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International audience; Ambrosia trifida L. (giant ragweed, Asteraceae) is native to the North American continent and was introduced into Europe and Asia at the end of the 19th century. In its native range, this tall annual species is common in riparian and ruderal habitats and is also a major weed in annual cropping systems. For nearly a century, A. trifida has also been of great concern in the U.S. for its highly allergenic pollen, necessitating targeted control measures to reduce its impact on human populations. Based on the distribution of A. trifida in North America and in its introduced range, riparian systems in the rest of the world may be particularly at risk to invasion, with potential negative consequences for their biodiversity. Currently, A. trifida has invaded Asia more widely than Europe, likely due to the more favourable local conditions in Asia. Throughout its introduced range, A. trifida is host to a limited number of invertebrates and pathogens and only a few biological agents are available for its control. The main impacts of A. trifida at a global level are on crop yield and human health, resulting in significant socio-economic impacts. The success of A. trifida invasion in areas in which it has been introduced is still unclear, but climate change may increase climate suitability, increasing the potential for A. trifida to spread. While effective management in cultivated fields seems potentially possible, the development and control of A. trifida in natural riparian habitats is of great concern due to the difficulty of management in these areas.

Fastq paired reads for analyzed samples are available as a NCBI Sequence Read Archive (ID#PRJNA606284). Custom script to detect cross-contamination is available from https://github.com/DNAdiversity/UCE-Cross-Contamination-Check.Datasets (morphological matrix, concatenated UCEs) and trees have been uploaded on Zenodo (https://doi.org/10.5281/zenodo.3666638).; International audience; Recent technical advances combined with novel computational approaches have promised the acceleration of our understanding of the tree of life. However, when it comes to hyperdiverse and poorly known groups of invertebrates, studies are still scarce. As published phylogenies will be rarely challenged by future taxonomists, careful attention must be paid to potential analytical bias. We present the first molecular phylogenetic hypothesis for the family Chalcididae, a group of parasitoid wasps, with a representative sampling (144 ingroups and seven outgroups) that covers all described subfamilies and tribes, and 82% of the known genera. Analyses of 538 Ultra-Conserved Elements (UCEs) with supermatrix (RAxML and IQTREE) and gene tree reconciliation approaches (ASTRAL, ASTRID) resulted in highly supported topologies in overall agreement with morphology but reveal conflicting topologies for some of the deepest nodes. To resolve these conflicts, we explored the phylogenetic tree space with clustering and gene genealogy interrogation methods, analyzed marker and taxon properties that could bias inferences and performed a thorough morphological analysis (130 characters encoded for 40 taxa representative of the diversity). This joint analysis reveals that UCEs enable attainment of resolution between ancestry and convergent/divergent evolution when morphology is not informative enough, but also shows that a systematic exploration of bias with different analytical methods and a careful analysis of morphological features is required to prevent publication of artifactual results. We highlight a GC content bias for maximum-likelihood approaches, an artifactual mid-point rooting of the ASTRAL tree and a deleterious effect of high percentage of missing data (>85% missing UCEs) on gene tree reconciliation methods. Based on the results we propose a new classification of the family into eight subfamilies and ten tribes that lay the foundation for future studies on the evolutionary history of Chalcididae.

Despite their ecological and evolutionary importance as key components of tropical ecosystems, the phylogeny of fig trees is still unresolved. We use restriction-site-associated DNA (RAD) sequencing (ca420kb) and 102 morphological characters to elucidate the relationships between 70 species ofFicusrepresenting all known subgenera and sections and five outgroups. We compare morphological and molecular results to highlight discrepancies and reveal possible inference bias. We analyse marker and taxon properties that may bias molecular inferences, with existing softwares and a new approach based on iterative principal component analysis to reduce variance between clusters of samples. For the first time, with both molecular and morphological data, we recover a monophyletic subgenusUrostigmaand a clade with all gynodioecious fig trees. However, our analyses show that it is not possible to homogenize evolutionary rates and GC content for all taxa prior to phylogenetic inference and that four competing positions for the root of the molecular tree are possible. The placement of the long-branched sectionPharmacosyceaas sister to all other fig trees is not supported by morphological data and considered as a result of a long branch attraction artefact to the outgroups. Regarding morphological features and indirect evidence from the pollinator tree of life, the topology that divides the genusFicusinto monoeciousversusgynodioecious species appears most likely. Active pollination is inferred as the ancestral state for all topologies, ambiguity remains for ancestral breeding system including for the favored topology, and it appears most likely that the ancestor of fig trees was a freestanding tree. Increasing sampling may improve results and would be at least as relevant as maximizing the number of sequenced regions given the strong heterogeneity in evolutionary rates, and to a lesser extent, base composition among species. Despite morphological plasticity and frequent homoplasy of multiple characters, we advocate giving a central role to morphology in our understanding of the evolution ofFicus, especially as it can help detect insidious systematic errors that tend to become more pronounced with larger molecular data sets.

