LANDSCAPE CHANGES IN A LOWLAND IN BENIN: ECOLOGICAL IMPACT ON PESTS AND NATURAL ENEMIES.

Habitat management involving conservative biological control could be a good crop pest management option in poor African countries. A survey was conducted from August 2013 to July 2014 in a rainfed lowland region near Pélébina, northern Benin, in order to characterize spatiotemporal landscape changes and investigate their influence on the main crop pests and their associated natural enemies. The area was mapped mainly regarding crop fields and fallows. Visual observations were recorded and a database was compiled. Major landscape composition changes were noted between rainy and dry seasons, which affected the presence of both pests and natural enemies. Cereals (rice, maize and sorghum) and cotton were grown in the humid season, and then okra (Abelmoschus esculentus) was the dominant vegetable crop in dry season. These modifications impacted fallow abundance throughout the lowland. Different cotton (e.g. Helicoverpa armigera, Dysdercus sp., Zonocerus variegatus) or rice (e.g. Diopsis longicornis, D. apicalis) pests were observed during dry season in okra crops. Dry season surveys of Poaceae in two types of fallows ('humid', 'dry') revealed the presence of very few stem borers: only 0.04% of stems sampled were infested by stem borers, with a mean of 1.13 larvae per stem. Known cereal stem borer species such as Busseola fusco, Coniesta ignefusalis, Sesamia calamistis were not clearly identified among these larvae because of their diapausing stage and white color. Unexpected pollinators (Hymenoptera Apidae, genus Braunsapis, Ceratina and Xylocopa) and predators (Crabronidae, genus Dasyproctus) were found in the stems. Sweep-net collection of insects in humid fallows allowed us to describe for the first time in Benin seven Diopsidae species (23% of adults bearing Laboulbeniomycetes ectoparasitic fungi). Some of these species were captured in rice fields during rainy season. Parasitoids (adult Chalcidoidae and Ichneumonoidae) were observed during both seasons but their impact on stem borers was hard to determine, even during the rainy season, due to their low abundance and the difficulty of identification. Predators (Reduviidae, Odonata) were found mainly in humid fallows and rice fields. Regarding our observations, we suggest the presence of alternate host crops such as okra during the dry season for rainy season crop pests. Moreover, fallows also had a real ecological role as a habitat resource for many guilds of insects (pollinators, pests, predators). The management of these landscape components should be the focus of a long-term study with the aim of enhancing pest management of rainy season crop pests.

Can deuterium stable isotope values be used to assign the geographic origin of an auxiliary hoverfly in south-western France?

Deuterium δD isotopic analysis is increasingly being used to trace wildlife movement, and undoubtedly has much to offer in this respect, but questions still remain as to the feasibility and practicality of the method in ecology. Here we report our attempt to determine the geographic origin of an auxiliary hoverfly, Episyrphus balteatus, in south-western France. We used quantile regression to calculate the minimum separation distance, based on the International Atomic Energy Agency/World Meteorological Organization (IAEA/WMO) data, at which two insects could be said to originate from different latitudes with a given degree of confidence. We collected larvae in spring 2007 and 2009 to obtain the δD signal of indigenous hoverflies and we trapped adults during one complete year (from Dec. 2006 to Nov. 2007). The smallest separation distance calculated was about 1400 km in western Europe. Our results revealed greater variability in δD of adults in autumn than in spring. From this we infer an autumnal migration. Because of the presence of mountains and the Mediterranean Sea, the δD gradient in precipitation in western Europe is less clear than on the American continent, where it has been used successfully to infer geographical origins of animals under certain conditions. Despite the complications encountered in Europe, the minimum separation distance model proved a useful first step to obtain a first range of possible origins of E. balteatus and the application of the model to other arthropod species in Europe warrants investigation.

Demic expansions and human evolution.

