Multi-scale study of bird species distribution and of their response to vegetation change: a Mediterranean example

Land use changes operate at different scales. They trigger a cascade of effects that simultaneously modify the composition or structure of the landscape and of the local vegetation. Mobil animals, and birds in particular, can respond quickly to such multi-scalar changes. We took advantage of a long term study on the response of songbirds to land-use changes on four Mediterranean islands in Corsica and Sardinia to explore the benefits of a multi-scale analysis of the relationships between songbird distribution, vegetation structure and landscape dynamics. Field data and aerial photographs were used to describe the vegetation at three different scales. Birds were censused by point counts. We used statistical variance decomposition to study how bird distribution and vegetation at various scales were linked. We analysed multi-scale vegetation changes (floristic composition, plot vegetation type, and landscape structure) and their consequences on bird distribution with multivariate and non-parametrical tests. The distribution of most species was linked to at least two spatial scales. The weight of a given scale was consistent with life-history traits for species whose biology was well-known. In the examples studied, vegetation composition, vegetation type and landscape changes that resulted from land abandonment negatively affected birds depending on open or heterogeneous areas. Our results emphasize that multi-scale analyses can greatly enhance our understanding of bird distribution and of their changes. Management of these populations should take into account measures at various spatial scales depending on the sensitivity of the species.     

Response of snails and slugs to fragmentation of lowland forests in NW Germany

Habitat fragmentation is a major cause for species loss, but its effect on invertebrates with low active dispersal power, like terrestrial gastropods, has rarely been studied. Such species can not cross a hostile habitat matrix, for which the predictions of island theory, such as positive relations between species richness and patch size, should apply. In order to test this prediction, we studied gastropod species diversity by assessing gastropod assemblage characteristics from 35 sites in 19 fragments of deciduous old-growth forests in the Lower Rhine Embayment, Germany. Assemblages differed between larger (≥700 ha) and smaller forests (<400 ha), those of large forests held a higher percentage of forest species. Although α-diversity was similar between the two forest size classes, small forests often comprised matrix species, resulting in a higher β-diversity. Edge effects on the species richness of matrix species were noticeable up to 250 m into the forest. Hierarchical partitioning revealed that distance to disturbances (external edge, internal edges like roads) explained most assemblage variables, whereas forest size and woodland cover within a 1 km radius from the sites explained only a few assemblage variables. Densities of two forest-associated species, Discus rotundatus and Arion fuscus, decreased with forest size. Yet, forest size was positively correlated with richness of typical forest species and densities of Limax cinereoniger. The latter species seems to need forests of >1,000 ha, i.e., well above the size of most fragments. In conclusion, the prediction is valid only for forest species. The response to fragmentation is species specific and seems to depend on habitat specialization and macroclimatic conditions. Jean-Pierre Maelfait: Deceased.     

The role of models for multicriteria evaluation and multiobjective design of cropping systems for managing weeds

Weeds are both harmful for crop production and important for biodiversity, while herbicides can pollute the environment. We thus need new cropping systems optimising all cultural techniques, reconciling agricultural production, herbicide reduction and biodiversity conservation. Here, we show how to (i) develop models quantifying the effects of cropping systems on weed dynamics, (ii) integrate interactions between weeds and other organisms, (iii) predict the impact on production and biodiversity and (iv) use the model for multicriteria evaluation and multiobjective design of cropping systems. Among the existing weed dynamics models, we chose the one closest to our requirements to illustrate these different steps, that is, FlorSys which predicts multispecific weed dynamics as a function of cultural techniques and pedoclimate. We have illustrated the development of interaction submodels with the example of a crop pathogen whose propagation is increased when infecting grass weeds. To evaluate the weed flora impact, predicted weed densities were translated into indicators of harmfulness (crop yield loss, technical harvest problems, harvest pollution, field infestation, crop disease increase) and biodiversity (weed species richness and equitability, trophic resources for birds, insects and pollinators). Simulations were run over several years and with different weather scenarios (i) to optimise cultural techniques to control harmful weeds, (ii) to analyse the impact of changing agricultural practices (e.g. simplified tillage and rotations, no‐till, temporary crops) on weed density, species and trait composition and (iii) to evaluate cropping systems for their ability to reconcile agricultural production and biodiversity, thus identifying levers for designing sustainable cropping systems.     

