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According to the preference-performance hypothesis (PPH), also known as ‘mother-knows-best hypothesis’, herbivorous insects prefer those plants for oviposition, which yield the best offspring performance. Yet, most studies testing the PPH neglect the possibility that plant responses to insect eggs may affect both egg survival and larval performance. Here, we tested the PPH by studying responses of seven Brassicaceae plant species to oviposition by two cabbage white species. When including the egg phase, our study supports the ‘mother-knows-best hypothesis’: larvae of Pieris rapae (solitary) or P. brassicae (gregarious) gained most weight on those plant species which had received most eggs (B. nigra or B. montana, respectively). However, our experiments did not reveal any relationship between oviposition preference and egg survival. Brassicaceous species are known to respond to these butterfly eggs with a hypersensitive response (HR)-like necrosis, which can lower egg survival. Pieris eggs frequently induced necrosis in five of the tested plant species. Survival of clustered P. brassicae eggs was unaffected by HR-like in four of the five species. Therefore, our experiments did not reveal any relationship between P. brassicae egg survival and oviposition preference. Females of P. rapae preferred oviposition on plant species which most frequently showed HR-like necrosis. Remarkably, although egg survival was lower on HR-like plants, larval biomass was higher compared to plants without a necrosis. We conclude that egg survival does not seem to be a deciding factor for oviposition choices. However, egg-mediated plant responses might be important to explain the PPH of the two Pieris species.Lay summaryEgg-laying preferences of herbivorous insects can often be linked to offspring performance. Commonly, the fate of insect eggs and the plant responses to the eggs have been ignored when studying the link between preference and performance. By including the egg phase, our study supports the ‘mother-knows-best hypothesis’, explained by butterfly oviposition and associated egg and larval performances on different plant species. We especially found that egg-mediated responses seem a deciding factor for butterfly oviposition choices.

Kin selection and dispersal play a critical role in the evolution of cooperative breeding systems. Limited dispersal dramatically increases relatedness in spatially structured populations (population viscosity), with the result that neighbours tend to be genealogical relatives. Yet the increase in neighbours’ performance through altruistic interaction may also result in habitat saturation and thus exacerbate local competition between kin. Our goal was to detect the footprint of kin selection and competition by examining the spatial structure of relatedness and by comparing non-effective and effective dispersal in a population of a lekking bird,Tetrao urogallus. For this purpose, we analysed capture–recapture and genetic data collected over a 6-year period on a spatially structured population ofT. urogallusin France. Our findings revealed a strong spatial structure of relatedness in males. They also indicated that the population viscosity allowed male cooperation through two non-exclusive mechanisms. First, at their first lek attendance, males aggregate in a lek composed of relatives. Second, the distance corresponding to non-effective dispersal dramatically outweighed effective dispersal distance, which suggests that dispersers incur high post-settlement costs. These two mechanisms result in strong population genetic structuring in males. In females, our findings revealed a lower level of spatial structure of relatedness and genetic structure in respect to males. Additionally, non-effective dispersal and effective dispersal distances in females were highly similar, which suggests limited post-settlement costs. These results indicate that kin-dependent dispersal decisions and costs are factors driving the evolution of cooperative courtship and have a genetic footprint in wild populations.

Douglas fir seeds infested by diapausing larvae of a chalcid, Megastigmus spermotrophus, were transferred under different temperature and photoperiod regimes at various dates during autumn and winter. Both winter diapause and prolonged diapause were compared to the diapause patterns observed in control lots kept under natural conditions. The results showed that exposure to low temperatures in autumn and winter is required for the completion of diapause development. Median adult emergence dates and the date of transfer of larvae to 20°C were negatively correlated. The frequency of prolonged diapause of larvae transferred to 20°C decreased significantly after November. When larvae were submitted to different constant temperatures, the longer the daylength, the higher and faster the reactivation. These results suggest that chalcid larvae can perceive daylength through the seed coat. This phenomenon is probably related to the fact that most of the infested seeds falling in autumn are usually covered by a layer of leaf litter during the winter.