Geographic expansions are caused by successful innovations, biological or cultural, that favor local growth and movement. They have had a powerful effect in determining the present patterns of human genetic geography. Modern human populations expanded rapidly across the Earth in the last 100,000 years. At the end of the Paleolithic (10,000 years ago) only a few islands and other areas were unoccupied. The number of inhabitants was then about one thousand times smaller than it is now. Population densities were low throughout the Paleolithic, and random genetic drift was therefore especially effective. Major genetic differences between living human groups must have evolved at that time. Population growths that began afterward, especially with the spread of agriculture, progressively reduced the drift in population and the resulting genetic differentiation. Genetic traces of the expansions that these growths determined are still recognizable.

Synthetic maps of human gene frequencies in Europeans.

Multivarate techniques can be used to condense the information for a large number of loci and alleles into one or a few synthetic variables. The geographic distribution of synthetic variables can be plotted by the same technique used in mapping the gene frequency of a single allele. Synthetic maps were constructed for Europe and the Near East, with the use of principal components to condense the information of 38 independent alleles from ten loci. The first principal component summarizes close to 30% of the total information and shows gradients. Maps thus constructed show clines in remarkable agreement with those expected on the basis of the spread of early farming in Europe, thus supporting the hypothesis that this spread was a demic spread rather than a cultural diffusion of farming technology.

Spruce colonization at treeline: where do those seeds come from?

At treeline, selection by harsh environmental conditions sets an upward limit to arboreal vegetation. Increasing temperatures and the decline of traditional animal raising have favoured an upward shift of treeline in the last decades. These circumstances create a unique opportunity to study the balance of the main forces (selection and gene flow) that drive tree migration. We conducted a parentage analysis sampling and genotyping with five microsatellite markers in all Norway spruce individuals (342 juveniles and 23 adults) found in a recently colonized treeline area (Paneveggio forest, Eastern Alps, Italy). Our goal was to evaluate local reproductive success versus gene flow from the outside. We were able to identify both parents among local adults for only 11.1% of the juveniles. In the gamete pool we sampled, two-thirds were not produced locally. Effective seed dispersal distance distribution was characterized by a peak far from the seed source (mean 344.66 m+/-191.02 s.d.). Reproductive success was skewed, with six local adults that generated almost two-thirds (62.4%) of juveniles with local parents. Our findings indicate that, although a few local adults seem to play an important role in the colonization process at treeline, large levels of gene flow from outside were maintained, suggesting that the potential advantages of local adults (such as local adaptation, proximity to the colonization area, phenological synchrony) did not prevent a large gamete immigration.

Using stable isotopes to trace origin and host plants of an African polyphagous pest and an European beneficial insect.

Crop protection against insect pests requires first a good knowledge of the biology and ecology of the different pest species and the associated beneficials, in particular the spatial distribution of the populations. But the movement of insect populations in the landscape remains often poorly known and in some cases does not make it possible to know the role of the various cultivated and wild habitats in the dynamics of pest and useful insects. Stable isotopes are a tool contributing to the knowledge of host plants (13carbon/12carbon) as well as geographical origin of insects (1hydrogen/2hydrogen). The analysis of stable isotopic ratios has been performed in south-western France on populations of the hoverfly Episyrphus balteatus, one of the most important predators of the cereal aphids in Europe and on West African populations of the bollworm Helicoverpa armigera, an important polyphagous pest attacking cotton and vegetables in the Old World. Methodology, preliminary results and perspectives given by stable isotopes are presented here.

The HLA-A,B gene frequencies in the world: migration or selection?

Multivariate methods make it possible to condense much of the information available for a large number of alleles into one or a few synthetic variables. The geographic distribution of synthetic variables can be analyzed and plotted by the same technique used in analyzing and mapping the gene frequency of a single allele. The information contained in 21 HLA-A and HLA-B alleles from 116 world populations is condensed in principal components and discriminant functions which describe the global variation of gene frequencies along longitudes and along latitudes. Most genetic variation is associated with longitude and shows a center of symmetry in Asia. Thus Asia, or some part of it, may have been the center, both geographically and historically, of late Pleistocene migrations. However, latitude also plays a significant role (perhaps 10% of the genetic variation). A remarkable symmetry of the latitude variation in opposite (north and south) hemispheres suggest that climatic factors exercise selective pressure for certain HLA alleles. More specifically A1, A3, B7, B8, and B27 show about equally high correlation coefficients (between 0.45 and 0.55) with distance from equator. This result supports the idea that the well-known linkage disequilibria between A1 and B8, A3 and B7 are probably kept by selective pressure.

