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Sugarcane (Poaceae) has not undergone any commercial selection based upon seed characteristics. As the plant is grown from vegetative cuttings and the stalk harvested for its sucrose content, relatively little is known about its seed compared with other grass crops. The seeds of sugarcane were small, 1.8 x 0.8 mm, and the embryo comprised about one-third of the seed volume. Among the samples analysed, the seed contained on average 37%, 20% and 10% of the fresh weight as starch, protein and lipid, respectively. Histochemical staining showed that the starch was confined to the endosperm and the lipid to the embryo and aleurone layer. Protein was found in the embryo, endosperm and aleurone layer. There were small but significant differences between the sources of sugarcane seed. The wild relative S. spontaneum had significantly less starch than the commercial hybrid sugarcane seed. The lipid content was higher for sugarcane seed than for the seeds of many other grasses, possibly because of the high ratio of lipid-containing embryo to endosperm. Following artificial ageing, the observed decline in seed viability was not closely reflected by any significant changes in composition, although protein and sugars were reduced after 168 h. These results contribute to our understanding of the sexual reproductive biology of sugarcane, which is important for the science-based environmental risk evaluation of the release of genetically modified sugarcane. [ABSTRACT FROM AUTHOR]

Pastoralism impacts the habitat quality of wild animals, while poaching is a direct threat to populations. The demographic effects of pastoralism are well known, whereas the effects of poaching are difficult to obtain. In addition, little attention has been paid to the role of tourism as a facilitator of poaching, especially when tourists feed animals and thus lower their fear of humans. In this paper, we investigate the demographic effects of pastoralism (a habitat quality indicator) and tourism (a poaching indicator) on wild Barbary macaques ( Macaca sylvanus) in Middle Atlas ( Morocco). Neither pastoralism nor tourism affected reproduction rates. High tourism pressure was related to a dramatic deficit in immature individuals. In groups near tourist sites, about half of the infants disappeared suggesting a high poaching pressure on these groups; as poachers select infants to sell as pets, infants used to seeing tourists probably constitute easy poaching targets. Group size and age structure were unrelated to the intensity of pastoralism. Groups were then half the size of those in undisturbed forests and in Middle Atlas 30 years ago. The effects of poaching are predicted to cause a severe collapse of the population. Our results demonstrate the need for Moroccan authorities to be aware of the conservation issues of Barbary macaques and to stop tourists feeding them. This research work illustrates that the potential links between tourism and poaching should be taken into account regarding species conservation, even in protected areas. [ABSTRACT FROM AUTHOR]

Three related Aphidius parasitoid species share the same host, the grain aphid Sitobion avenae. Among this parasitoid community, Aphidius rhopalosiphi is the most abundant species in the field. Both the interspecific host discrimination of A. rhopalosiphi towards hosts parasitized by the two other species (i.e. A. avenae and A. ervi) and the interspecific host discrimination of the two other species towards hosts parasitized by A. rhopalosiphi were studied here. Results showed that females of A. rhopalosiphi and A. avenae both discriminated between unparasitized hosts and hosts parasitized by the other species. This discrimination occurred only after ovipositor insertion, suggesting the perception of an internal marker of parasitism. Likewise, females of A. rhopalosiphi and A. ervi were able to discriminate between unparasitized hosts and hosts parasitized by the other species. However, in this combination of species, recognition of parasitized hosts occurred before ovipositor insertion, through an antennal perception, suggesting the presence an external cue indicating parasitism. Hence, interspecific host discrimination in the three Aphidius species is based on internal or external cues, which are used either alone or together. Our results showed that the cues used for interspecific host discrimination depend on the specific identity of the interaction. These differences seemed strongly linked to the way the different species respond to defensive behaviours of their aphid hosts. Results are discussed in the context of optimal foraging and possible consequences for community structure. [ABSTRACT FROM AUTHOR]