Ontogenetic niche shift should occur when the ratio of growth opportunities to mortality risk becomes higher in the subsequent habitat. While most studies have focused on size to understand the timing of these shifts, an endogenous factor like energetic status (interaction between energy available and energy requirements) appears as a natural candidate to integrate and analyze the growth trade-off between habitats. In this study, we measure energetic content and metabolic rate of individual brown trout (Salmo trutta) fry at emergence from gravel to investigate the influence of energetic status on the timing of this critical ontogenetic niche shift. In addition, as offspring energetic status is subject to parental effects, we examine how females could maximize their own fitness by influencing offspring emergence timing. Our results demonstrate that emergence from gravel is influenced by energetic status. Individuals that emerge first have a higher energetic content but deplete it faster because of a higher metabolic rate. We also find that female fecundity is positively related to emergence period duration. Moreover, our results suggest that females may decrease kin competition during the critical period of emergence by influencing the energetic status of offspring, thus, maximizing their own fitness. Our results help elucidate the mechanisms underlying early ontogenetic niche shifts in juvenile fish and suggest reasons why maternal investment can be so variable within populations.

Vertebrate frugivore communities are easily satiated by abundant fruit supplies and, contrary to abiotic dispersal agents, typically disperse only part of the available seed pool. This frugivore satiation is likely to be a widespread phenomenon and should be an influential predictor of plants' ability to disperse their offspring to suitable establishment sites; yet it has never been systematically quantified. Here I investigate patterns of fruit abundance, frugivore activity and frugivore satiation, and their consequences for seed dispersal in the fleshy-fruited tree Frangula alnus. Based on constant-effort seed trapping conducted over 3 years, I assess densities of total and frugivore-consumed seedfall across two spatial (within/between populations) and two temporal (within/between ripening seasons) scales. Furthermore, I examine relationships between fruit abundance and the amount of seeds that are actually dispersed away from fruiting trees. Frugivore activity tightly matched fruit abundance, although some differences existed between scales. This marked fruit tracking did not prevent a significant frugivore satiation, however, and only 53% of the available fruit crops were actually consumed. The extent of satiation varied most at the within-population level, likely due to the territorial behaviour of important frugivore species. In contrast, levels of satiation remained remarkably invariable through time, suggesting that frugivores behave as opportunists and closely adjust the composition of their diet to the available food supply. Overall, greater fruit abundance resulted in a higher proportion of seeds falling beneath fruiting trees, but it also helped increase the (absolute) number of seeds dispersed. This study shows that frugivore satiation can be an important phenomenon even when frugivores tightly track fruit abundance. Its negative effects on recruitment may be attenuated, however, if greater fruit crops help increase population-wide frugivore activity and the amount of seeds being dispersed to suitable establishment sites. © 2008 Springer-Verlag.

International audience; The stable C isotope composition (delta13C) of CO2 respired by trunks was examined in a mature temperate deciduous oak forest (Quercus petraea). Month-to-month, day-to-day and diurnal, measurements were made to determine the range of variations at different temporal scales. Trunk growth and respiration rates were assessed. Phloem tissue was sampled and was analysed for total organic matter and soluble sugar 13C composition. The CO2 respired by trunk was always enriched in 13C relative to the total organic matter, sometimes by as much as 5 per thousand. The delta13C of respired CO2 exhibited a large seasonal variation (3.3 per thousand), with a relative maximum at the beginning of the growth period. The lowest values occurred in summer when the respiration rates were maximal. After the cessation of radial trunk growth, the respired CO2 delta13C values showed a progressive increase, which was linked to a parallel increase in soluble sugar content in the phloem tissue (R=0.95; P