Reduction of GH response to the GABA-B agonist baclofen in patients with major depression.

In order to establish whether alterations in the GABAergic control of GH secretion occur in male patients with major depression, the GH response to the GABAergic-B agonist baclofen (10 mg PO at 0830h) or to placebo was tested in 9 depressed men and in 10 age- and weight-matched male normal controls. The basal concentrations of GH were significantly lower in the depressed patients (0.87 +/- 0.69 ng/ml) than in the normal controls (1.57 +/- 0.33 ng/ml) (p = 0.011) and were not modified by the administration of placebo. The administration of baclofen induced a striking, significant increase in GH concentrations in the normal controls (mean peak at 90 min = 6.4 +/- 1.5 ng/ml). In contrast, a slight, nonsignificant GH increase occurred in the depressed patients after baclofen (mean peak at 90 min = 1.57 +/- 1.45 ng/ml). The GH response was significantly lower in the depressed than in the control subjects (p less than 0.001). These data indicate the presence of reduced GABAergic control of GH secretion in male depressed patients.

Biochemical characterization of the cotton bollworm Helicoverpa armigera resistance to pyrethroids in Burkina Faso.

The bollworm Helicoverpa armigera is cotton plant main pest in most parts of the world. The mechanisms of the resistance of the bollworm to the pyrethroid deltamethrin were studied by comparing field strains to the reference and susceptible strain (BK77). Resistance to deltamethrin was studied using bio-assays. Results showed that the field collected strains had susceptibility 11 to 43 fold lower than that of the susceptible standard strain BK77. Activities of two types of enzymes i.e., oxidases and Glutathione-S-Transferases (GST) were significantly higher in field strains, whereas esterase activities were lower compared to that of standard strain. The increase of oxidases and GST activities and the decrease of esterase activity are at least in part, responsible for the development of resistance of H. armigera to pyrethroids.

Segregation analysis of random amplified polymorphic DNA (RAPD) markers in Picea abies Karst.

The reliability of arbitrarily primed amplification products was tested. The segregation analysis of 266 amplification products obtained using 17 different 10-mer oligonucleotides in 34 megagametophytes from a single tree of Picea abies was carried out. Fifty-four out of the 165 variable bands fit the 1:1 segregation ratio expected for Mendelian traits. The segregation ratio of a subset of six RAPD markers in five other individuals from the same population confirmed their genetic nature. Our results strengthen the evidence previously reported that RAPDs markers can be considered Mendelian traits useful in the detection of genetic variability among both different individuals and populations.

Intraindividual and intraspecies variability of ITS1 sequences in the ancient asexual Darwinula stevensoni (Crustacea: Ostracoda).

The lack of variability in ITS regions within individuals and within species has been explained as the result of concerted evolution. In fact, many examples of intraindividual variation in the ITS regions have been reported. Here we report evidence of within-individual variation of the ITS1 region in the obligate parthenogenetic species Darwinula stevensoni. We analysed 46 clones obtained from 12 individuals of D. stevensoni, from three Italian sites and one site in Luxembourg. Seven nucleotides out of 366 were variable. Most variability (80%) was found among clones within individuals, and the remainder of the variability was observed among individuals. No difference was found among populations or between habitats. The low intraspecific variability and the observation of recombinant molecules are evaluated in light of the relevant literature. The high percentage of variation within individuals and the occurrence of recombination without meiosis are discussed by considering the ancient asexual "status" of the species.

Synthetic gene frequency maps of man and selective effects of climate.