International audience; The bark beetle genus Dendroctonus contains some of the most economically important pests of conifers worldwide. Despite many attempts, there is no agreement today on the phylogenetic relationships within the genus, which limits our understanding of its evolutionary history. Here, using restriction-site associated DNA (RAD) markers from 70 specimens representing 17 species (85% of the known diversity) we inferred the phylogeny of the genus, its time of origin and biogeographic history, as well as the evolution of key ecological traits (host plants, larval behavior and adults’ attack strategies). For all combinations of tested parameters (from 6,444 to 23,570 RAD tags analysed), the same, fully resolved topology was inferred. Our analyses suggest that the most recent common ancestor (mrca) of all extant Dendroctonus species was widely distributed across eastern Palearctic and western Nearctic during the early Miocene, from where species dispersed to other Holarctic regions. A first main inter-continental vicariance event occurred during early Miocene isolating the ancestors of D. armandi in the Palearctic, which was followed by the radiation of the main Dendroctonus lineages in North America. During the Late Miocene, the ancestor of the ‘rufipennis’ species group colonized north-east Palearctic regions from western North America, which was followed by a second main inter-continental vicariance event isolating Pleistocene populations in Asia (D. micans) and western North America (D. murrayanae and D. punctatus). The present study supports previous hypotheses explaining intercontinental range disjunctions across the Northern Hemisphere by the fragmentation of a continuous distribution due to climatic cooling, host range fragmentation and geological changes during the late Cenozoic. The reconstruction of ancestral ecological traits indicates that the mrca bored individual galleries and mass attacked the boles of pines. The gregarious feeding behavior of the larvae as well as the individual attack of the base of trees have apparently independently evolved twice in North America (in the ‘rufipennis’ and the ’valens’ species groups), which suggests a higher adaptive potential than previously thought and may be of interest for plant protection and biodiversity conservation in a rapidly changing world.

The bacterium Xylella fastidiosa (Xf) is a plant endophyte native to the Americas that causes worldwide concern. Xf has been recently detected in several regions outside its natural range including Europe. In that context, accurate estimates of its response to climate change are required to design cost-efficient and environment-friendly control strategies. In the present study, we collected data documenting the native and invaded ranges of the three main subspecies of Xf: fastidiosa, pauca and multiplex, as well as two strains of Xf subsp. multiplex recently detected in southern France (ST6 and ST7). We fitted bioclimatic species distribution models (SDMs) to forecast their potential geographic range and impact in Europe under current and future climate conditions. According to model predictions, the geographical range of Xf as presently reported in Europe is small compared to the large extent of suitable areas. The European regions most threatened by Xf encompass the Mediterranean coastal areas of Spain, Greece, Italy and France, the Atlantic coastal areas of France, Portugal and Spain as well as the south-western regions of Spain and lowlands in southern Italy. Potential distribution of the different subspecies / strains are contrasted but all are predicted to increase by 2050, which could threaten several of the most economically important wine-, olive- and fruit-producing regions of Europe, warranting the design of control strategies. Bioclimatic models also predict that the subspecies multiplex might represent a threat to most of Europe under current and future climate conditions. These results may serve as a basis for future design of a spatially informed European-scale integrated management strategy, including early detection surveys in plants and insect vectors, quarantine measures as well as agricultural practices.

Key message[br/] Despite variable dynamics of genetic diversification at the different altitudinal levels, strong gene flow tends to standardize larch genetic diversity: the larch forest distributed along the altitudinal gradient can be regarded as a single population.[br/] [br/] Context[br/] While in forest tree species many studies focus on the structure of the genetic diversity at the natural range and at the forest stand levels, few studies have worked at intermediate levels like the landscape level.[br/] [br/] Aims[br/] We tried to determine to what degree altitude variation can affect the genetic diversity and the local structure of the genetic diversity of European larch (Larix decidua Miller) at the landscape level.[br/] [br/] Methods[br/] Using microsatellite markers, we determined the between- and within-plot genetic structure and the spatial genetic structure (SGS) of four altitudinal plots distributed between 1,350 and 2,300 m a.s.l. in a European larch forest located in the French Alps.[br/] [br/] Results[br/] A homogenous neutral genetic structure was detected along this gradient. The intensity of the SGS was found to be stronger at 2,300 m and decreased at the 2,000-m plot. It was low or non-existent at the 1,700- and 1,350-m altitudinal levels.[br/] [br/] Conclusion[br/] Our results suggest that the genetic structure observed at the landscape level in this European larch forest was only slightly affected by climatic variation, human activities, or historical events. However, the variation of intensity of the SGS within the altitudinal plots indicates the existence of variable genetic dynamics, despite the globally uniform genetic structure along the altitudinal gradient.

