Recently, a number of measures of functional diversity have been proposed for data on species presences and absences. One of the most fashionable methods uses cluster analysis of species computed from a matrix of functional characters. Functional diversity is then summarized as the sum of branch lengths of the dendrogram (FDD). Like other graph-theoretical measures of functional diversity, FDD is an increasing function of species richness. This makes FDD inadequate for comparative studies if we want to quantify a component of functional diversity that is not directly related to differences in species counts. The aim of this paper is thus to develop a graph-theoretical measure of functional diversity that does not depend of species richness. The edges of the minimum spanning tree, calculated from the pair-wise inter-species dissimilarity matrix based on functional traits, are ranked and then a power law relationship is established with the cumulative distances. We empirically demonstrate that the exponent of this relationship is independent of species richness and is therefore a suitable measure of functional diversity.
Authors:S. Ibanez, M. Bison, S. Lavorel, and M. Moretti
Herbivory is a major driver of plant communities. Most herbivores preferentially consume dominant species and slow down plant succession, but it remains unclear in which ways different herbivore species have contrasting effects on plant communities. In this study, we investigated the extent to which closely related insect herbivores with slight differences in their feeding behaviour induce contrasting reactions in plant communities. We studied the impact of herbivory by two Gomphocerinae grasshopper species, Chorthippus scalaris and Euthystira brachyptera, on the outcome of competition between the plant species Dactylis glomerata and Festuca paniculata. Under a controlled choice experiment, C. scalaris preferentially consumed D. glomerata while E. brachyptera preferred F. paniculata, but in an experimental plant community (mesocosm) both species consumed the plant species proportionally to their abundance and the amount of herbivory marks detected on the leaves did not depend on the specific grasshopper species. The herbivory pressure of both grasshopper species significantly reduced the vegetative height and the number of tillers of F. paniculata, with C. scalaris showing a stronger effect. As a consequence, herbivory by E. brachyptera did not significantly affect interspecific plant competition, whereas C. scalaris enhanced the dominance of D. glomerata. Our study shows that closely related herbivores that only slightly differ in their feeding behaviour can induce contrasting effects on interspecific plant competition, and that the dominant species D. glomerata is more tolerant to herbivory than F. paniculata. The specific plant and herbivore traits responsible for contrasting herbivory effects on plant competition remains to be explored.
Authors:F. Bello, J. Lepš, S. Lavorel, and M. Moretti
Measurements of trait community composition are known to be sensitive to the way species abundance is assessed, but not to what extent. This was investigated by considering two of the most commonly used indices of community trait composition, trait averages and functional diversity, in bee communities along a post-fire environmental gradient. The indices were computed using three different species abundance measurements (log and unlog number of individuals and species occurrence only) and 5 traits. For certain traits, the responses of the indices to fire varied according to how species abundance was measured. The measurements that took species abundance into account in the most distinct way (e.g., occurrence vs. unlog data) produced the least similar results for all traits. Species were then grouped into different classes on the basis of their relative abundance (i.e., dominants, subdominants, and rare species). As a result, the measure that attaches the highest importance to the abundance of species (unlog data) related mostly to the dominant species traits, while the measure attaching the lowest (i.e., species occurrence) related more to rare species traits. Species diversity was mostly independent of trait averages and functional diversity, regardless of the measure of species abundance used. We also quantified functional redundancy (i.e., the potential minus the observed functional diversity in each community). When more weight was attached to species abundance, redundancy decreased and tended to be less correlated with species diversity. Overall, the way species abundance is taken into consideration in indices of functional composition offers promising insights into the way community assembly mechanisms respond to environmental changes.
The population dynamics of blowflies (Diptera: Calliphoridae) has been investigated in studies combining different mathematical formalisms, with estimates of demographic parameters and spatial models. However, these applications are limited to laboratory data only. In this study, we investigated the population dynamics of three species of blowflies [Chrysomya albiceps (Wiedemann), Chrysomya megacephala (F.) and Lucilia eximia (Wiedemann)] in a mathematical model that includes parameters estimated in the laboratory and population sizes estimated from field collections, in order to simulate the dynamics of local migration. The model combines experimental estimates of fecundity and survival with abundance data obtained in field collections, to analyze comparatively the population dynamics of the three blowfly species, taking into account the theoretical movement by individuals among municipalities with different urbanization profiles. The ecological patterns of oscillation observed depended on the municipality only for C. albiceps, a species with special demographic characteristics that are probably associated with predatory and cannibalistic behaviors. The bifurcation diagrams showed that intermediate migration rates stabilize populations. Although the proposed model considers only six municipalities in a closed system, the study was able to show different impacts of local migration on the quantitative and qualitative population behaviors, by using different connectivity levels arising from the different distances among areas.
Authors:S. Vannini, R. Pagiotti, M. Acito, S. Levorato, L. Dominici, C. Fatigoni, V. Gianfredi, M. Moretti, and M. Villarini
The alkenylbenzene estragole (systematic name, 1-allyl-4-methoxybenzene) is a natural component of essential oils from various spices and herbs, including fennel, and it is used as a food and beverage flavouring agent. Estragole has been reported to be hepatocarcinogenic at high doses in rodents. However, in a previous in vitro study, we found that estragole did not exhibit cytotoxic effects after 4 hours of exposure, nor did it induce DNA damage or apoptosis in human HepG2 hepatoblastoma cells. As fennel tea is widely used for symptomatic treatment of spasmodic gastrointestinal conditions in infants, we aimed at further assessing its safety in a different experimental setting. We thus searched for possible cytogenetic effects and interference with cell-cycle progression in the same human hepatoblastoma cell line. Estragole did not show any clastogenic/aneugenic activities in the cytokinesis-block micronucleus assay, and no effects on cell-cycle checkpoints were observed.
Authors:M. Forte, A. Bertolo, F. D'Alberti, P. De Felice, D. Desideri, M. Esposito, R. Fresca Fantoni, R. Lorenzelli, A. Luciani, M. Magnoni, F. Marsili, A. Moretti, G. Queirazza, S. Risica, R. Rusconi, S. Sandri, R. Trevisi, and M. T. Valentini Ganzerli
In 2002 the Italian Standardisation Organisation (UNI) - Nuclear Energy Commission (UNICEN) - appointed a working group with
the main task of writing a set of standards on drinking water measurements. To date two standards have been designed, namely,
for total alpha- and beta-activity, and 222Rn. Further procedures are under development for measuring 226Ra and U isotopes, and gamma-emitting radionuclides in water. The paper gives an overview of these standards, both developed
and under study, with special attention to the validation of the methods.