International audience; Interspecific interactions can vary within and among populations and geographic locations, and this variation can influence the nature of the interaction (e.g. mutualistic vs. antagonistic) and its evolutionary stability. Globeflowers are exclusively pollinated by flies, whose larvae feed only on their seeds. Here we document geographic variability in costs and benefits in globeflowers in sustaining their pollinating flies throughout the range of this arctic-alpine European plant over several years. A total of 1,710 flower heads from 38 populations were analysed for their carpel, egg and seed contents. Individual and population analyses control for the confounding influences of variation in both: (1) population traits, such as fly density and egg distribution among flower heads; and (2) individuals traits, such as carpel and egg numbers per flower head. Despite considerable variation in ecological conditions and pollinator densities across populations, large proportions (range 33-58%) of seeds were released after predation, with a benefit-to-cost ratio of 3, indicating that the mutualism is stable over the whole globeflower geographical range. The stability of the mutualistic interaction relies on density-dependent competition among larvae co-developing in a flower head. This competition is revealed by a sharp decrease in the number of seeds eaten per larva with increasing larval number, and is intensified by non-uniform egg distribution among globeflowers within a population. Carpel number is highly variable across globeflowers (range 10-69), and flies lay more eggs in large flowers. Most plants within a population contribute to the rearing of pollinators, but the costs are greater for some than for others. Large globeflowers lose more seed to pollinator larvae, but also release more seed than smaller plants. The apparent alignment of interests between fly and plants (positive relationship between numbers of seed released and destroyed) is shown to hide a conflict of interest found when flower size is controlled for.

International audience; We investigated the metapopulation genetic structure of two specialist parasitoids, Cotesia melitaearum and Hyposoter horticola, attacking the Glanville fritillary butterfly (Melitaea cinxia) in the Åland Islands south-western Finland. The host butterfly persists as a classic metapopulation in a network of 4,000 small habitat patches within an area of 50 by 70 km . The two parasitoids are known to differ greatly in their population dynamics and spatial pattern of occupancy in local host populations. Analysis of genetic population structure using FST and clustering of multilocus genotypes revealed a distinct large-scale spatial structure in C. melitaearum but a very weak pattern in H. horticola. This result is consistent with the known difference in the dispersal range (much longer in H. horticola) and population size (much greater in H. horticola) of the two parasitoids.

We report here the first case of queen dimorphism in a ponerine ant species. A total of 550 colonies of the Neotropical ponerine ant Ectatomma ruidum, from two natural populations in southeastern Mexico, were investigated for polymorphism and reproductive function within the queen caste. The distribution of different morphological traits (head and thorax widths, and scutum and alitrunk lengths) was shown to be bimodal. Thorax width and head width were significantly isometric for both macro- and microgynes and thorax proportions did not change with the category of the queen. Microgynes appear as an isometric reduction of the normal queens. On average, macrogynes were found to be approximately 20% larger in size and twice as heavy as microgynes (and up to three times heavier in terms of dry weight). Their wing surface was 72% greater. There was no difference between the two morphs in terms of their capacity to be inseminated and all dealate females present in natural colonies could be considered as true potentially reproductive queens whatever the class to which they belonged. Ovary size, number of ovarioles per ovary, and number of mature oocytes produced were significantly higher for macrogynes than for microgynes, but small queens were able to function as active egg-layers. However, the number of egg-laying individuals was significantly lower for this form, although egg-laying activity appeared to be independent of queen weight. Despite its markedly reduced reproductive capacity compared to macrogynes, the distribution of the microgyne form of E. ruidum in both studied populations was very broad, reaching one-third of all alate and dealate females and extending to one-third of all colonies. In 72.2% of the colonies where alate and/or dealate microgynes were present, both forms co-occurred. Fat content analysis results supported the idea that semi-claustral independent colony founding, typical for this species, would essentially be achieved by macrogynes, while microgynes would be adopted by established colonies. We argue that queen dimorphism in E. ruidum could represent an attractive alternative dispersal strategy for female sexuals. The small females may constitute an important reserve of potential reproductives at a very low energetic cost to the colony, the production of a macrogyne being about 7.5 times more costly than a microgyne. The significantly greater `wing surface/body weight' ratio of microgynes also suggests their greater capacity for dispersion. The combination of such a capacity for microgynes, along with their ability to contribute in the production of both female morphs, including the reproductively efficient macrogynes, would contribute to insuring genetic reassortment at the population level and could explain, in part, the ecological success of E. ruidum in Neotropical zones.