We sampled ca 2500 specimens of Philaenus spumarius throughout Corsica without a priori on the presence of symptoms on plants. We screened 448 specimens for the presence of Xylella fastidiosa (Xf) using qPCR and a custom nested PCR. qPCR appeared versatile and under-estimated the prevalence of Xf. Nested PCR showed that Xf was present in all populations. Molecular results were validated by prediction on the distribution of Xf made from tests conducted on plants, which shows the pertinence of using vectors in risk assessment studies. Xf was detected in tenerals and adults. Thus, P. spumarius could acquire Xf from its host plant, mostly Cistus monspeliensis in Corsica, which may act as reservoir for the next season. This contrasts with other observations and suggests that management strategies may have to be adapted on a case-by-case basis. At least two genetic entities and several variants of Xf not yet identified on plants were present in the insects, which suggests ancient introductions of Xf and a probable underestimation of the current diversity of the strains present in Corsica. Interestingly 6% of the specimens carried two subspecies. Studies are wanted to better characterize the strains present in Corsica and know how the disease was introduced, spread and why no sign of a potential epidemic was detected earlier. This study shows that, when sensitive enough methods are implemented, insects can be used to predict and better assess the exact distribution of Xf. Insects are indeed easy to collect, Xf multiply only in their foregut and does not become circulative, which facilitates its detection., This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement N. 727987 "Xylella fastidiosa Active Containment Through a multidisciplinary-Oriented Research Strategy XF-ACTORS"

Various species of forest trees are commonly used for ornamental purposes and are therefore frequently found in non-forest ecosystems. These trees constitute a significant component of the trees outside forests (TOF). Although increasingly recognized as prominent feature of agricultural lands and built-up areas, not much is known, however, about TOF since they are generally absent from forest inventories. In the present study, we focus on the coniferous tree species that constitute potential hosts for a forest defoliator, the pine processionary moth Thaumetopoea pityocampa Den. & Schiff. (Lepidoptera, Notodontidae). We carried out an exhaustive inventory of all pines (Pinus spp.), cedars (Cedrus spp.) and Douglas-fir (Pseudotsuga menziesii) in a 22 × 22 km study window located in the open-field region of Beauce in the centre of France. We recorded a total of 3834 individuals or small groups host trees corresponding a density of 7.9 occurrences per 100 ha. We provide the spatial coordinates of the points without differentiation between tree species.

The longevity of a generalist (Ooencyrtus pityocampae) and a specialist (Baryscapus servadeii) egg parasitoid of the pine processionary moth (Thaumetopoea pityocampa) was compared under laboratory feeding conditions including water and honeydew from aphid species growing on maritime pine (Pinus pinaster) or pedunculate oak (Quercus robur). The longevity of both parasitoid species increased when specimens were fed with honeydew. This increase was larger for the generalist (3.7, 32.0 and 38.0 days) than for the specialist (3.0, 23.3 and 21.5 days) parasitoid species when fed with water, oak and pine aphid honeydew respectively. The phenology of the specialist species B. servadeii is well-adapted with its host availability with or without food supply. The generalist species O. pityocampae could overlap its host emergence curve during 14.0–20.0 days when fed with oak and pine aphid honeydew respectively, vs. no overlap when no supplementary food was provided. Analysis of honeydew composition indicated that sugars and amino acids may have distinct effects on parasitoid longevity. J. Appl. Entomol.

A plausible case of allochronic differentiation, where barrier to gene flow is primarily attributable to a phenological shift, was recently discovered in Portugal for the pine processionary moth Thaumetopoea pityocampa. Previous results suggested that the observed ‘summer population’ (SP) originated from the sympatric winter population (WP). Our objectives were to finely analyse these patterns and test their stability in time, through field monitoring and genetic analyses of larvae and adults across different years. Reproductive activity never overlapped between SP and WP. Microsatellites showed a clear differentiation of the SP, consistent with a strong reduction in gene flow owing to the phenological shift. Assignment tests suggested that some individuals shift from the SP to the WP phenology, causing some hybridization. We discuss these patterns and their maintenance over time. This could be a first stage of allochronic speciation, and SP should be considered as a distinct phenological race.

Landscape composition and physiognomy affect community structure and species distribution across space and time. The pine processionary moth (PPM) (Thaumetopoea pityocampa Den. & Schiff., Lepidoptera, Notodontidae) is a common pine defoliator throughout southern Europe and Mediterranean countries. We surveyed the spatiotemporal distribution of the PPM in a pine plantation forest in southwestern France and used the density of the winter nests as a proxy for population density. The study spanned 4 years (2005–2008) and showed a high temporal variability in nest density. We found a strong edge effect with nest densities at stand edges more than twice as large as within-stand densities. At the landscape scale, the spatial distribution of the moth exhibited a significant spatial autocorrelation in 3 out of 4 years of our study. The spatial scales of the autocorrelation ranged from ca. 2 km to more than 22 km. We found a positive correlation between spatial distributions corresponding to certain sampling years, but the relationship was not systematic. Landscape configuration appeared to be an important driver of the PPM spatial pattern. Bivariate Moran’s I correlograms showed that patch richness density as well as the percentage of local landscape covered by various land uses were correlated with population density. The study showed that accounting for landscape characteristics may be important in order to understand forest insect pest distribution, even in cases where the host species is abundant and homogeneously distributed throughout the study area, e.g., pure plantation forests.

