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In mountain ecosystems, climate change can cause spatiotemporal shifts, impacting the composition of communities and altering fundamental biotic interactions, such as those involving flower-visiting arthropods. On of the main problems in assessing the effects of climate change on arthropods in these environments is the lack of baseline data. In particular, the arthropod communities on early flowering high-altitude plants are poorly investigated, although the early season is a critical moment for possible mismatches. In this study, we characterised the flower-visiting arthropod community on the early flowering high-altitude Alpine plant, Androsace brevis (Primulaceae). In addition, we tested the effect of abiotic factors (temperature and wind speed) and other variables (time, i.e., hour of the day, and number of flowers per plant) on the occurrence, abundance, and diversity of this community. A. brevis is a vulnerable endemic species growing in the Central Alps above 2000 m asl and flowering for a very short period immediately after snowmelt, thus representing a possible focal plant for arthropods in this particular moment of the season. Diptera and Hymenoptera were the main flower visitors, and three major features of the community emerged: an evident predominance of anthomyiid flies among Diptera, a rare presence of bees, and a relevant share of parasitoid wasps. Temperature and time (hour of the day), but not wind speed and number of flowers per plant, affected the flower visitors’ activity. Our study contributes to (1) defining the composition of high-altitude Alpine flower-visiting arthropod communities in the early season, (2) establishing how these communities are affected by environmental variables, and (3) setting the stage for future evaluation of climate change effects on flower-visiting arthropods in high-altitude environments in the early season.

The biodiversity of our planet is facing a severe crisis. Habitat alteration, climate change, the spread of alien species, and overexploitation are major drivers of biodiversity loss. These global change drivers often act jointly or even synergistically on population declines. To identify priorities for conservation, it is thus essential to compare the relative impact of different threats on biodiversity. Amphibians are the vertebrates showing both the largest proportion of threatened species and the highest rate of decline. Out of the ~6,800 amphibian species assessed by the IUCN, more than 4,000 species are threatened by at least one stressor, and more than 2,000 by at least two stressors. Habitat modification (alteration and/or destruction) and alien species are the two factors threatening the largest number of amphibian species. For this reason, this thesis investigates the role of habitat modification and invasive alien species in determining the temporal dynamics of amphibian populations. The role of these stressors is examined at different spatial scales and jointly with other factors such as microhabitat, landscape, or climatic variables. The first study (Chapter 2) is a continental-scale analysis, which evaluates the combined effects of alien species, habitat availability, habitat changes, and climate change in determining population trends of European amphibian (and some reptile) species over the last 45 years. The results showed that populations declined more often in areas with a high number of alien species and where climate change has caused a loss of climatic suitability. The effect of habitat availability was not relevant when averaged across species; however, when excluding the two commonest species, habitat loss was the main correlate of negative population trends for the remaining species. Furthermore, I observed a strong interaction between habitat availability and the richness of alien species, which indicated that the negative impact of alien species was particularly strong for populations living in landscapes with less suitable habitat Then, the thesis focuses on a specific system: the invasion of the red swamp crayfish Procambarus clarkii in Italy, and its effect on the population dynamics of amphibians. The second study (Chapter 3) presents the updated distribution of the red swamp crayfish in Italy. Thirty years after its first record in Italy in 1989, the red swamp crayfish has invaded 80% of Italian provinces. The invasion is particularly extensive in central and northern Italy, where this invasive crayfish is present in 100% and 96% of provinces, respectively. Given the strong negative effects that the red swamp crayfish can exert on native amphibians, its widespread distribution raises concern about the future status of conservation of the Italian batrachofauna. Chapter 4 analyses site occupancy data of newts in northern Italy, in an area suffering the introduction of the invasive crayfish, in order to investigate the role of microhabitat, landscape change, and invasive species in determining the decline of two newt species through time. Initial occupancy of newts was negatively affected by landscape alteration (i.e. urban and agricultural cover) and by the presence of fish. Both species suffered a strong decline, with a net loss of site occupancy of 25%?36% along the study period. After the crayfish invasion, the main drivers of population dynamics sharply shifted, and occupancy changes were not determined by landscape or microhabitat alterations, as the strongest predictor of local extinctions was the colonization of wetlands by invasive crayfish. The last study (Chapter 5) focuses on the effect of habitat characteristics and invasive crayfish in determining the temporal dynamics of the amphibian community in a large number of wetlands in northern Italy. Since connectivity among wetlands is fundamental for the dynamics of spatially structured populations, we considered two measures of connectivity acting on each focal wetland: incidence of the focal species, and incidence of invasive crayfish. Survival and colonization of local populations were jointly determined by factors acting at different scales. Survival 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 semi-permanent wetlands and in sites with a high incidence of the focal species in nearby sites. Furthermore, the incidence of invasive crayfish emerged as one of the strongest drivers of colonization probability. In this thesis, I showed that invasive alien species are a major driver of the decline of European amphibians. The negative effect of invasive alien species acted differently across species and spatial scales. While the site-level impact was evident only for a subset of species, the landscape-level effect of invasive crayfish was ubiquitous across the whole amphibian community. Habitat modification showed a less evident effect, but invasive alien species and habitat modification can strongly interact: the negative effect of alien species is exacerbated in highly modified landscapes. It is thus essential to directly prevent and manage the spread of alien species, while simultaneously preserving natural landscapes. This can help in mitigating the negative effects of invasives, even when habitat alteration is not the main threatening factor.

Recently described species suffer lack of information that hampers setting up appropriate conservation strategies. The situation is particularly complex with micro-endemic snakes, for which detection and monitoring are particularly challenging. The Walser viper Vipera walser is a recently described snake inhabiting a small area of the SW Italian alps. We combined information on species distribution with repeated monitoring to identify the areas most suitable for the species, and to obtain estimates of species abundance. Species distribution models were used to identify the topographical, climatic, and land-cover features related to the occurrence of vipers. Furthermore, repeated transects and N-mixture models were used to estimate abundance and to identify factors related to the variation of abundance. The available data suggested that the species has a disjunct range, with a Northern range of ~45 km2, and a southern range of ~225 km2. Distribution models suggested that vipers are associated with areas with open vegetation, altitude between 1300 and 2300 m, high precipitation, low forest cover, low slope, and southern aspect. N-mixture models confirmed very low detection probability of these vipers, and suggested that the species has a low abundance, with the highest abundance in south-facing plots. We provide the first quantitative information on habitats and abundance variation for Walser vipers. The broad confidence intervals of abundance estimates exemplify the complexity of providing range-wide measures of abundance for secretive species. Given the narrow range of these vipers, continuous monitoring is required to understand how they respond to ongoing environmental changes in mountainous areas., Acta Herpetologica, Vol. 15 No. 2 (2020): Acta Herpetologica 15(2) 2020