Fiorenza De Bernardi

Influence of landscape elements in riparian buffers on the conservation of semiaquatic amphibians.

Studies on riparian buffers have usually focused on the amount of land needed as habitat for the terrestrial life stages of semiaquatic species. Nevertheless, the landscape surrounding wetlands is also important for other key processes, such as dispersal and the dynamics of metapopulations. Multiple elements that influence these processes should therefore be considered in the delineation of buffers. We analyzed landscape elements (forest cover, density of roads, and hydrographic network) in concentric buffers to evaluate the scale at which they influence stream amphibians in 77 distinct landscapes. To evaluate whether our results could be generalized to other contexts, we determined whether they were consistent across the study areas. Amphibians required buffers of 100-400 m of suitable terrestrial habitat, but interspecific differences in the amount of habitat were large. The presence of amphibians was related to roads and the hydrographic network at larger spatial scales (300-1500 m), which suggests that wider buffers are needed with these elements. This pattern probably arose because these elements influence dispersal and metapopulation persistence, processes that occur at large spatial scales. Furthermore, in some cases, analyses performed on different sets of landscapes provided different results, which suggests caution should be used when conservation recommendations are applied to disparate areas. Establishment of riparian buffers should not be focused only on riparian habitat, but should take a landscape perspective because semiaquatic species use multiple elements for different functions. This approach can be complex because different landscape elements require different spatial extents. Nevertheless, a shift of attention toward the management of different elements at multiple spatial scales is necessary for the long-term persistence of populations.

Trade-off between larval development rate and post-metamorphic traits in the frog Rana latastei

Development rate early in the ontogeny is believed to correlate positively with fitness. Geographic variation in intrinsic development rate suggests the existence of trade-offs between development rate and other fitness related traits. We investigated whether these trade-offs exist between intrinsic larval development rate and post-metamorphic traits in an organism with a complex life cycle. In laboratory, we measured if the tadpoles of the frog Rana latastei with fast intrinsic development rate have a suboptimal post-metamorphic morphology, by comparing froglets from five populations. Then, we evaluated the relationship between age at metamorphosis, hindlimb length and jumping performance for frogs grown in nature in two populations. Under laboratory conditions, froglets with fast intrinsic development had shorter absolute and shorter size-adjusted tibiofibulas. We observed a strong, positive relationship between tibiofibula length and jumping performance. In nature, froglets from the last metamorphosing population had longer absolute and size-adjusted tibiofibulas, and were able to jump further. The cost of fast development could be the shorter legs of early metamorphosing frogs, and their poor jumping performance. Thus, a fast intrinsic development rate may not always be positively related to lifetime fitness, since delayed effects of larval development persist also across life history stages.

Genetic diversity, but not hatching success, is jointly affected by postglacial colonization and isolation in the threatened frog, Rana latastei

Both postglacial colonization and habitat fragmentation can reduce the genetic diversity of populations, which in turn can affect fitness. However, since these processes occur at different spatial and temporal scales, the consequences of either process may differ. To disentangle the relative role of isolation and postglacial colonization in determining genetic diversity and fitness, we studied microsatellite diversity of 295 individuals from 10 populations and measured the hatch rate of 218 clutches from eight populations of a threatened frog, R. latastei. The populations that were affected by fragmentation to a greater extent suffered higher embryo mortality and reduced hatch rate, while no effects of distance from glacial refugium on hatch rate were detected. Altogether, distance from glacial refugium and isolation explained > 90% of variation in genetic diversity. We found that the genetic diversity was lowest in populations both isolated and far from the glacial refugium, and that distance from refugium seems to have the primary role in determining genetic diversity. The relationship between genetic diversity and hatch rate was not significant. However, the proportion of genetic diversity lost through recent isolation had a significant, negative effect on fitness. It is possible that selection at least partially purged the negative effects of the ancestral loss of genetic diversity.

