Biogeographical patterns in the diet of the wildcat, Felis silvestris Schreber, in Eurasia: factors affecting the trophic diversity

Aim To analyse the biogeographical patterns in the feeding habits and trophic diversity of prey of the wildcat, Felis silvestris Schreber. Location The Eurasian distribution range from the Caucasian mountains to the Iberian Peninsula and Scotland. Methods We reviewed 15 studies to collate data on feeding behaviour across the current wildcat distribution range. We considered nine prey groups and recorded the latitude, whether the location was within a Mediterranean bioclimate area, and rabbit presence. Prey groups were reduced into four PCA factors. Regression analyses were performed to examine the relationships of latitude with PCA factors and trophic diversity. anova was used to test if trophic diversity was higher at locations with Mediterranean climates. We also analysed the relationship between small rodent consumption and both Mediterranean climates and rabbit presence using anova . Finally, we confirmed the relationship between the frequency of Murinae and Microtinae in the diets and the presence of rabbits and with respect to Mediterranean climates controlling for latitude (mancova ). Results Diet diversity was greatest in Mediterranean climates. Trophic diversity decreased when rodents formed the bulk of the diet, but increased with the inclusion of alternative prey such as rabbits and invertebrates. Small rodent consumption was also negatively related to rabbit consumption or presence. The inclusion of Murinae and Microtinae in the diet varied with latitude, with higher ingestion of the former in the southern locations and of the latter in northern areas. Main conclusions The trophic diversity of the wildcat diet was associated with Mediterranean climatic conditions, being broader at more southern latitudes. At the continental scale, the wildcat cannot be considered a rodent specialist because rabbits were preferred when they were present. Thus, we consider the wildcat to be a facultative specialist. In addition, our results indicate that general trophic patterns in the diet of a species may not be accurately determined if the availability of alternative prey is not taken into account.     

The deleterious effects of salinity stress on leafminers and their freshwater host

Abstract.  1. Salinity is an important cause of abiotic stress in wetland communities yet little is known about its consequences for freshwater plants and their insect herbivores. The goal of this study was to test the effect of salinity on a leafmining insect, Cerodontha iridiphora , and its herbaceous host plant, Iris hexagona .
2. Leafminer performance was evaluated on irises grown in control and saline treatments, and the effects of salinity and herbivory on leaf quality and mortality was measured.
3. Leafminer density and size were significantly lower on irises grown in saline water compared with freshwater.
4. Both salinity and herbivory accelerated leaf senescence and mortality, and their combined effects increased tissue loss by an order of magnitude compared with controls.
5. Leafminers acted as nutrient sinks. The undamaged regions of mined leaves contained 40% less nitrogen than unmined leaves, providing a mechanism for the premature leaf mortality.
6. Salinity was detrimental to the performance and survival of both the iris leafminer and its host plant. We propose that glycophytic host plants and their insect herbivores will suffer more than halophytic communities from environmental salinity because they lack the adaptive mechanisms to tolerate this potent physiological stress.     

Imposex in Hexaplex trunculus at Some Sites on the North Mediterranean Coast as a Base-Line for Future Evaluation of the Effectiveness of the Total Ban on Organotin based Antifouling Paints

Imposex – the superimposition of male sexual organs (penis and vas deferens) onto female Neogastropods such as Hexaplex trunculus (Linné, 1758) – is used world-wide as a biomarker of ecological impact of organotin based antifouling biocides (TBT and TPhT). To limit the impact of organotin pollution, since January 1, 2003, the International Maritime Organization (IMO) has enacted a global ban on the use of organotin compounds in antifouling systems. It is important to record imposex levels and organotin contamination before the implementation of the ban, in order to assess the current situation and be able, in the future, to verify the effects of the International Protocol. In this paper, recent imposex data measured in populations of Hexaplex trunculus from three different Mediterranean regions are compared: the Ligurian Sea (Italy), the Lagoon of Venice (Italy) and the western coast of Istria (Croatia). In the two former locations, a partial ban on TBT has been in force for vessels less than 25 m since 1982, while in the latter region no restrictions on organotin antifouling paints have been applied yet. Gastropod samples collected from the Venice lagoon were analysed with an acid extraction followed by Grignard derivatisation, clean up and GC-MS determination, in order to relate the levels of TBT, TPhT and their metabolites with the imposex degree detected. Biological data show that the levels of imposex were very high (VDS from 4.3 to 5) in all the sampling sites considered, particularly in the Croatian coast stations. The concentrations of organotin compounds – butyltins and phenyltins – measured in the samples from the lagoon of Venice were found to partition differently in the visceral coil and in the rest of the soft body of the analysed organisms.     