International audience; Bark beetles are notorious pests of natural and planted forests causing extensive damage. These insects depend on dead or weakened trees but can switch to healthy trees during an outbreak as mass-attacks allow the beetle to overwhelm tree defences. Climatic events like windstorms are known to favour bark beetle outbreaks because they create a large number of breeding sites, i.e., weakened trees and for this reason, windthrown timber is generally preventively harvested and removed. In December 1999, the southwest of France was struck by a devastating windstorm that felled more that 27 million m3of timber. This event offered the opportunity to study large-scale spatial pattern of trees attacked by the bark beetle Ips sexdentatus and its relationship with the spatial location of pine logs that were temporally stored in piles along stand edges during the post-storm process of fallen tree removal. The study was undertaken in a pure maritime pine forest of 1300 ha in 2001 and 2002. We developed a landscape approach based on a GIS and a complete inventory of attacked trees. During this study more than 70% of the investigated stands had at least one tree attacked by I. sexdentatus. Spatial aggregation prevailed in stands with n≥15 attacked trees. Patches of attacked trees were identified using a kernel estimation procedure coupled with randomization tests. Attacked trees formed patches of 500–700 m2 on average which displayed a clumped spatial distribution. Log piles stemming from the sanitation removals were mainly distributed along the large access roads and showed an aggregated spatial pattern as well. The spatial relationship between patches of attacked trees and log pile storage areas was analyzed by means of the Ripley’s statistic that revealed a strong association at the scale of the studied forest. Our results indicated that bark beetle attacks were facilitated in the vicinity of areas where pine logs were stored. The spatial extent of this relationship was >1000 m. Similar results were obtained in 2001 and 2002 despite differences in the number and spatial distribution of attacked trees. The presence of a strong “facilitation effect” suggests that log piles should be removed quickly in order to prevent outbreaks of bark beetles.

The spatio-temporal structure of an earthworm community was assessed in a tropical Colombian pasture and compared with the patterns of soil heterogeneity. Earthworms were sampled at six dates during a period of one year, while soil properties were assessed at a single date at the end of this period. Sample design was spatially explicit and consisted in a regular grid of 5 m mesh. At each date, 120 samples were taken for earthworm evaluations, while the single soil sampling consisted in 60 points. Multivariate and geostatistical analyses were performed to describe the spatial structure of collected data. Mantel and partial Mantel's tests were used to assess the links between the spatio-temporal patterns of earthworm distribution and soil heterogeneity. The results clearly demonstrated the existence of structured spatial patterns in the earthworm community which were stable in time, at least at the temporal scale concerned by the study period. It mostly corresponded to an alternation of patches where particular species assemblages dominated. The ecological significance of these assemblages is discussed. Soil properties also displayed a significant spatial organisation. Only a small part of the spatio-temporal structures of earthworm distribution was correlated with soil properties. Small species were more abundant in patches where soil was more compact, while large species were associated with high root biomass and total C levels. The question whether earthworm spatio-temporal distribution induces similar patterns in soil properties or the contrary occurs is discussed. Our results suggest that earthworm community organisation mostly corresponds to a non-equilibrium system where mobile earthworm populations influence soil properties. The overall effect of earthworm community on soil is difficult to assess due to the predominance of factors that preferentially express themselves at large scales in the ecological hierarchy.

The dataset supplied in this article provides the spatial location and the species composition of urban trees belonging to three coniferous genera (Pinus, Cedrus and Pseudotsuga) inventoried in 5 districts of the city of Orléans (France). A total of 9321 trees were georeferenced. The most abundant species was the black pine Pinus nigra for which a total of 2420 trees were observed. Other common species were the scots pine P. sylvestris, the Douglas-fir Pseudotsuga menziesii and different species of the genus Cedrus. The data supplied in this article are related to “A citywide survey of the pine processionary moth Thaumetopoea pityocampa spatial distribution in Orléans (France)” by J.-P. Rossi, V. Imbault, T. Lamant, J. Rousselet,) [3].