International audience; The effects of several environmental factors on the postweaning growth of wild Alpine marmots were investigated. Factors considered were year of birth, sun exposure in the home range, litter size, and sex of young, Components of growth were juvenile mass at emergence from the natal burrow (as a result of preweaning growth) and postweaning growth rate. We also considered the length of the active season during which growth occurs. Mass at emergence and postweaning growth rate varied according to year of birth, were higher in south-facing than in north-facing home ranges, and were higher in small litters. Mass at emergence was higher for males than for females. We suggest that environmental factors affected the juvenile growth pattern through influences on maternal body condition. Our results support Trombulak's hypothesis that mothers maintain as many young as physiologically possible. We suggest that mothers in poor condition sacrificed the mass of their offspring rather than their number. A body mass sexual dimorphism of juveniles occurred at emergence, suggesting that mothers may provide more care for their male than their female offspring.

The possibility of ecosystem boundary changes in northern Brazilian Amazonia during the Holocene period was investigated using soil organic carbon isotope ratios. Determination of past and present fluctuations of the forest-savanna boundary involved the measurement of natural 13C isotope abundance, expressed as delta 13C, in soil organic matter (SOM). SOM 13C analyses and radiocarbon dating of charcoal fragments were carried out on samples derived from soil profiles taken along transects perpendicular to the ecotonal boundary. SOM delta 13C values in the upper soil horizons appeared to be in equilibrium with the overlying vegetation types and did not point to a movement of the boundary during the last decades. However, delta 13C values obtained from deeper savanna and forest soil layers indicated that the vegetation type has changed in the past. In current savanna soil profiles, we observed the presence of mid-Holocene charcoals derived from forest species : fire frequency at that time was probably greater, and more extensive savanna may have resulted. Isotope data and the presence of these charcoals thus suggest that the forest-savanna boundary has shifted significantly in the recent Holocene period, forest being more extensive during the early Holocene than today. During the middle Holocene, the forest could have strongly regressed, and fires appeared, with a maximum development of the savanna vegetation. At the beginning of the late Holocene, the forest may have invaded a part of this savanna, and fires occurred again. (Résumé d'auteur)

This study evaluated one semi-direct and three indirect methods for estimating leaf area index (LAI) by comparing these estimates with direct estimates derived from litter collection. The semi-direct method uses a thin metallic needle to count a number of contacts across fresh litter layers. One indirect method is based on the penetration of diffuse global radiation measured over the course of a day. The second indirect method uses the LAI-2000 plant canopy analyser (PCA) which measures diffuse light penetration from five different sky sectors simultaneously. The third indirect method uses the "Demon" portable light sensor to measure the penetration of direct beam sunlight at different zenith angles over the course of half a day. The Poisson model of gap frequency was applied to estimate plant area index (PAI) from observed transmittances using the second and third methods. Litter collection from 11 temperate decidous forests gave values of LAI ranging from 1.7 to 7.5. Estimates based on the needle method showed a significant linear relationship with LAI values obtained from litter collections but were systematically lower (by 6-37%). PAI estimates using all three indirect techniques (fixed light sensor system, LAI-2000 and Demon) showed a strong linear relationship with LAI derived from litter collection. Differences, averaged over all forest stands, between PAI estimates from each of the three indirect methods and LAI from litter collections were below 2%. If we consider that LAI=PAI-WAI (wood area index) then, all three indirect methods underestimated LAI by an additional factor close to the value of WAI. One reason could be a local clumping of architectural canopy components: in particular, the spatial dispositions of branchlets and leaves are not independent, leading to a non-random relationship between the distributions of these two canopy components.

