Conserved oviposition preferences in alpine leaf beetle populations despite host shifts and isolation

Abstract.  1. Choosing the plant on which to lay their eggs is the last act of care that most female herbivorous insects bestow upon their offspring. These decisions play a pivotal role in insect–plant interactions, placing host preference under strong selection and contributing to the diversity of phytophagous insects as one of the first traits to adapt to new hosts.
2. This study presents a test of whether extreme isolation and exposure to different host plants can produce intra-specific divergence in oviposition preference in alpine insects. Geographic variation should impose selection to fine-tune host plant ranking and specificity to the plants normally encountered, to avoid wasting time during the very limited reproductive season experienced at high altitudes.
3. Beetles from five populations of Oreina elongata differing in host availability were offered three natural hosts: Cirsium spinosissimum , Adenostyles alliariae , and Adenostyles glabra . A novel application of a continuation ratio model (logistic regression) was made to sequential no-choice experiments, combined with quasi-likelihood analysis of multiple-choice experiments.
4. The results show little geographic variation in host plant choice: all populations strongly preferred Cirsium in multiple-choice trials, and in no-choice experiments laid around 47% of their remaining eggs during each stage, almost regardless of the host present.
5. Enemy-free space seems to explain the preference for Cirsium , but isolation and exposure to different plants has clearly not caused local adaptation in host plant ranking or specificity. Reasons for this conservatism despite divergence in other characteristics are discussed.     

Effect of Post-anthesis Drought on Cell Division and Starch Accumulation in Developing Wheat Grains

Wheat plants (Triticum aestivum L., cv. Warigal) were subjectedto 20 d of water deficit during the period of endosperm celldivision. Drought accentuated the differences in final grainweight between spikelets and between grains within spikelets.The distal grains of top spikelets were most affected by drought.The maximum number of endosperm cells was, respectively, 30and 40 per cent lower in basal grains and distal grains of draughtedplants. In basal grains of middle spikelets, the number of largestarch granules per cell was unaffected but the number of smallstarch granules per cell was 45 per cent lower in grains ofdraughted plants. The initiation of small starch granules wasmore affected than cell division because severe water deficitoccurred earlier during the former process than the latter.Final dry weight appeared to correlate well with the maximumnumber of endosperm cells, but depended also on the number ofstarch granules per cell. Consequently, the amount of dry matterper cell was not constant in both treatments. The concentration of sucrose per endosperm cell was lower onlyin the droughted distal grains of top spikelets. The supplyof sucrose to endosperm cells did not regulate the initiationof small starch granules. Triticum aestivum L., wheat, drought, grain growth, cell division, starch     

Efficacy of Bacillus sphaericus 2362 against larvae of Anopheles gambiae under laboratory and field conditions in West Africa

A flowable concentrate of Bacillus sphaericus (Neide) strain 2362 was applied against Anopheles gambiae Giles s.l. mosquito larve in small plot field trials in Bobo-Dioulasso area. Burkina-Faso. Third and fourth instar larvae were controlled for 10-15 days with a dosage of 10 g/m2, 3-10 days with 1 or 0.1 mg/m2, and 2 days with 0.01 g/m2. Complete elimination of larval populations required 1 x 10(2) to 2 x 10(3) viable spores/ml in the larval feeding zone. After treatment, the total numbers of viable spores decreased in the ponds, due to ingestion of spores by non-target as well as target organisms and/or loss of viability of some spores by sunlight. This formulation was less effective against An. gambiae than against Culex quinquefasciatus Say larvae, both in laboratory bioassays and under field conditions.     