Benthic communities on a sandy Ligurian beach (NW Mediterranean)

The different components of the benthic community of a sandy microtidal beach (Arenzano) in Liguria (NW Mediterranean) were investigated during late spring (May) 2002 and 2003. Sampling was carried out in two transects, chosen in order to represent the characteristics of the entire beach and their eventual spatial variations. Each transect included two stations: one placed in the swash zone (SW) and one in the surf zone (SF). Although no significant differences were found in the sediment texture over the 2 years (t-tests p > 0.1 for all the granulometric fractions), notwithstanding an increase in the mean grain size (from 0.8 to 1.1 mm) between the sampling periods, 2002 was characterised by a higher quantity of organic matter (on average 14.4 vs. 3.6 gC m⁻² for the sum of proteins, carbohydrates and lipids) and higher bacterial biomass (on average 1.9 vs. 0.9 gC m⁻²). The metazoan assemblages (meiofauna and macrofauna) were also richer (density = 2.9 × 10⁵ vs. 1.0 × 10⁵ ind. m⁻², biomass = 0.09 vs. 0.03 gC m⁻² for meiofauna; density = 1988 vs. 739 ind. m⁻², biomass = 0.14 vs. 0.03 gC m⁻² for macrofauna) in 2002. A significant quantitative reduction (t-test for proteins, carbohydrates and lipids, at least p = 0.004) in the food supply in 2003 affected the abundance of the metazoans, as confirmed by a multivariate analysis that clearly differentiated the 2 years, and seemed to inhibit their relationships within the benthic food web. The bacterial biomass was always dominant, even under the least favourable trophic conditions, due to the ability of bacteria to adapt to a very harsh environment. Our results suggest that the food supply played an important role in the benthic community structures of the beach during late spring, bacteria being the key organisms within the benthic system. The communities seemed to be bottom-up controlled, while predation seemed to be irrelevant.     

Fish Farming Effects on Chemical and Microbial Variables of the Water Column: A Spatio-temporal Study Along the Mediterranean Sea

The effects of fish farming on chemical and biological variables of the water column were investigated in three coastal locations along the Mediterranean (Spain, Italy and Greece). Analyses of nutrients, chlorophyll a, particulate organic carbon and nitrogen (POC and PON), heterotrophic bacteria and cyanobacteria (Synechococcus) were carried out on integrated samples (0–30 m depth) taken at various distances from fish farms and the respective reference sites. At one of these sites, water samples were collected by means of Niskin bottles at 09:00, 13:00 and 16:00 h and at three different depths (0 m, 10 m and bottom). Integrated sampling showed no significant changes with distance in any of the variables measured, whereas all variables except PON showed significant changes between the three locations studied. However, changes were found in samples taken by Niskin bottles, with increased concentrations of NH₄⁺, POC, PON and decreased cyanobacteria densities at the surface layer in the immediate vicinity of the cages. Samples taken at the cages in the afternoon showed increased PO₄³⁻ concentrations in comparison to those taken in the morning. Dilution and grazing are probably both responsible for the lack of detectable signs of eutrophication.     