Supplementation or in situ conservation? Evidence of local adaptation in the Italian agile frog Rana latastei and consequences for the management of populations

Relocation of endangered species can be an effective conservation tool if it does not mix populations that represent significant intraspecific variation. The threatened Italian agile frog, Rana latastei, has small populations with low genetic diversity: translocation has been proposed to improve the likelihood of survival of populations. Using a common environment experiment and field surveys, we investigated whether there were differences in larval growth and developmental rate between foothill and lowland R. latastei populations, to evaluate if they are evolutionarily significant units. In nature, the colder climate of the foothills causes delayed metamorphosis. Conversely, in a common environment, larvae from foothill populations show faster growth and development. We did not find a significant egg-size related maternal effect or any differences in size at metamorphosis. We hypothesise that counter-gradient selection promoted fast growing phenotypes in a cold environment, where low temperatures slow down larval development. Foothill populations, despite being only a small geographical distance away from lowland populations, seem to be adapted to a colder climate and represent an evolutionarily significant unit. Different populations should, therefore, be managed independently, avoiding translocation. We suggest that evolutionary divergence between populations should be verified prior to planning relocation programmes, to prevent the risk of genetic homogenisation.

Landscape–stream interactions and habitat conservation for amphibians

Semiaquatic organisms depend on the features of both water bodies and landscapes; the interplay between terrestrial and aquatic systems might influence the semiaquatic communities, determining the scale at which management would be more effective. However, the consequences of such interplay are not frequently quantified, particularly at the community level. We analyzed the distribution of amphibians to evaluate whether the influence of landscape features on freshwater ecosystems can have indirect consequences at both the species and community level. We surveyed 74 streams in northern Italy to obtain data on breeding amphibians, water, and microhabitat features; we also measured features of surrounding landscapes. We used an information-theoretic approach and structural equation models to compare hypotheses on causal relationships between species distribution and variables measured at multiple levels. We also used a constrained redundancy analyses to evaluate causal relationships between multivariate descriptors of habitat features and community composition. Distribution of Salamandra salamandra was related to landscape, hydrological, and water characteristics: salamanders were more frequent in permanent streams with low phosphate concentration within natural landscapes. Water characteristics were dependent on landscape: streams in natural landscapes had less phosphates. Landscape influenced the salamander both directly and indirectly through its influence on phosphates. Community structure was determined by both landscape and water characteristics. Several species were associated with natural landscapes, and with particular water characteristics. Landscape explained a significant proportion of variability of water characteristics; therefore it probably had indirect effects on community. Upland environments play key roles for amphibians, for example, as the habitat of adults, but upland environments also have indirect effects on the aquatic life stages, mediated through their influence on water characteristics. Synergistic effects can magnify the negative consequences of landscape alteration on amphibians; landscape management can be particularly effective, as it can also improve wetland features.

Environmental features influencing Carabid beetle (Coleoptera) assemblages along a recently deglaciated area in the Alpine region

Abstract 1. The spatio‐temporal approach was used to evaluate the environmental features influencing carabid beetle assemblages along a chronosequence of an Italian Alpine glacier foreland. The influence of environmental variables on species richness, morphology (wing and body length), and distribution along the chronosequence was tested.

Epigean Arthropod Succession along a 154-year Glacier Foreland Chronosequence in the Forni Valley (Central Italian Alps)

Abstract The 154-year (1850–2004) chronosequence of the Forni Glacier foreland has been studied by sampling ant, centipede, ground beetle, and spider species assemblages. Species numbers increase with terrain age along the chronosequence from 2 to 26 on the oldest soils. Thirty-nine species were collected; species richness and diversity (Shannons Index) of communities are correlated to the year of soil deglaciation. Shannon Index values increase with sites deglaciated between 1 and 61 years ago; sites deglaciated between 61 and 78 years ago produce similar values, and those deglaciated 78 to 154 years ago show a further increase in diversity. Ground beetles and spiders are found at all sites, while ants and centipedes were associated with mature forest soils. On the glacier surface, pioneer species such as the wolf-spider Pardosa saturatior and the ground beetle Oreonebria castanea permanently inhabit the supraglacial detritus surviving on trophic resources. Wingless ground beetle species are associated with mature soils, especially those with high hydric stability. Open land species typical of primary succession are found in the pioneer and intermediate stages, while community assemblages found on older terrain are linked to forest vegetation structure and dynamics.