International audience; Myrmecophytic symbioses are widespread in tropical ecosystems and their diversity makes them useful tools for understanding the origin and evolution of mutualisms. Obligate ant–plants, or myrmecophytes, provide a nesting place, and, often, food to a limited number of plant–ant species. In exchange, plant–ants protect their host plants from herbivores, competitors and pathogens, and can provide them with nutrients. Although most studies to date have highlighted a similar global pattern of interactions in these systems, little is known about the temporal structuring and dynamics of most of these associations. In this study we focused on the association between the understory myrmecophyte Hirtella physophora (Chrysobalanaceae) and its obligate ant partner Allomerus decemarticulatus (Myrmicinae). An examination of the life histories and growth rates of both partners demonstrated that this plant species has a much longer lifespan (up to about 350 years) than its associated ant colonies (up to about 21 years). The size of the ant colonies and their reproductive success were strongly limited by the available nesting space provided by the host plants. Moreover, the resident ants positively affected the vegetative growth of their host plant, but had a negative effect on its reproduction by reducing the number of flowers and fruits by more than 50%. Altogether our results are important to understanding the evolutionary dynamics of ant–plant symbioses. The highly specialized interaction between long-lived plants and ants with a shorter lifespan produces an asymmetry in the evolutionary rates of the interaction which, in return, can affect the degree to which the interests of the two partners converge.

International audience; Fertilisation of agricultural land causes an accumulation of nutrients in the top soil layer, among which phosphorus (P) is particularly persistent. Changing land use from farmland to forest affects soil properties, but changes in P pools have rarely been studied despite their importance to forest ecosystem development. Here, we describe the redistributions of the P pools in a four-decadal chronosequence of post-agricultural common oak (Quercus robur L.) forests in Belgium and Denmark. The aim was to assess whether forest age causes a repartitioning of P throughout the various soil P pools (labile P, slowly cycling P and occluded P); in particular, we addressed the time-related alterations in the inorganic versus organic P fractions. In less than 40 years of oak forest development, significant redistributions have occurred between different P fractions. While both the labile and the slowly cycling inorganic P fractions significantly decreased with forest age, the organic fractions significantly increased. The labile P pool (inorganic + organic), which is considered to be the pool of P most likely to contribute to plant-available P, significantly decreased with forest age (from >20 to

International audience; Tradeoffs between current reproduction andfuture survival are widely recognized, but may only occurwhen food is limited: when foraging conditions arefavorable, parents may be able to reproduce withoutcompromising their own survival. We investigated thesetradeoffs in the little auk (Alle alle), a small seabird with asingle-egg clutch. During 2005–2007, we examined therelationship between body mass and survival of birdsbreeding under contrasting foraging conditions at twoArctic colonies. We used corticosterone levels of breedingadults as a physiological indicator of the foraging conditionsthey encountered during each reproductive season.We found that when foraging conditions were relativelypoor (as reflected in elevated levels of corticosterone),parents ended the reproductive season with low body massand suffered increased post-breeding mortality. A positiverelationship between body mass and post-breeding survivalwas found in one study year; light birds incurred highersurvival costs than heavy birds. The results of this studysuggest that reproducing under poor foraging conditionsmay affect the post-breeding survival of long-lived littleauks. They also have important demographic implicationsbecause even a small change in adult survival may have alarge effect on populations of long-lived species.

A comparative study was conducted on the recruitment patterns of two non-pioneer tree species, one dispersed by arboreal mammals and birds (Virola michelii, Myristicaceae) and the other by rodents (Moronobea coccinea, Clusiaceae). These species differ in fruiting phenology, seed size, dispersal distance, germination time and seed nutrient exhaustion. In both species, establishment patterns were consistent with the escape hypothesis and the Janzen-Connell model. Virola seeds need not be buried to survive and germinate, and may produce a seedling carpet beneath the parent. Moronobea seedlings only establish from seeds buried by scatterhoarding rodents in the surrounding understory. One-year survival of Virola seedlings was 47.8% and was greater >10 m than < 10 m from the largest parent tree. In contrast, survival of Moronobea seedlings was 56% 3 years after seed dispersal. Survival of juveniles was greater in gaps than in the understory for Virola but not for Moronobea. Moronobea survival was greater than Virola survival in both microhabitats. Both species establish in the understory, yet both grew faster in gaps. Virola appeared to be more gap-dependent than Moronobea which may persist several years in the understory until a gap occurs. Virola and Moronobea illustrate two intermediate recruitment patterns along an hypothetical continuum of nonpioneer species replacement (Bazzaz and Pickett 1980; Swaine and Whitmore 1988).