Female philopatry characterizes many mammal populations subdivided into social groups. Fission of these social groups is a relatively discrete event in the life of groups or of individuals, leading to the distribution of females among several newly formed groups. Fission is an important event because it can be a way for females to disperse. Group fissions have rarely been observed and their modalities generally remain poorly known, the best-documented species being primates. Most group fissions occur along lines of maternal relatedness, but the death of a matriarch may disrupt the cohesion within a matriline, inducing separation of sisters, accompanied by their descendants, when a group splits. Our model shows that the numbers and sizes of matrilines within groups depend on the precise demographic parameters and age structure of a population and not only on its rate of increase. For comparable population-growth periods, high survival rates of adult females induce an increase in the sizes of matrilines, whereas high survival rates of immature individuals induce an increase in the numbers of matrilines. Following fission, groups of a given size included, in the first case, only a few large matrilines, whereas in the second case, they consisted mainly of many small matrilines. The present study constitutes a preliminary stage, before modelling consequences of demographic structure of groups or populations on their genetic structure. [ABSTRACT FROM AUTHOR]

Summary1. A detailed population dynamics model was devised to provide a tool for integrated pest management against the cereal aphid Sitobion avenae on winter wheat. 2. This model allowed investigation of the relative impact of different natural enemies on aphid population dynamics. 3. The output of the model was compared with a set of data collected in the western part of France from 1976 to 1986. 4. Fungal diseases accounted for 75% of the reduction in peak aphid density and were the key factor acting on aphid dynamics in this region. 5. This study highlights the importance of detailed population dynamics modelling of keystone species, like aphids, for elucidation of the relations between the keystone species and other species associated in the ecosystem. [ABSTRACT FROM AUTHOR]

Summary 1. Host discrimination by Aphidius rhopalosiphi (De Stefani Perez) (Hymenoptera: Braconidae) was first studied on the grain aphid Sitobion avenae (Fabricius) (Homoptera: Aphididae). Females tended to avoid oviposition in hosts parasitised 3 h earlier. No evidence of host discrimination ability on freshly parasitised hosts was suggested, however, and ovipositional experience had no effect on host discrimination. 2. The effects of host discrimination ability on the exploitation strategy of patches containing different proportions of unparasitised hosts and hosts parasitised for 3 h were studied. Females spent less time on patches with a higher proportion of parasitised hosts, reflecting the females' ability to perceive the potential profitability of the patch. This ability may be based on the nature of the hosts encountered (unparasitised or parasitised). 3. Incomplete exploitation of unparasitised hosts was also observed. It seems that this partial exploitation is related to the inability of A. rhopalosiphi to recognise freshly parasitised hosts. As a female may experience a risk of self-superparasitism during patch depletion, this could promote early departure from incompletely exploited patches. 4. The effect of previous experience on the patch exploitation strategy was also assessed. Females were tested twice on two patches of the same quality. Results suggested that the experience acquired during a previous visit led the females to leave the patch sooner and to lay fewer eggs in parasitised hosts. 5. Patch exploitation strategy may therefore be the result of different factors such as host discrimination and experience. The evolutionary consequences of the results are discussed. [ABSTRACT FROM AUTHOR]

Studies the evolution of breeding system variation within French populations of the aphid Sitobion avenae. How the present analysis combined ecological and genetic investigations into the spatial distribution of variation in reproductive mode; Results of analysis suggesting strong geographical partitioning of breeding systems, with obligate asexuals mostly restricted to the south of France, while lineages producing sexual forms were more common in the north; Data indicating that selection is important in structuring reproductive systems and genetic variation in French S. avenae; Examination of the associations between genotypic and phenotypic variables, enabling the identification of alleles correlated with life-history traits.

