Ficetola G.F.,University of Milan Bicocca |
Scali S.,Natural History Museum of Milan |
Denoel M.,University of Liège |
Vukov T.D.,University of Belgrade |
And 2 more authors.
Global Ecology and Biogeography | Year: 2010
Aim: Ecogeographical variation of body size in vertebrates (e.g. Bergmann's rule) has long been recognized. However, the patterns and causes of intra-specific ecogeographical variation of body size in ectotherms, and in amphibians in particular, are strongly debated. We identified the relationship between bioclimatic variables and body size predicted a priori by alternative hypotheses (heat balance, endurance, seasonality, starvation resistance, water availability, primary productivity, parental investment) proposed to explain ecogeographical patterns of body size in ectotherms, and we evaluated the relative support of these hypotheses in explaining variation in body size of the Italian crested newt, Triturus carnifex. Location: Twenty-three populations covering the whole range of T. carnifex (Austria, Croatia, Italy and Slovenia). Methods: We obtained data on body size (snout-vent length, SVL) of 2639 adult newts from direct measurements and the literature; we obtained high-resolution environmental data for the sampled localities. We used an information-theoretic approach to evaluate the support of the data for the different hypotheses. We also integrated information on population genetics in our models. Results: We observed strong geographical variation of body size. The best Akaike information criterion (AIC) models showed that populations with larger body size are associated with cold climates and secondarily with high primary productivity. Furthermore, sexual dimorphism increases in cold climates, as the increase in body size was stronger for females. When taking into account population genetics, we did not find support for relationships with the other variables. Main conclusion: Our results are consistent with three hypotheses proposed to explain ecogeographical variation in amphibians: heat balance, increased parental investment of females and productivity. Information theory provides the framework for comparing hypotheses rather than looking for patterns. We suggest that evaluating the support for mechanisms can provide better insights than simply assessing whether ecogeographical variation is in agreement with some 'rule'. © 2010 Blackwell Publishing Ltd.
Pezzotta F.,Natural History Museum of Milan
Gems and Gemology | Year: 2010
Attractive yellow to light greenish yellow gem scapolites have been mined from a skarn deposit near the town of Ihosy, in southern Madagascar, since the late 1990s. Chemical analysis indicates that the scapolites have a mostly meionite content, with lesser amounts of marialite and a small percentage of silvialite. These results are agreeable with the RI measurements and IR spectra. Inclusions were identified as diopside, garnet (andradite-grossular), and mica (probably phlogopite), consistent with the minerals accompanying scapolite in Ihosy skarns. The samples' UV fluorescence appears to be distinctive from that of commercially available scapolites from other localities. © 2010 Gemological Institute of America.
Adamo I.,University of Milan |
Diella V.,CNR Institute for the Dynamics of Environmental Processes |
Pezzotta F.,Natural History Museum of Milan
Gems and Gemology | Year: 2012
Since 2002, tsavorite and other grossular varieties have been recovered from a primary deposit at Itrafo, a village in the Andrembesoa area of central Madagascar. Twenty-two samples from this locality were investigated by classical gemological methods, chemical analysis, and UV-Vis-NIR and mid-IR spectroscopy. The garnets' chemical composition was nearly pure grossular (>92 mol.%), with iron and vanadium as the main chromophores. Their iron content and Fe2O3:V2 sub>O3 ratio were higher than those generally found in tsavorite from well-known deposits. Although the Itrafo deposit is relatively large, and new veins could be discovered, future production will be limited by access difficulties and security concerns. © 2012 Gemological Institute of America.
Losapio G.,University of Milan |
Losapio G.,University of Zürich |
Gobbi M.,Section of Invertebrate Zoology and Hydrobiology |
Marano G.,University of Milan |
And 9 more authors.
Arthropod-Plant Interactions | Year: 2016
Primary successions of glacier forelands are unique model systems to investigate community dynamics and assembly processes. However, successional changes of plant and insect communities have been mainly analysed separately. Therefore, changes in plant–insect interactions along successional gradients on glacier forelands remain unknown, despite their relevance to ecosystem functioning. This study assessed how successional changes of the vegetation influenced the composition of the flower-visiting insect assemblages of two plant species, Leucanthemopsis alpina (L.) Heyw. and Saxifraga bryoides L., selected as the only two insect-pollinated species occurring along the whole succession. In addition, we investigated the links between reproductive output of these plants and pollinator abundance through experimental exclusion of pollinators. Plant community structure changed along the succession, affecting the distribution and the abundance of insects via idiosyncratic responses of different insect functional groups. L. alpina interacted with ubiquitously distributed pollinators, while S. bryoides pollinators were positively associated with insect-pollinated plant species density and S. bryoides abundance. With succession proceeding, insect assemblages became more functionally diverse, with the abundance of parasitoids, predators and opportunists positively related to an increase in plant cover and diversity. The reproductive output of both plant species varied among successional stages. Contrary to our expectation, the obligate insect-pollinated L. alpina showed a reproductive output rather independent from pollinator abundance, while the reproductive output of the self-fertile S. bryoides seemed linked to pollinator abundance. Observing ecological interactions and using functional traits, we provided a mechanistic understanding of community assembly processes along a successional gradient. Plant community diversity and cover likely influenced insect community assembly through bottom-up effects. In turn, pollinators regulate plant reproductive output through top-down control. We emphasise that dynamics of alpine plant and insect communities may be structured by biotic interactions and feedback processes, rather than only be influenced by harsh abiotic conditions and stochastic events. © 2016 Springer Science+Business Media Dordrecht