Sandro Piazzini

A tropical fish community in thermal waters of southern Tuscany

In a small stream of southern Tuscany (Fossa Calda), fed by hot springs, we discovered a fish community dominated by tropical species, some of which have never previously been reported in Euro-Mediterranean natural freshwater environments. The aim of our research was to ascertain whether the three most abundant and widespread species (Amatitlania nigrofasciata, Hemichromis sp. and Oreochromis niloticus) have become established. Analysis of size class distribution and growth curves showed that the populations of these species are quite large and made up of juveniles, subadults and adults, as is the case in self-sustaining populations. These fishes were probably released intentionally, since they are widely used in aquariums and aquaculture and their survival in Fossa Calda was possible because of the constant high temperature of thermal waters. Spread to other streams seems unlikely. In fact, at some distance from the hot springs, where water temperatures are lower, populations of the tropical species were small.

Development of Biological Diversity in Farmland Ponds

ABSTRACT To describe the rate of pond diversity development and how the age of ponds affects diversity of plants, amphibians, and aquatic insects, eight recently created artificial ponds (four young ponds created in the year 2003 and four new ponds created in the year 2007) were compared to four reference ponds. For each pond, we recorded the presence of plants and the abundance of amphibians and aquatic insects in plots of 0.25 m2 along two orthogonal transects. Data were analyzed using rarefaction technique, permutation tests for multivariate analysis of variance (PERMANOVA), and rank-abundance diagrams. The new and young ponds showed lower plant and aquatic insect species richness than the reference ponds, and the communities showed gradual changes over time in all three taxa Amphibians, which were absent from new ponds, reached the same species richness as in reference ponds five years after pond creation. PERMANOVA wormed on presence/absence data showed no significant differences in community composition for aquatic insects and amphibians among pond age but showed significant differences among ponds belonging to, the same age classes for all taxa studied.

The response of amphibian communities to fish and habitat features in Mediterranean permanent ponds

Generalized linear models were used to test the effect of fish, using ponds with and without fish and habitat features as covariates, on richness and abundance of amphibian species. Five fish species and six amphibian species were recorded in 60 permanent ponds located in central Italy. The choice of covariates (macrophyte cover and pond surface area) was made after studying the correlations. The richness of amphibian species was not significantly affected by fish presence or macrophyte cover, in line with previous studies, since almost all the fish species were non-predatory. However, abundance of urodeles (newts) was negatively affected by fish and positively affected by macrophyte cover. Although fish may strongly influence the abundance and composition of amphibian communities, the results indicate that the cover of aquatic macrophytes may increase the available habitat for amphibians and therefore their abundance. Anuran species preferred ponds where fish were present, since both groups preferred larger ponds. Concordance between fish and amphibian species composition was not found by the Mantel and Partial Mantel tests. This indicates that the fish assemblages do not predict which amphibian species occur in the pond.

Role of Predators, Habitat Attributes, and Spatial Autocorrelation on the Distribution of Eggs in the Northern Spectacled Salamander (Salamandrina perspicillata)

Abstract We predicted that the probability of egg occurrence of salamander Salamandrina perspicillata depended on stream features and predation by native crayfish Austropotamobius fulcisianus and the introduced trout Salmo trutta. We assessed the presence of S. perspicillata at 54 sites within a natural reserve of southern Tuscany, Italy. Generalized linear models with binomial errors were constructed using egg presence/absence and altitude, stream mean size and slope, electrical conductivity, water pH and temperature, and a predation factor, defined according to the presence/absence of crayfish and trout. Some competing models also included an autocovariate term, which estimated how much the response variable at any one sampling point reflected response values at surrounding points. The resulting models were compared using Akaikes information criterion. Model selection led to a subset of 14 models with ΔAICc < 7 (i.e., models ranging from substantial support to considerably less support), and all but one of these included an effect of predation. Models with the autocovariate term had considerably more support than those without the term. According to multimodel inference, the presence of trout and crayfish reduced the probability of egg occurrence from a mean level of 0.90 (SE limits: 0.98–0.55) to 0.12 (SE limits: 0.34–0.04). The presence of crayfish alone had no detectable effects (SE limits: 0.86–0.39). The results suggest that introduced trout have a detrimental effect on the reproductive output of S. perspicillata and confirm the fundamental importance of distinguishing the roles of endogenous and exogenous forces that act on population distribution.