Tracking fungi in soil with monoclonal antibodies

Species of the genus Trichoderma are ubiquitous soil-borne fungi that exhibit antagonism towards a number of economically important plant-pathogenic fungi and oomycetes. This review discusses recent developments in the use of monoclonal antibodies to detect these fungi in their natural soil environments and to quantify their population dynamics during antagonistic interactions with saprotrophic competitors in soil-based systems. Immunological approaches to detection and quantification are examined in relation to conventional plate enrichment techniques and to nucleic acid-based procedures. An example of recent research using a mAb-based assay to quantify the effects of saprotrophic competition on the growth of Trichoderma isolates in mixed species, soil-based, microcosms is presented. Future technological developments in immunoassays for tracking Trichoderma populations in soil are discussed and results presented showing the accurate detection and visualization of a plant growth-promoting isolate of T. hamatum in the rhizosphere of lettuce using mAb-based immunodiagnostic assays.     

Field detection of resistance to isometamidium chloride and diminazene aceturate in Trypanosoma vivax from the region of the Boucle du Mouhoun in Burkina Faso

A longitudinal study assessed the chemoresistance to isometamidium chloride (ISM) and diminazene aceturate (DA) in the region of the Boucle du Mouhoun in Burkina Faso. A preliminary cross-sectional survey allowed the identification of the 10 villages with the highest parasitological prevalences (from 2.1% to 16.1%). In each of these 10 villages, two herds of approximately 50 bovines were selected, one being treated with ISM (1mg/kg b.w.) and the other remaining untreated as control group. All animals (treated and untreated herds) becoming infected were treated with DA (3.5mg/kg b.w.). In total, 978 head of cattle were followed up. Fortnightly controls of the parasitaemia and PCV were carried out during 8 weeks. The main trypanosome species was Trypanosoma vivax (83.6%) followed by Trypanosoma congolense (16.4%). In two villages, less than 25% of the control untreated cattle became positive indicating no need to use prophylactic treatment. These two villages were not further studied. Resistance to ISM was observed in 5 of the remaining 8 villages (Débé, Bendougou, Kangotenga, Mou and Laro) where the relative risk (control/treated hazard ratios) of becoming infected was lower than 2 i.e. between 0.89 (95% CI: 0.43-2.74) and 1.75 (95% CI: 0.57-5.37). In contrast, this study did not show evidence of resistance to DA in the surveyed villages with only 8.6% (n=93) of the cattle relapsing after treatment. Our results suggest that because of the low prevalence of multiple resistances in the area a meticulous use of the sanative pair system would constitute the best option to delay as much as possible the spread of chemoresistance till complete eradication of the disease by vector control operations.     

Effect of Cooling Rate to 5°C,Straw Size and Farm on Fertilizing Ability of Cryopreserved Rabbit Sperm

High fertility and prolificacy in rabbits are currently only achieved using fresh sperm. This study was conducted to determine if the cooling rate to 5°C, the straw size and the farm where artificial inseminations are performed have an impact on the fertilizing ability of rabbit sperm cryopreserved with an extender containing dimethyl sulphoxide (DMSO; 1.75 m ) and sucrose (0.05 m ). Slow cooling to 5°C improved neither fertility rate (58 vs 56% kindling rate for fast and slow cooling, respectively) nor prolificacy (6.5 vs 8.7 total born for slow and fast cooling, respectively; p < 0.05) compared to fast cooling rate to 5°C. The straw size did not have an effect on either fertility or prolificacy (47 vs 57% kindling rate and 6.3 vs 6.8 total born for sperm loaded into 0.25 and 0.5 ml straws, respectively). In addition, similar results were obtained between farms (46–57% kindling rate and 4.9–6.7 total born), although this effect should be studied further. In conclusion, with this extender, slow cooling does not present a beneficial effect on sperm fertilizing ability and either 0.25 or 0.5 ml straws can be used to freeze the sperm, obtaining similar results after artificial insemination. In addition, similar results were obtained between farms when using cryopreserved sperm, and these results were lower than those obtained after artificial insemination with fresh semen. Therefore, new approaches are needed to improve the results obtained when cryopreserved sperms are used before this type of sperm can be used for commercial purposes.