Converting deciduous forests to coniferous plantations and vice versa causes environmental changes, but till now insight into the overall effect is lacking. This review, based on 38 case studies, aims to find out how coniferous and deciduous forests differ in terms of throughfall (+stemflow) deposition and seepage flux to groundwater. From the comparison of coniferous and deciduous stands at comparable sites, it can be inferred that deciduous forests receive less N and S via throughfall (+stemflow) deposition on the forest floor. In regions with relatively low open field deposition of atmospheric N (10 kg N ha(-1) year(-1)), lower NH(4)(+) mean throughfall (+stemflow) deposition was, however, reported under conifers compared to deciduous forest, while in regions with high atmospheric N pollution (10 kg N ha(-1) year(-1)), the opposite could be concluded. The higher the open field deposition of NH(4)(+), the bigger the difference between the coniferous and deciduous throughfall (+stemflow) deposition. Furthermore, it can be concluded that canopy exchange of K(+), Ca(2+) and Mg(2+) is on average higher in deciduous stands. The significantly higher stand deposition flux of N and S in coniferous forests is reflected in a higher soil seepage flux of NO(3)(-), SO(4)(2-), K(+), Ca(2+), Mg(2+) and Al(III). Considering a subset of papers for which all necessary data were available, a close relationship between throughfall (+stemflow) deposition and seepage was found for N, irrespective of the forest type, while this was not the case for S. This review shows that the higher input flux of N and S in coniferous forests clearly involves a higher seepage of NO(3)(-) and SO(4)(2-) and accompanying cations K(+), Ca(2+), Mg(2+) and Al(III) into the groundwater, making this forest type more vulnerable to acidification and eutrophication compared to the deciduous forest type.

Like other pond-breeding amphibians, the natterjack toad (Bufo calamita) typically presents a patchy distribution. Because the species experiences high probabilities of local population extinction, its persistence within landscapes relies on both local and landscape-scale processes [dispersal allowing the (re)colonization of habitat patches]. However, the structure and composition of the matrix surrounding local populations can alter the dispersal rates between populations. As shown previously (Landscape Ecol 19:829-842, 2004), the locomotor performances of individuals at the dispersal stage depend on the nature of the component crossed: some landscape components offer high resistance to movement (high resistance or high viscosity components) whereas others allow high efficiency of movement (low resistance components). We now examine the ability of individuals to discriminate between landscape components and select low-resistance components. Our experimental study investigates the ways in which young natterjack toads choose from among landscape components common to southern Belgium. Toadlets (the dispersal stage) were experimentally confronted with boundaries between surrogates of sandy soils, roads, forests, agricultural fields and intensive pastures. Our results show: 1 the ability of toadlets to react to boundaries between landscape components, 2 differences in permeability among boundaries, and 3 our inability to predict correctly the permeability of the boundaries from the patch-specific resistance assessed previously. Toadlets showed a preference for bare environments and forests, whereas they avoided the use of agricultural environments. This pattern could not be explained in terms of patch-specific resistance only, and is discussed in terms of mortality risks and resource availability in the various landscape components, with particular attention to repercussions on conservation strategies.