The world distribution of 39 independent gene frequencies in human populations is analyzed by multivariate techniques and synthetic geographic maps. Most genetic variation is associated with longitude, with South Asia showing a tendency to be central. Also latitude and, more particularly, distance from the equator play a significant role in a way that suggests that climatic factors exercise selective pressures, especially for certain genes.

A model and program for study of a tolerance curve: application to lactose absorption tests.

A method has been devised for the analysis of tolerance curves, and tested on data collected for the diagnosis of lactose malabsorption with lactose tolerance tests. Two different models were fitted to over 100 experimental curves; the need to allow small changes over time in the glucose baseline level became evident, indicating that a model allowing a time trend is preferable. The results are briefly discussed and the biological significance of the quantities estimated by the method is discussed.

Reconstruction of human evolution: bringing together genetic, archaeological, and linguistic data.

The genetic information for this work came from a very large collection of gene frequencies for "classical" (non-DNA) polymorphisms of the world aborigines. The data were grouped in 42 populations studied for 120 alleles. The reconstruction of human evolutionary history thus generated was checked with statistical techniques such as "boot-strapping". It changes some earlier conclusions and is in agreement with more recent ones, including published and unpublished DNA-marker results. The first split in the phylogenetic tree separates Africans from non-Africans, and the second separates two major clusters, one corresponding to Caucasoids, East Asians, Arctic populations, and American natives, and the other to Southeast Asians (mainland and insular), Pacific islanders, and New Guineans and Australians. Average genetic distances between the most important clusters are proportional to archaeological separation times. Linguistic families correspond to groups of populations with very few, easily understood overlaps, and their origin can be given a time frame. Linguistic superfamilies show remarkable correspondence with the two major clusters, indicating considerable parallelism between genetic and linguistic evolution. The latest step in language development may have been an important factor determining the rapid expansion that followed the appearance of modern humans and the demise of Neanderthals.

A method to estimate acetylcholinesterase-active sites and turnover in insects.

Acetylcholinesterase is the primary target of organophosphorous and carbamate insecticides. Quantitative changes in acetylcholinesterase are suspected to confer resistance to these insecticides, but a method to estimate the amount in insect is not available. A method using irreversible inhibitors has been developed. Among the irreversible inhibitors tested, 7-(methylethoxyphosphinyloxy)-1-methylquinolinium iodide, chlorpyrifos-ethyl-oxon, and coumaphos-oxon were found to be sufficiently potent and specific.

Uralic genes in Europe.

We have analysed data of three European populations speaking non-Indoeuropean languages: Hungarians, Lapps, and Finns. Principal coordinate analysis shows that Lapps are almost exactly intermediate between people located geographically near the Ural mountains and speaking Uralic languages, and central and northern Europeans. Hungarians and Finns are definitely closer to Europeans. An analysis of genetic admixture between Uralic and European ancestors shows that Lapps are slightly more than 50% European, Hungarians are 87% European, and Finns are 90% European. There is basic agreement between these conclusions and historical data on Hungary. Less is known about Finns and very little about Lapps.

Genetics and the origin of European languages.

A new set of European genetic data has been analyzed to dissect independent patterns of geographic variation. The most important cause of European genetic variation has been confirmed to correspond to the migration of Neolithic farmers from the area of origin of agriculture in the Middle East. The next most important component of genetic variation is apparently associated with a north-south gradient possibly due to adaptation to cold climates but also to the differentiation of the Uralic and the Indo-European language-speaking people; however, the relevant correlations are not significantly different from zero after elimination of the spatial autocorrelation. The third component is highly correlated with the infiltration of the Yamna ("Kurgan") people, nomadic pastoralists who domesticated the horse and who have been claimed to have spread Indo-European languages to Europe; this association, which is statistically significant even when taking spatial autocorrelations into account, does not completely exclude the hypothesis of Indo-European as the language of Neolithic farmers. It is possible that both expansions were responsible for the spread of different subfamilies of Indo-European languages, but our genetic data cannot resolve their relative importance.