Water, stream morphology and landscape: complex habitat determinants for the fire salamander Salamandra salamandra

Understanding the relationship between environmental features and species distribution is a key step for successful habitat conservation. In semiaquatic amphibians, the features of both breeding sites and the surrounding upland habitat can play important roles. We evaluated the relative role of (1) stream morphology, (2) biotic features of water, and (3) composition of landscape surrounding wetlands, for the distribution of the fire salamander, Salamandra salamandra. We determined the presence of larvae in 132 localities, and we used an information-theoretic approach to build species distribution models. We then used variance partitioning to evaluate the relative importance of environmental variables. A model including both stream and landscape features explained a large proportion of variation. Larvae were associated to heterogeneous and shallow streams, with scarce periphyton, rich macrobenthos communities characteristic of oligotrophic water, and surrounded by woodlands. Variance partitioning showed that stream morphology was the parameter with the largest independent effect, but most of variation was explained by the combined effect of multiple variables, suggesting a strong interplay among biotic and abiotic features in determining species distribution. The complementation between multiple elements, such as wetlands and landscape features, can be the key of a correct understanding of distribution of semi-aquatic amphibians.

Serotonin localization in Phallusia mammillata larvae and effects of 5‐HT antagonists during larval development

The neurotransmitter 5‐hydroxytryptamine (5‐HT, serotonin) plays an important role in a wide range of non‐neural processes. Using immunofluorescence with an antiserotonin antibody, 5‐HT was localized in the brain and in some neurons of the larval tail of Phallusia mammillata. To test the effect of 5‐HT on development, we treated embryos with two different 5‐HT receptor subtype antagonists. Treatment at the gastrula stage with 10 μM ondansetron, an antagonist of the 5‐HT3 receptor, induced anterior truncation and a short tail. At 10 μM, ritanserin, a 5‐HT2B receptor antagonist, induced larval phenotypes characterized by a roundish trunk region with flat papillae. The juveniles developed from these larvae had an abnormal cardiocirculatory system: their heart contractions were ineffective and their blood cells accumulated in the heart cavity. We conclude that an appropriate level of 5‐HT is necessary for correct development and morphogenesis. Moreover, a different key role for multiple receptors in modulating the morphogenetic effects of 5‐HT is suggested.

Arthropod colonisation of a debris-covered glacier

The largest debris-covered glacier in the Alps (Miage Glacier, western Italian Alps) has been studied to explore the effects of debris-cover extent and depth on the spatial distribution of ground-dwelling arthropods. A multitaxa approach has been used to compare taxa richness and distribution to the functional role (dietary habits) of each taxon along the glacier tongue. Spiders and ground beetles have been studied in detail. Taxa richness declines with distance from the wooded sites (in front of the glacier tongue) to those above the glacier tongue. At each of the supraglacial sites, spiders, ground beetles, aphids, springtails and flies were found. A change in the dominance of the different functional roles was observed along the tongue. Wooded sites are characterised by predatory (e.g. spiders, beetles), detrivore (e.g. springtails and certain flies), phytophagous (e.g. aphids, certain beetles) and parasitoid (e.g. certain wasps) assemblages, whereas at the debris-covered sites, aphids, flies and springtails are likely to be prey for spiders and beetles. The species richness of the predominant predators (spiders and beetles) shows a positive relationship with vegetation cover and debris thickness. Two mutually exclusive spider and ground beetle assemblages were found; one within the debris cover and one within the wooded sites. In our opinion, debris-covered glaciers are acting as a refuge area for the cryophil stenotherm species living at higher altitudes which descend the glacial tongue to lower elevations. A similar hypothesis supports the biogeographical interpretation of the distribution of many boreo-alpine relict species in the Alps. We discuss our results in the light of possible future scenarios which suggest an increase in debris cover with global warming.