acceptée; Despite evidence that conspecific lineages may display different climatic tolerances, most invasion risk assessment tools are calibrated without considering phylogeographic information. This study aims to investigate the existence of intraspecific niche divergence within a group of insect pests and to explore how the inclusion of phylogeographic information into species distribution models may alter the estimation of the potential distribution of a species. We studied North American bark beetles belonging to the genus Dendroctonus, a group of pests of conifers that are listed as quarantine species in numerous countries. Most Dendroctonus species exhibit strong genetic divergence that appears to be geographically structured and shaped by historical events and biotic factors. We modeled all lineage distributions within five species, using MaxEnt and Boosted Regression Trees, and compared the results with the models fitted at the species scale. Multivariate analysis and niche similarity and equivalency tests were additionally performed to investigate the existence and magnitude of climatic niche divergence between conspecific lineages. We also tested the ability of lineage-based models to predict the region invaded by D. valens in China. Conspecific lineages showed a climatic niche more similar than expected by chance, but displayed different climatic envelopes in their native range and, consequently, different estimates of potential distributions. We also observed that classical models calibrated using the entire range of the species could potentially under-or overestimate the potential range of the species when compared to a global prediction built by aggregating lineage-based projections. This study showed that the invasive phylogeographic lineage of D. valens has invaded regions characterized by climatic conditions highly similar to those encountered in its native range suggesting that preadaptations to environment might have played a role in this invasion. This study highlights how our perception of the invasion risk of pests may be altered when integrating phylogeographic information.

There is a growing recognition that urban trees provide various valuable benefits and services such as enhanced human wellbeing. However, they also have a cost in terms of public health either directly (allergies) or by harboring species representing health risk for humans. This paper focuses on such a forest insect species, the pine processionary moth Thaumetopoea pityocampa. Its caterpillars develop gregariously during winter in a conspicuous silk nest in coniferous hosts. When disturbed, the larvae release urticating hairs that cause human or animal serious health problems. The purpose of our survey was to (1) inventory all individual trees belonging to potential host species and estimate the density of T. pityocampa (2) assess the spatial pattern of the insect population at the city scale. We conducted an exhaustive inventory of potential coniferous host trees in five municipalities (ca. 5000 ha) in the north of Orleans, France. Each tree was identified, geo-referenced and the number of moth nests it hosted was counted. A total of 9321 urban trees representing 11 coniferous taxonomic units were investigated. The distribution of T. pityocampa exhibited a marked spatial structure citywide. Geostatistics allowed to draw risk maps revealing strong patchiness. We provide the first estimate of T. pityocampa host tree preference in an urban context and found that Pinus nigra, P. pinaster and P. sylvestris were the most attacked trees. We also report numerous cases of T. pityocampa occurrence on the exotic ornamental Himalayan cedar Cedrus deodara. The management implications of our findings are two-fold: (1) risk maps constitute a useful framework for communication and public information, and can help developing control strategies; (2) some species frequently used for ornamental purposes are poor quality hosts regarding T. pityocampa and should therefore be preferred in public place usually frequented by vulnerable people (schools, nurseries, hospitals). (C) 2016 Published by Elsevier GmbH.

Background The impact of earthworms on both soil physical properties and soil organic matter dynamics has been well documented (Lavelle and Spain 2001). There is a wealth of literature dedicated to the biological mechanisms at work or to empirical approaches based on field data. Assessing the functional role of a species or community implies establishing both time and space scales at which it is effectively the primary determinant of the process(es) at hand. In that context, space-time data analyses are powerful tools to process community data collected on numerous occasions but are, however, not widely disseminated in the community of ecologists. Although computer resources are available, one difficulty is that ad hoc field data are not always easily available which hinders the percolation of the methods. New information We provide the results of a 5 dates survey of earthworm community in a grass savanna of Lamto (Ivory Coast) conducted between 1995 and 1997. At each sampling date, earthworm community was assessed by hand-sorting a set of 100 soil monoliths distributed on a regular grid of 5 m mesh. These data were analyzed in Rossi (2003a) and are published here with the aim that they could be reanalyzed using new statistical tools (e.g. MEM analyses see Jiménez et al. 2014) or serve as example for researchers that train on space-time statistical methods.

Summary The spatial distribution of two earthworm groups ( Sthulmania porifera and Chuniodrilus zielae (Eudrilidae) on the one part and Millsonia anomala (Megascolecidae) on the other part) was analysed using the SADIE system. Earthworms were sampled in November 1995 in a grass savanna at Lamto (Cote d'Ivoire) using 100 sampling points distributed in a square grid (mesh size 5 m). The investigated plot was a 45 × 45 m square. The global index of aggregation I a , available in the SADIE method, indicated that both groups were significantly clustered. Further analyses were conducted using the “Red-Blue” plots approach. This new method is based on a standardized and dimensionless index that makes it possible to identify patches and gaps. Results indicated the presence of significant patches for both groups. Clusters corresponded to areas of various size and shape. As an example, in M. anomala , patches and gaps represented respectively 22.8% and 17.6% of the total area under study. Size and shape of the observed clusters were very variable and contour maps of the clustering indices allowed visualizing of these structures. For the eudrilids, one patch and two gaps were reported while there were six patches and six gaps in the case of M. anomala . The spatial distribution of cluster centroids did not differ significantly from complete spatial randomness. In addition, no spatial association was reported between the clusters of these earthworm groups.