During microbial breakdown of leaf litter a fraction of the C lost by the litter is not released to the atmosphere as CO(2) but remains in the soil as microbial byproducts. The amount of this fraction and the factors influencing its size are not yet clearly known. We performed a laboratory experiment to quantify the flow of C from decaying litter into the soil, by means of stable C isotopes, and tested its dependence on litter chemical properties. Three sets of (13)C-depleted leaf litter (Liquidambar styraciflua L., Cercis canadensis L. and Pinus taeda L.) were incubated in the laboratory in jars containing (13)C-enriched soil (i.e. formed C4 vegetation). Four jars containing soil only were used as a control. Litter chemical properties were measured using thermogravimetry (Tg) and pyrolysis-gas chromatography/mass spectrometry-combustion interface-isotope ratio mass spectrometry (Py-GC/MS-C-IRMS). The respiration rates and the delta(13)C of the respired CO(2) were measured at regular intervals. After 8 months of incubation, soils incubated with both L. styraciflua and C. canadensis showed a significant change in delta(13)C (delta(13)C(final) = -20.2 +/- 0.4 per thousand and -19.5 +/- 0.5 per thousand, respectively) with respect to the initial value (delta(13)C(initial) = -17.7 +/- 0.3 per thousand); the same did not hold for soil incubated with P. taeda (delta(13)C(final:)-18.1 +/- 0.5 per thousand). The percentages of litter-derived C in soil over the total C loss were not statistically different from one litter species to another. This suggests that there is no dependence of the percentage of C input into the soil (over the total C loss) on litter quality and that the fractional loss of leaf litter C is dependent only on the microbial assimilation efficiency. The percentage of litter-derived C in soil was estimated to be 13 +/- 3% of total C loss.

International audience; The European grapevine moth, Lobesia botrana is a major grapevine pest, but despite the abundance of vineyards it is a generalist and uses either grapes or alternative species. Given the abundance and predictability of grape, L. botrana could be expected to have evolved towards monophagy. In order to understand why this species remains polyphagous, we hypothesized that larvae reared on rare wild host plants should have higher fitness than those reared on the more abundant grape host. For this, we compared larval performance and several life history traits on three alternative host plants (Daphne gnidium, Olea europaea, Tanacetum vulgare) and three Vitaceae (Vitis vinifera), two cultivars and one wild species (Ampelopsis brevipedunculata), and two control groups raised on either a low or a high nutritive value medium. Alternative hosts are more suitable than Vitaceae for the reproductive performance of L. botrana: larval mortality and development time was reduced, while pupal weight, growth rate, female longevity, female fecundity, duration of laying and mating success were increased. High quality food ingested by larvae promotes higher adult body weight and enhances female reproductive output. This suggests that alternative hosts provide greater nutritional value for L. botrana than Vitaceae. The use of alternative host plants could thus be maintained in the host range because they offer L. botrana a better fitness than on the Vitaceae. This could typically represent an advantage for moths behaving in plant diversity grape landscapes.

International audience; The effect of experimental manipulation of population density on home-range size was investigated in two free-ranging roe deer (Capreolus capreolus) populations under contrasting environmental conditions. In these two long-term monitoring studies, one in Bogesund, Sweden (12 years) and one in Dourdan, France (10 years), deer density varied fourfold through varying culling pressure. Home-range data were collected by radio-tracking across the periods of contrasting density of the studies. We predicted that home-range size for females should vary in relation to the level of feeding competition, while for males, competition for mating opportunities should also influence range size, at least in summer when roe bucks are territorial. We found a highly consistent pattern over the two populations, with strong effects of deer density on home-range size, as well as significant differences between winter and summer ranges and between the sexes. Home ranges were consistently smaller at high density compared to low density. Males had larger ranges than females and this was particularly so during summer. Lastly, winter ranges were generally larger than summer ranges, particularly among females, although males at Dourdan had larger summer ranges compared to winter ranges. We suggest that the reduction of range size at high deer density during winter, as well as summer, is linked to the solitary behaviour and territorial social system of roe deer, with possible effects of dominance rank, even outside the mating season

International audience; Some plants are exclusively pollinated by an insect whose larvae feed on their seeds. The net outcome of a single visit for the plant depends on the number of ovules fertilised by the visitor, the number of eggs laid, and the number of seeds eaten by each larva. Unlike other known plant-seed eater pollinating mutualisms, the globeflower-globeflower fly mutualism (Trollius europaeus-Chiastocheta spp.) is unique in that not only females but also males visit flowers, and both sexes are potential pollinators. I analysed the relative efficiency of Chiastocheta males versus females in transporting pollen and fertilising globeflower ovules. I show that there is no sex-specific morphological adaptation or behaviour to enhance pollen collection and transportation in Chiastocheta flies, and that males contribute to pollination. However, because of their smaller body size, males transport significantly less pollen than females. Less seeds are produced after a visit from a male than after a visit from a female. A single female visit contributes to about 12% of total seed production, and a single male visit to only 5.4%. Females tend to spend more time inside the flower than males, and the number of ovules fertilised is significantly correlated with the time insects spent inside the closed corolla. The lower efficiency of ovule fertilisation by a male's single visit is compensated for by the higher rate of flower visitation by males: a flower receives about twice as many visits from males as from females during a time unit. The contribution of males to pollination is of major importance with respect to understanding the evolutionary stability of the globeflower-globeflower fly mutualism, as males satiate pollen requirement of flowers, masking the antagonistic effect of ovipositing females.

