus fontinalis): Evaluation of Feed-Related Differences Using 16S rRNA Gene Metabarcoding

The gut microbiota has become a topic of increasing importance in various fields, including aquaculture. Several fish species have been the subject of investigations concerning the intestinal microbiota, which have compared different variables, including the intestinal portions, the environment, and diet. In this study, the microbiota of farmed and wild brook trout (Salvelinus fontinalis) were analyzed, in which the wall and content of the medial portion of the intestine were considered separately. A total of 66 fish (age class 2+) were sampled, of which 46 were wild and 20 were farmed brook trout, in two different years. Microbiota data were obtained using a 16S metabarcoding approach by analyzing the V3-V4 hypervariable regions of the corresponding 16S rRNA. The data showed that the core microbiota of these species consist of Proteobacteria (Alpha- and Gammaproteobacteria), Actinobacteria, Firmicutes (Bacilli and Clostridia), and, only for farmed animals, Fusobacteria. The latter taxon's presence is likely related to the fishmeal-based diet administered to farmed brook trout. Indeed, alpha and beta diversity analysis showed differences between wild and farmed fish. Finally, statistically significant differences in the microbiota composition were observed between the intestinal walls and contents of wild fish, while no differences were detected in reared animals. Our work represents the first study on the intestinal microbiota of brook trout with respect to both farmed and wild specimens. Future studies might focus on the comparison of our data with those pertaining to other fish species and on the study of other portions of the brook trout intestine.

Larval development and poor trophic resource availability: Local adaptations and plasticity in a widespread amphibian species

Theory predicts that, in organisms with complex life cycles, if the earlier-stage limiting factor induces weak later-stage phenotypes, the development of the later-stage trait should evolve to reduce carry-over effects. Local adaptations could thus favour decoupling of later stages. However, decoupling is not always possible. In this study, we used a widespread amphibian, the European fire salamander (Salamandra salamandra), to assess the role of local adaptations to environmental stressful conditions experienced at the larval stage. We exposed 150 larvae from different altitudes to two conditions: rich food and poor food condition. Conditions in early life stages can affect an individual's traits, either as a direct effect or mediated through outcomes in successive life stages. To distinguish between effects of rearing conditions and local adaptation, we searched for a causal model. The causal model detected effects of both food treatment and population origin (altitude) on all life stages. Larvae reared under rich food condition metamorphosed earlier, had higher growth rates and reached smaller size at metamorphosis. Significant differences occurred between larvae of different origin: low-altitude individuals performed poorly under the poor food treatment. Moreover, larvae from higher altitudes were slower with rich food and faster with poor food compared to those from lower altitudes. Our results underline that environmental conditions and local adaptation can interplay in determining the plasticity of larval stages, still adaptations can maximize the growth efficiency of early stages in oligotrophic environments, leading to divergent pathways across populations and environmental conditions.

Survived the Glaciations, Will They Survive the Fish? Allochthonous Ichthyofauna and Alpine Endemic Newts: A Road Map for a Conservation Strategy

The Calabrian Alpine newt (Ichthyosaura alpestris inexpectata) is a glacial relict with small and extremely localised populations in the Catena Costiera (Calabria, Southern Italy) and is considered to be "Endangered" by the Italian IUCN assessment. Climate-induced habitat loss and recent fish introductions in three lakes of the Special Area of Conservation (SAC) Laghi di Fagnano threaten the subspecies' survival in the core of its restricted range. Considering these challenges, understanding the distribution and abundance of this newt is crucial. We surveyed the spatially clustered wetlands in the SAC and neighbouring areas. First, we provide the updated distribution of this subspecies, highlighting fish-invaded and fishless sites historically known to host Calabrian Alpine newt populations and two new breeding sites that have been recently colonised. Then, we provide a rough estimate of the abundance, body size and body condition of breeding adults and habitat characteristics in fish-invaded and fishless ponds. We did not detect Calabrian Alpine newts at two historically known sites now invaded by fish. Our results indicate a reduction in occupied sites and small-size populations. These observations highlight the need for future strategies, such as fish removal, the creation of alternative breeding habitats and captive breeding, to preserve this endemic taxon.