Summary The spatiotemporal pattern of a tropical earthworm assemblage (Lamto, Cote d'Ivoire) was assessed using a Partial Triadic Analysis (PTA). The abundance of earthworm species was estimated on five occasions covering two years within a single plot sampled with 100 sampling locations. The results showed that the earthworm community was highly structured in space and that the spatial pattern was stable through time. The Partial Triadic Analysis allowed extracting the earthworm community pattern that was common to all the dates. It was possible to identify which dates differed from the common model and which species were responsible for these discrepancies. The main pattern revealed by PTA was also submitted to spatial statistics to assess its significance. The results showed that the earthworm community is structured as a juxtaposition of patches dominated by different species. This pattern appeared to be constant during our 2-year study. When species were grouped following their impact upon soil structure dynamics the surveyed area appeared to be made of adjacent patches dominated either by compacting or decompacting earthworm species. The functional implications of this pattern are discussed and the spatial structure of the earthworm community was compared to soil bulk density distribution. The Mantel tests revealed a very strong relationship between soil bulk density and earthworm community structure.

Summary Populations of soil organisms and especially earthworms are spatially dependent at various scales. The present study was designed to assess the short-range spatial variability of different tropical earthworm populations in a savanna protected from fire for 15 years in the station d'Ecologie Tropicale of Lamto (Cote d'Ivoire). Earthworms were sampled in 1995 and 1996 using 75 and 98 25×25×10 cm soil monoliths respectively. Sampling points were distributed along a transect with minimum inter-sample distance of 50 cm. The earthworms displayed clear spatial structures either when density or biomass were analysed. Some variograms displayed two plateaux thus indicating the presence of two distinct scales of spatial autocorrelation. However small the minimum sample spacing, the nugget variance remained high, which indicated the high value of residual, small-scale variability. SADIE analyses were used to test for statistical significance of the spatial aggregation and clusters description.

Leptospirosis essentially affects human following contact with rodent urine-contaminated water. As such, it was mainly found associated with rice culture, recreational activities and flooding. This is also the reason why it has mainly been investigated in temperate as well as warm and humid regions, while arid zones have been only very occasionally monitored for this disease. In particular, data for West African countries are extremely scarce. Here, we took advantage of an extensive survey of urban rodents in Niamey, Niger, in order to look for rodent-borne pathogenic Leptospira species presence and distribution across the city. To do so, we used high throughput bacterial 16S-based metabarcoding, lipL32 gene-targeting RT-PCR, rrs gene sequencing and VNTR typing as well as GIS-based multivariate spatial analysis. Our results show that leptospires seem absent from the core city where usual Leptospira reservoir rodent species (namely R. rattus and M. natalensis) are yet abundant. On the contrary, L. kirschneri was detected in Arvicanthis niloticus and Cricetomys gambianus, two rodent species that are restricted to irrigated cultures within the city. Moreover, the VNTR profiles showed that rodent-borne leptospires in Niamey belong to previously undescribed serovars. Altogether, our study points towards the importance of market gardening in maintain and circulation of leptospirosis within Sahelian cities. In Africa, irrigated urban agriculture constitutes a pivotal source of food supply, especially in the context of the ongoing extensive urbanization of the continent. With this in mind, we speculate that leptospirosis may represent a zoonotic disease of concern also in arid regions that would deserve to be more rigorously surveyed, especially in urban agricultural settings., Author Summary We surveyed rodent-borne Leptospira in rodents from Niamey, the capital town of Niger, using bacterial metabarcoding, RT-PCR, sequencing, VNTR typing and GIS-based geostatistics. Two new serovars of Leptospira kirschneri were identified in Arvicanthis niloticus and Cricetomys gambianus, two species that inhabit exclusively urban irrigated gardens. Since no rodent-borne leptospires could be found in the core city, our results point towards the importance of urban agriculture in the maintaining and the circulation of these bacteria in cities from semi-arid regions where they are usually poorly documented and even hardly looked for. Accordingly, this is one of the very rare mentions of these zoonotic agents in Sahel, and the first one in Niger. Keeping in mind the critical role of urban gardening for food security in extensively growing West African cities, we believe that leptospirosis should be more closely scrutinized in Sahelian countries where numerous cases of human fevers are of unknown origin.

International audience; The brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae), has emerged as a harmful invasive insect pest in North America and Europe in the 1990s and 2000s, respectively. Native to eastern Asia, this highly polyphagous pest (> 120 different host plants) is spreading rapidly worldwide, notably through human activities. The increasing global importance of the pest suggests that more coordinated actions are needed to slow its spread and mitigate negative effects in invaded areas. Prevention of large-scale outbreaks will require accurate identification and effective mitigation tools to be rapidly developed and widely implemented. In this short review, we update the current distribution of H. halys, discuss potential geographic range expansion based on passive and active dispersal and provide insight on the economic, environmental and social impact associated with H. halys.

International audience; This chapter presents the evolutionary history of Thaumetopoea species associated with pines, at different temporal and spatial scales. It corresponds to recent discoveries and ongoing works using sequencing technologies and population genetics. Most of the subchapters focus on the winter pine processionary moths T. pityocampa/T. wilkinsoni including a population with a shifted life cycle. Results concerning the summer pine processionary moth T. pinivora and the evolution of the whole genus are also presented. This chapter gives insights about the effects of Quaternary climate changes in different regions, and allow to study the contemporary changes due to the present climate warming.