Modelling the hydraulic preferences of benthic macroinvertebrates in small European streams

1. Relating processes occurring at a local scale to the natural variability of ecosystems at a larger scale requires the design of predictive models both to orientate stream management and to predict the effects of larger scale disturbances such as climate changes. Our study contributes to this effort by providing detailed models of the hydraulic preferences of 151 invertebrate taxa, mostly identified at the species level. We used an extensive data set comprising 580 invertebrate samples collected using a Surber net from nine sites of second and third order streams during one, two or three surveys at each site. We used nested non‐linear mixed models to relate taxon local densities to bed shear stresses estimated from FliesswasserStammTisch hemisphere numbers. 2. An average model by taxon, i.e. independent from surveys, globally explained 25% of the density variations of taxa within surveys. A quadratic relationship existed between the average preferences and the niche breadth of taxa, indicating that taxa preferring extreme hemisphere numbers had a reduced hydraulic niche breadth. A more complete model, where taxa preferences vary across surveys, globally explained 38% of the variation of taxa densities within surveys. Variations in preferences across surveys were weak for taxa preferring extreme hemisphere numbers. 3. There was a significant taxonomic effect on preferences computed from the complete model. By contrast, season, site, average hemisphere number within a survey and average density of taxa within a survey used as covariates did not consistently explain shifts in taxon hydraulic preferences across surveys. 4. The average hydraulic preferences of taxa obtained from the extensive data set were well correlated to those obtained from two additional independent data sets collected in other regions. The consistency of taxon preferences across regions supports the use of regional preference curves for estimating the impact of river management on invertebrate communities. By contrast, the hydraulic niche breadths of taxa computed from the different data sets were not related.     

Individual acoustic monitoring of the European Eagle Owl Bubo bubo

The Eagle Owl Bubo bubo is cited in Annex I of the Birds Directive of the European Union. Europe's biggest owl is extremely sensitive to human presence and needs special conservation measures. The present paper aims to show that monitoring of individuals by bioacoustic methods can be relevant to understanding population dynamics. Our study investigates the possibility of identifying a vocal signature in the wild-recorded calls of male and female Eagle Owls, and assesses the potential use of these signatures for long-term monitoring of individuals in the field. We show that both males and females of a given population can be identified individually on the basis of their calls. Our results also show that, regardless of the sex, most of the individuals recorded in the first year of the investigation may be identical to those recorded in the same places the year after. This bioacoustic approach could thus be used in studies of site fidelity.     

Interspecific variation in neighbour–stranger discrimination in ants of the Neoponera apicalis complex

1. The ecological success of social insects lies in their ability to prevent the exploitation of colony resources by competitors or parasites. Nestmate recognition is therefore of crucial importance in maintaining the integrity of the colony. Furthermore, inter‐colony competitive relationships are often complex, as many species discriminate between neighbours and strangers, with reduced (the dear enemy phenomenon) or increased levels of aggression towards nearby colonies, depending on the species. In this context, between‐species comparisons could be particularly helpful to investigate the proximate causes underlying this context‐dependent phenomenon, but these are notoriously lacking. 2. Here an attempt was made to circumvent this drawback by studying three closely related sympatric ant species with very similar life histories that belong to the Neoponera apicalis complex. The present study investigated how nestmate recognition and inter‐colony competitive relationships were influenced by spatial, chemical and genetic distances between colonies. 3. It was found that one species, N. apicalis morph 7, showed a clear dear enemy phenomenon with no influence of chemical and genetic distances, suggesting the existence of a learning process. In contrast, N. apicalis morph 4 and Neoponera verenae morph 1 failed to show any strong discrimination between close and distant non‐nestmates. 4. These results are discussed in the light of the observed interspecific variation in nesting preferences, possibly constraining the opportunities of familiarisation between nearby nests, and modulating the competition for resources between colonies. 5. It is argued that this study further reinforces the relative threat level hypothesis as an ultimate explanation for neighbour–stranger discrimination processes.     