Scientists' warning of threats to mountains

Mountains are an essential component of the global life-support system. They are characterized by a rugged, heterogenous landscape with rapidly changing environmental conditions providing myriad ecological niches over relatively small spatial scales. Although montane species are well adapted to life at extremes, they are highly vulnerable to human derived ecosystem threats. Here we build on the manifesto 'World Scientists' Warning to Humanity', issued by the Alliance of World Scientists, to outline the major threats to mountain ecosystems. We highlight climate change as the greatest threat to mountain ecosystems, which are more impacted than their lowland counterparts. We further discuss the cascade of "knock-on" effects of climate change such as increased UV radiation, altered hydrological cycles, and altered pollution profiles; highlighting the biological and socio-economic consequences. Finally, we present how intensified use of mountains leads to overexploitation and abstraction of water, driving changes in carbon stock, reducing biodiversity, and impacting ecosystem functioning. These perturbations can provide opportunities for invasive species, parasites and pathogens to colonize these fragile habitats, driving further changes and losses of micro- and macro-biodiversity, as well further impacting ecosystem services. Ultimately, imbalances in the normal functioning of mountain ecosystems will lead to changes in vital biological, biochemical, and chemical processes, critically reducing ecosystem health with widespread repercussions for animal and human wellbeing. Developing tools in species/habitat conservation and future restoration is therefore essential if we are to effectively mitigate against the declining health of mountains.

Invasion patterns and niche comparison of the butterfly Cacyreus marshalli among native and non-native range

Alien species introduction is a global phenomenon involving different invasion patterns and is characterized by niche conservatism or shift. We describe the spatial distribution of Cacyreus marshalli Butler, [1898] (Lepidoptera: Lycaenidae) in its native (southern Africa) and invaded (Europe) ranges. C. marshalli is the only alien butterfly in Europe, introduced by the trade of ornamental Pelargonium plants, and might threaten native lycaenids because of the chance of its naturalization on indigenous Geranium spp. In Europe, C. marshalli is widespread in the Mediterranean basin, but absent in northern countries. We investigate invasion patterns and their temporal dynamics in Italy, the most extensively invaded country, identifying three phases and different rates of spread resulting from multiple introductions and human-mediated movements. We also characterize and compare the native and invasive ecological niches of C. marshalli with a multivariate approach based on bioclimatic, ecological and human demographic variables. The little overlap between the native and invaded niches (12.6%) indicates a shift in the realized niche of C. marshalli. While the expansion potential of C. marshalli in Europe remains constrained by the distribution of suitable host plants, our niche comparison analysis suggests the species has already invaded new ecological and climatic spaces. This includes colder areas than would be suggested by its native distribution in Africa.

Using osmotic shock to control invasive aquatic species

Coastal estuaries are especially vulnerable to the arrival and establishment of invasive aquatic species (IAS) as they are often the receiving locations of ship-based introductions. Rapid response tools, such as mechanical or chemical treatments to capture, remove, and contain of IAS, are needed to prevent subsequent spread into adjacent marine and freshwater systems. Abrupt salinity change, created when infrastructure in estuaries situated at the proximity of river mouths is operated, offers a novel, low-cost and environmentally friendly method for potentially controlling IAS. We investigated the use of osmotic shock to control the invasive brackish water clam Rangia cuneata that is quickly spreading through Europe. Clams were exposed in the laboratory to eight salinity concentrations ranging from 0.5 to 32.0‰ and monitored for 60 days. Saline shock, but not freshwater shock, could control R. cuneata. Salinities >26‰ killed 95% R. cuneata in two weeks. All specimens exposed to full strength seawater (32‰) were killed within 30 days. At lower salinities, clams collected from the most freshwater locality (1.2‰) showed lower mortality than clams from the most saline site (3.1‰). Furthermore, even modest increases in salinity during spawning periods of R. cuneata may prevent recruitment. Given the vulnerability of coastal estuaries to introduction of IAS, saline flushing presents a novel and effective management tool for many species.

Reciprocal Role of Salamanders in Aquatic Energy Flow Pathways

Many species of salamanders (newts and salamanders per se) have a pivotal role in energy flow pathways as they include individuals functioning as prey, competitors, and predators. Here, I synthesize historic and contemporary research on the reciprocal ecological role of salamanders as predators and prey in aquatic systems. Salamanders are a keystone in ecosystem functioning through a combination of top–down control, energy transfer, nutrient cycling processes, and carbon retention. The aquatic developmental stages of salamanders are able to feed on a wide variety of invertebrate prey captured close to the bottom as well as on small conspecifics (cannibalism) or other sympatric species, but can also consume terrestrial invertebrates on the water surface. This capacity to consume allochthonous resources (terrestrial invertebrates) highlights the key role of salamanders as couplers of terrestrial and aquatic ecosystems (i.e., aquatic–terrestrial linkages). Salamanders are also an important food resource for other vertebrates such as fish, snakes, and mammals, covering the energy demands of these species at higher trophic levels. This study emphasizes the ecological significance of salamanders in aquatic systems as central players in energy flow pathways, enabling energy mobility among trophic levels (i.e., vertical energy flow) and between freshwater and terrestrial habitats (i.e., lateral energy flow).