International audience; Plants sense the presence of neighbouring vegetation through phytochrome photoreceptors perceiving a lowered red to far-red ratio (R:FR) of light reflected from such vegetation. We hypothesised that it would be advantageous for the grassland clonal herb, Trifolium repens, to have an inhibitory branching response to perception by leaves of light reflected from neighbouring vegetation (i.e. light with lowered R:FR ratio) but have no response to interception of such light by the plagiotropic stem. We tested whether photoreception of reflected light by plagiotropic stems resulted in a different branching response to photoreception by leaves and whether leaf ontogeny influenced the response. To simulate light reflected from vegetation, FR light-emitting-diodes were used to supplement controlled environment room Light so that the R:FR ratio, but not the photosynthetic photon fluence rate, of light incident at the stem or leaf of a phytomer of T. repens was lowered from 1.20 to 0.25. The plagiotropic stems were unresponsive to light simulating that reflected from vegetation. This response differs from that of stems of orthotropic species, indicating that plagiotropic stems have evolved an organ-specific photobiology. Treatment of the mature leaf with light of lowered FR ratio reduced phytomer production only of the branch in the axil of the treated leaf. Similar treatment of the immature leaf retarded, in addition, branching at basal phytomers on the same side of the primary stem axis. Thus the response to light simulating that reflected from neighbouring vegetation depended upon whether the light was incident at the stem or the leaf and on the stage of leaf development. We argue that such responses improve the performance and fitness of T. repens within grassland habitats by allowing axillary buds on plagiotropic stems to branch freely when stems are in receipt of Light reflected from vegetation while leaves are in full light.

In tropical rain forests of Central America, the canopy tree Dipteryx panamensis (Papilionaceae) fruits when overall fruit biomass is low for mammals. Flying and arboreal consumers feed on D. panamensis and drop seeds under the parent or disperse them farther away. Seeds on the ground attract many vertebrate seed-eaters, some of them potential secondary seed dispersers. The fate of seeds artificially distributed to simulate bat dispersal was studied in relation to fruitfall periodicity and the visiting frequency of diurnal rodents at Barro Colorado Island (BCI), Panama. The frequency of visits by agoutis is very high at the beginning of fruitfall, but in the area close (50 m) to fruiting trees (Dipteryx-rich area) it declines throughout fruiting, whereas it remains unchanged farther (50 m) away (Dipteryx-poor and Gustavia-rich area). Squirrels were usually observed in the Dipteryx-rich area. Along with intense post-dispersal seed predation by rodents in the Dipteryx-rich area, a significant proportion of seeds were cached by rodents in the Dipteryx-poor area. Post-dispersal seed predation rate was inversely related to hoarding rate. A significantly greater proportion of seeds was cached in March, especially more than 100 m from the nearest fruiting tree. This correlates with the mid-fruiting period, i.e. during the height of D. panamensis fruiting, when rodents seem to be temporarily satiated with the food supply at parent trees. Hoarding remained high toward April, i.e. late in the fruiting season of D. panamensis. Low survival of scatterhoarded seeds suggests that the alternative food supply over the animal's home-ranges in May-June 1990 was too low to promote survival of cached seeds. Seedlings are assumed to establish in the less-used area of the rodents' home-range when overall food supply is sufficient to satiate post-dispersal predators.

SCOPUS: ar.j, info:eu-repo/semantics/published