Bud-burst modelling in Siberia and its impact on quantifying the carbon budget

Vegetation phenology is affected by climate change and in turn feeds back on climate by affecting the annual carbon uptake by vegetation. To quantify the impact of phenology on terrestrial carbon fluxes, we calibrate a bud‐burst model and embed it in the Sheffield dynamic global vegetation model (SDGVM) in order to perform carbon budget calculations. Bud‐burst dates derived from the VEGETATION sensor onboard the SPOT‐4 satellite are used to calibrate a range of bud‐burst models. This dataset has been recently developed using a new methodology based on the normalized difference water index, which is able to distinguish snowmelt from the onset of vegetation activity after winter. After calibration, a simple spring warming model was found to perform as well as more complex models accounting for a chilling requirement, and hence it was used for the carbon flux calculations. The root mean square difference (RMSD) between the calibrated model and the VEGETATION dataset was 6.5 days, and was 6.9 days between the calibrated model and independent ground observations of bud‐burst available at nine locations over Siberia. The effects of bud‐burst model uncertainties on the carbon budget were evaluated using the SDGVM. The 6.5 days RMSD in the bud‐burst date (a 6% variation in the growing season length), treated as a random noise, translates into about 41 g cm^?2 yr^?1 in net primary production (NPP), which corresponds to 8% of the mean NPP. This is a moderate impact and suggests the calibrated model is accurate enough for carbon budget calculations. In addition to random differences between the calibrated model and VEGETATION data, systematic errors between the calibrated bud‐burst model and true ground behaviour may occur, because of bias in the temperature dataset or because the bud‐burst detected by VEGETATION is because of some other phenological indicator. A systematic error of 1 day in bud‐burst translates into a 10 g cm^?2 yr^?1 error in NPP (about 2%). Based on the limited available ground data, any systematic error because of the use of VEGETATION data should not lead to significant errors in the calculated carbon flux. In contrast, widely used methods based on the normalized difference vegetation index from the advanced very high resolution radiometer satellite are likely to confuse snowmelt and vegetation greening, leading to errors of up to 15 days in bud‐burst date, with consequent large errors in carbon flux calculations.     

Temporally stable genetic variability and dynamic kinship structure in a fluctuating population of the root vole Microtus oeconomus

Genetic variability, kin structure and demography of a population are mutually dependent. Population genetic theory predicts that under demographically stable conditions, neutral genetic variability reaches equilibrium between gene flow and drift. However, density fluctuations and non‐random mating, resulting e.g. from kin clustering, may lead to changes in genetic composition over time. Theoretical models also predict that changes in kin structure may affect aggression level and recruitment, leading to density fluctuations. These predictions have been rarely tested in natural populations. The aim of this study was to analyse changes in genetic variability and kin structure in a local population of the root vole (Microtus oeconomus) that underwent a fourfold change in mean density over a 6‐year period. Intensive live‐trapping resulted in sampling 88% of individuals present in the study area, as estimated from mark–recapture data. Based on 642 individual genotypes at 20 microsatellite loci, we compared genetic variability and kin structure of this population between consecutive years. We found that immigration was negatively correlated with density, while the number of kin groups was positively correlated with density. This is consistent with theoretical predictions that changes in kin structure play an important role in population fluctuations. Despite the changes in density and kin structure, there was no genetic differentiation between years. Population‐level genetic diversity measures did not significantly vary in time and remained relatively high (H_E range: 0.72–0.78). These results show that a population that undergoes significant demographic and social changes may maintain high genetic variability and stable genetic composition.     

Invertebrate hydraulic preferences and predicted impacts of changes in discharge in a large river

• 1 Instream habitat models are attractive tools for assessing the impacts of flow restoration on aquatic organisms, but have been rarely used for invertebrates due to the lack of knowledge of their hydraulic preferences.
• 2 In this study, we provide quantitative models of the hydraulic preferences for 66 invertebrate taxa found in the Upper Rhône River (France), and combine these preferences with a statistical habitat model (FSTress) to predict the effects of minimum flow restoration on invertebrate abundances in two bypassed sections of the river.
• 3 Many taxa show marked preferences for particular hydraulic conditions. Average preferred hydraulic conditions were significantly related to those observed in smaller streams (R² = 0.37).
• 4 Our model predicted that habitat values of 27 taxa should be enhanced by restoration operations, but also predicted a decrease of habitat values in the main channel for 12 limnophilic taxa. However, these taxa are expected to maintain populations by finding refuges in restored cut‐off channels and overall invertebrate diversity is predicted to increase in the two bypassed sections studied here.