International audience; Widely distributed species often show strong phylogeographic structure, with lineages potentially adapted to different biotic and abiotic conditions. The success of an invasion process may thus depend on the intraspecific identity of the introduced propagules. However, pest risk analyses are usually performed without accounting for intraspecific diversity. In this study, we developed bioclimatic models using MaxEnt and boosted regression trees approaches, to predict the potential distribution in Europe of six economically important Tephritid pests (Ceratitis fasciventris (Bezzi), Bactrocera oleae (Rossi), Anastrepha obliqua (Macquart), Anastrepha fraterculus (Wiedemann), Rhagoletis pomonella (Walsh) and Bactrocera cucurbitae (Coquillet)). We considered intraspecific diversity in our risk analyses by independently modeling the distributions of conspecific lineages. The six species displayed different potential distributions in Europe. A strong signal of intraspecific climate envelope divergence was observed in most species. In some cases, conspecific lineages differed strongly in potential distributions suggesting that taxonomic resolution should be accounted for in pest risk analyses. No models (lineage- and species-based approaches) predicted high climatic suitability in the entire invaded range of B. oleae-the only species whose intraspecific identity of invading populations has been elucidated-in California. Host availability appears to play the most important role in shaping the geographic range of this specialist pest. However, climatic suitability values predicted by species-based models are correlated with population densities of B. oleae globally reported in California. Our study highlights how classical taxonomic boundaries may lead to under- or overestimation of the potential pest distributions and encourages accounting for intraspecific diversity when assessing the risk of biological invasion.

[Background] Studying the drivers and determinants of species, population and community spatial patterns is central to ecology. The observed structure of community assemblages is the result of deterministic abiotic (environmental constraints) and biotic factors (positive and negative species interactions), as well as stochastic colonization events (historical contingency). We analyzed the role of multi-scale spatial component of soil environmental variability in structuring earthworm assemblages in a gallery forest from the Colombian “Llanos”. We aimed to disentangle the spatial scales at which species assemblages are structured and determine whether these scales matched those expressed by soil environmental variables. We also tested the hypothesis of the “single tree effect” by exploring the spatial relationships between root-related variables and soil nutrient and physical variables in structuring earthworm assemblages. Multivariate ordination techniques and spatially explicit tools were used, namely cross-correlograms, Principal Coordinates of Neighbor Matrices (PCNM) and variation partitioning analyses., [Results] The relationship between the spatial organization of earthworm assemblages and soil environmental parameters revealed explicitly multi-scale responses. The soil environmental variables that explained nested population structures across the multi-spatial scale gradient differed for earthworms and assemblages at the very-fine- (30 m), fine (10–20 m) and very fine scales (, [Conclusions] A large proportion of the spatial variation did not depend on the soil environmental variability for certain species. This finding could indicate the influence of contagious biotic interactions, stochastic factors, or unmeasured relevant soil environmental variables., This study was financed by the DIVERSITAS program and CIAT (Soils Unit). We are particularly grateful for the useful comments provided by R. J. Thomas and I. Rao and for the continuous support of soil ecology studies by E. Amézquita. We also gratefully acknowledge the help provided by field and lab research assistants at CIAT. We thank Dr. J. Perry at Rothamsted for kindly providing SADIE software and the ARAID foundation for support to the first author. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). Finally, we are grateful for the insightful comments and valuable suggestions provided by two reviewers, which improved an early version of the manuscript.

Times Cited: 0; International audience; Invasive rodents have been responsible for the diffusion worldwide of many zoonotic agents, thus representing major threats for public health. Cities are important hubs for people and goods exchange and are thus expected to play a pivotal role in invasive commensal rodent dissemination. Yet, data about urban rodents' ecology, especially invasive vs. native species interactions, are dramatically scarce. Here, we provide results of an extensive survey of urban rodents conducted in Niamey, Niger, depicting the early stages of rodent bioinvasions within a city. We explore the species-specific spatial distributions throughout the city using contrasted approaches, namely field sampling, co-occurrence analysis, occupancy modelling and indicator geostatistics. We show that (i) two species (i.e. rural-like vs. truly commensal) assemblages can be identified, and that (ii) within commensal rodents, invasive (Rattus rattus and Mus musculus) and native (Mastomys natalensis) species are spatially segregated. Moreover, several pieces of arguments tend to suggest that these exclusive distributions reflect an ongoing native-to-invasive species turn over. The underlying processes as well as the possible consequences for humans are discussed.