A collection of 87 ancient wheat genotypes, 67 Triticum monococcum, 13 Triticum boeoticum, seven Triticumn urartu and one cultivar of the modern wheat Triticum aestivum (variety `Arminda') were evaluated for resistance to the cereal aphid Sitobion avenae, the main damaging aphid pest on winter wheat in Europe. The intrinsic rate of natural increase (r[subm]), which is regarded as a good estimate of the fitness of an aphid population, was used as an indicator for the level of plant resistance. Differentiation of the 88 plant genotypes into four distinct groups was achieved with a cluster analysis of the r[subm] values. The modern wheat 'Arininda' was more susceptible than any of the ancient wheat genotypes tested (r[subm] = 0.24, i.e. the aphid population doubled every 2.6 days). A second group of 19 plants ranged from relatively susceptible to moderately resistant (0.17

Examines the effect of climate on the proportion of males in the autumn flight of aphid Rhopalosiphum padi in Great Britain. Reproduction of anholocycly; Composition of the autumn flights of cereal pest aphid; Factors affecting the geographical distribution of males.

The composition of autumn flights of a cereal pest aphid, Rhopalosiphum padi, was studied in relation to climate. At 10 sites in France and at Rothamsted and Starcross (UK), evidence was sought for a relationship between winter temperature and the proportion of males. By calculating Goldwin's correlogram, significant correlations were detected between cold periods in the early winter and the proportions of males at the five mildest sites, suggesting an effect of temperature on the balance between holocyclic and non-holocyclic clones. The five sites where no significant correlations were detected are generally cold in winter, and are likely to be largely dominated by holocyclic clones. The temperature in late summer/early autumn may also have an effect on the proportion of males. [ABSTRACT FROM AUTHOR]

The stylet penetration activities of Sitobion avenae F. were followed with an electronic method (DC-EPG) on resistant and susceptible wheat genotypes. Discriminant analysis was therefore applied to data evaluated on each electrical penetration graphs obtained (EPGs). The variables which mostly explained the resistance-susceptibility status of the wheat genotypes appeared to be related to the ingestion sap event (as represented by pattern E2), either to the time preceding first occurrence of a sap ingestion event or to the total time spent by the aphid ingesting sap from the sieve elements of the phloem. On the basis of their stylet penetration activities, individuals were separated into three blocks. The first one was made up the individuals tested on susceptible or slightly resistant wheat ('susceptible block'). The second one contained the individuals tested on two resistant genotypes ('resistant block l') and the third one regrouped the individuals tested on another resistant genotype ('resistant block 2'). These results are discussed in relation to the possible mechanisms of wheat resistance to S. avenae. [ABSTRACT FROM AUTHOR]

In order to establish whether commercial hybrid seed production between petalous and apetalous rapeseed lines could be developed through insect cross-pollination, observations were made to compare the foraging behaviour of honeybees on both flower types with regard to their attractiveness. Number of flowers/m² and nectar volumes, considered as important attractive factors, did not differ between the two lines but nectar sugar composition was slightly different. Honeybee density was significantly higher on the apetalous line when their foraging activity was rather high. Honeybees showed a considerable constancy to each flower type. Passages between both types were not very frequent. Nectar foraging behaviour, observed under cages, differed with the floral morphology. On the petalous flowers, honeybees visited the two inner nectaries by crawling over the anthers and the stigma, while on the apetalous ones they often inserted their tongues between the sepals, thus having less contact with the reproductive organs. From these results, the honeybee efficiency in cross-pollination between petalous and apetalous lines appears to be reduced. [ABSTRACT FROM AUTHOR]

Plant root systems play many key roles including nutrient and water uptake, interface with soil microorganisms and resistance to lodging. As for other crops, large and systematic studies of sugarcane root systems have always been hampered by the opaque and solid nature of the soil. In recent years, methods for efficient extraction of DNA from soil and for species-specific DNA amplification have been developed. Such tools could have potential to greatly improve root phenotyping and health diagnostic capability in sugarcane. In this paper, we present a fast, specific and efficient method for the quantification of sugarcane live root cells in soil samples. Previous studies were typically based on mass and length, so we established a calibration to convert root DNA quantity to live root mass. This diagnostic was validated on field samples and used to investigate the fate of the root system after harvest prior to regrowth of the ratoon crop. Two weeks after harvest, the sugarcane roots from the previous crop were still viable. This raises the question of the role that the root system of the harvested crop plays in the performance of the next crop and demonstrates how this test can be used to answer research questions. [ABSTRACT FROM AUTHOR]