Breeding system and spatial variation in the pollination biology of the heterocarpic Thymelaea velutina (Thymelaeaceae)

Thymelaea velutina (Thymelaeaceae) is a unique dioecious and heterocarpic shrub, each female producing both dry and fleshy fruits. It is endemic to the Balearic Islands (western Mediterranean) and has suffered an important regression in recent decades, especially due to habitat loss. It lives in coastal areas, mainly in dunes, but a few populations occur up to 1300 m in the mountains of Mallorca. In the present study, we examined its breeding system and pollen vectors, determined whether seed production is pollen-limited, and quantified the relative importance of different insect visitors at coastal and mountain sites. Selective exclusions showed no differences between populations in the relative importance of insects and wind as pollen vectors. Pollen was limiting at both populations, though not consistently in time. Flowers of T. velutina were visited mostly by generalist insects, and species composition and abundance of flower visitors varied both in space and time. The flowering period is about a month later in the mountain than in the dune, and this results in a higher frequency of insect visits to plants in the mountain due to the higher insect abundance; insects were also more diverse in the mountain, although they visited a proportionally lower number of flowers than in the dune. Despite this spatio-temporal variation in the frequency of insect visits and in the importance of a particular insect group, the ambophilous system in this species (previously described as anemophilous) ensures a relatively high fruit set at the two different sites.     

Characterization of the Y-Chromosome Sardinian–Corsican Haplotype

The Y chromosome of 523 Italian male subjects was examined for the 49a,f TaqI haplotype XII and for two microsatellites, YCAIIa and YCAIIb. Results were then compared to other populations living in the western Mediterranean basin whom we had previously studied: 419 French (including 328 Corsicans), 46 Italians from Milan, and 73 Tunisians. Haplotype XII is present in 127 out of the 1061 examined samples (11.9%), and most of the haplotype XII subjects are of the compound haplotype YCAIIa-21 and YCAIIb-11. Two peaks of haplotype XII frequencies occur in the north of Sardinia (35%) and in the central area of Corsica (17.4%).     

Population dynamics of zooxanthellae during a bacterial bleaching event

Each summer 80–90% of the colonies of Oculina patagonica undergo bleaching off the Mediterranean coast of Israel. To investigate fluctuations through a yearly bleaching cycle, monthly measurements of zooxanthella density, mitotic index and chlorophyll-a concentration were conducted. Results showed (1) a significant negative correlation between sea surface temperature (SST) and zooxanthella density; (2) both significantly lower zooxanthella mitotic index and higher chlorophyll-a per zooxanthella content during the bleaching season compared with the non-bleaching period; (3) prior to bleaching, a lag between the peak of zooxanthella density and chlorophyll-a concentration followed by a similar lag during recovery. Zooxanthella density declined significantly between March and May while chlorophyll-a concentration peaked in April, and then declined. Zooxanthella density increased significantly in November while chlorophyll-a concentration increased significantly in January. We conclude that during bacterial bleaching events, zooxanthellae are severely damaged. However, by the time of the following bleaching event the coral tissues regain their “normal” (pre-bleaching) zooxanthella population density.     

Method to classify xylem cell types using cross sectionsof 1-year-old branches in Mediterranean woody species

Measurements of anatomical parameters of wood are of great interest both for eco-physiological purposes and for technological applications. The aim of this paper is to describe a new method for classifying and measuring cell lumen of xylem, analysing cross sections under the light microscope. The proposed method is based on the application of digital image analysis on images of the cross sections of xylem in combination with graphical and statistical methods. The methodology was tested on 1-year-old branches of several woody species, both trees and shrubs, occurring in a Mediterranean natural ecosystem in southern Italy. The development of the procedure was based on statistical comparison between data collected according to four procedures: (a) manual identification and measurement of lumen diameter of conduits on longitudinal sections; (b) manual identification and measurement of lumen diameter of conduits on cross sections; (c) manual identification and measurement of lumen area of conduits on cross sections; and (d) automatic measurement of lumen area of conduits on cross sections. The influence of image resolution and that of the position of the selected area on cell classification and measurements were ascertained. The proposed method was proved to be specific to woody structures and allowed the construction of a model-graph that is species-specific. Interpretation of the model-graphs allows classification and hence measurement of identified cells.