Ficus and their species-specific pollinator wasps (Agaonidae) form a remarkable plant–insect obligate mutualism. Each monoecious fig species also shelters a community of nonpollinating chalcids, composed of both gallmakers and parasitoids. The few previous studies that took these species into account aimed at determining their potential effect on the mutualism. To go further, we argue that the fig wasps represent an interesting model for studies of community ecology. Figs and fig wasps of different groups were studied in Cote d'Ivoire to quantify local ecological interactions. Regardless of their fig host or taxonomical position, we identified three ecological groups of nonpollinating fig wasps on the basis of their timing of oviposition in the fig and on their oviposition behavior. Pollinating and nonpollinating fig wasps were shown to interact intimately, and to have a significant effect on the host plant in at least some cases. Each species of the community seems to preferentially oviposit in a part of the female flowers, depending on their depth inside the fig. Convergence in fig exploitation thus exists in various chalcid lineages, and the community structure and organization are very similar between fig species. Concepts developed in parasitoid community ecology could now be tested on this promising model.

The relationships between soil nematodes and soil texture, carbon content and depth were assessed in both a cultivated and uncultivated plots. Simple correlation coefficient analyses indicated a negative linear correlation between the plant-parasitic species Helicotylenchus retnsus Siddiqui and Brown and soil clay content in the uncultivated site. However, Mantel Lests showed this correlation to be spurious and only due to the presence of a common spatial pattern in the variables distribution. Both H. retusus density and soil clay content appeared to be independently driven by a common, unknown cause. The use of suitable statistical methods to analyse spatially dependent variables proved to be particularly fruitful in that they prevent spurious correlations and allow us to test different causal models involving the set of variables at hand.

The spatial distribution of seven earthworm species from the Lamto savannas (Cote d'lvoire) was investigated by Taylor's Power Law. The method yielded aggregation indices highly correlated with species demographic and morphological parameters. A Principal Component Analysis showed that the smaller an earthworm species was and the higher its annual fecundity, the more its spatial distribution was aggregated. Mapping of some species density showed the diversity of spatial patterns in the field.

International audience; Rodents are involved in the epidemiology of many pathogens and are major pests for agriculture. Local perception and beliefs about rodents and their damages is a key element of control programs. We here present the first survey focusing on the human perception of rodent-associated problems in an African town, namely Niamey, Niger. In total, 170 interviews were conducted in 18 different urban districts where rodents (Mastomys natalensis, Rattus rattus and Mus musculus) are widespread and abundant. Rodent-associated problems were mentioned in almost all instances (96.5 %). Eight different categories of rodent-induced nuisances could be recurrently identified. The most frequently cited one consists in damages on food and food stocks (63.1 %), followed by damages on houses (47.3 %), furniture (19.5 %) and clothes (16.8 %). There was no significant association between damages and districts, which means that the perception of rodent-associated problems did not vary significantly across the city. Our survey strongly suggests that rodents may represent major pests not only for farmers, but also for inhabitants of towns, thus contributing to reinforce economic vulnerability. Finally, no mention of sanitary or medical problems was ever recorded during our survey, thus pointing towards an apparent absence of knowledge about the potential role of rodents in some public health issues.

International audience; The leaf-curl plum aphid, Brachycaudus helichrysi (Kaltenbach 1843), is a polyphagous cosmopolitan aphid. This serious pest of plum and peach orchards affects the growth of its host plants by curling infested leaves, and can transmit viruses such as the plum pox virus. Phylogenetic analyses have recently shown that B. helichrysi actually comprises two lineages that are morphologically similar but genetically different. In this study, we developed a PCR-RFLP test for differentiating between these two lineages, based on a mitochondrial DNA fragment. We used this test to investigate the patterns of host plant association and the geographical distribution of these lineages, with a large sample of individuals collected from numerous host plants and locations worldwide. We found that one of the lineages was never present on plum trees, and that individuals from both lineages coexisted on many secondary herbaceous hosts at almost all of the sites studied. We then carried out principal component analysis to determine whether the distribution of the two lineages could be explained by climatic features. We found that the lineage absent from plum trees was not found in regions with harsh winters. This suggests that one of the lineages within B. helichrysi may be an obligate parthenogenetic aphid.

42 páginas, 4 tablas y 3 figuras + 1 apéndice de 7 pàginas, [EN] Disentangling how communities of soil organisms are deterministically structured by abiotic and biotic factors is of utmost relevance, and few data sets on co-occurrence patterns exist in soil ecology compared to other disciplines. In this study, we assessed species spatial co-occurrence and niche overlap together with the heterogeneity of selected soil properties in a gallery forest (GF) of the Colombian Llanos. We used null-model analysis to test for non-random patterns of species co-occurrence and body size in assemblages of earthworms and whether the pattern observed was the result of environmental heterogeneity or biotic processes structuring the community at small scales by means of co-inertia analysis (CoIA). The results showed that earthworm species co-occurred more frequently than expected by chance at short distances, and CoIA highlighted a significant specific relationship between earthworm species and soil variables. The effect of soil environmental heterogeneity on one litter-feeding species but also the impact of soil-feeding species on soil physical properties was revealed. Correlogram analysis on the first axis extracted in the CoIA showed the scale of the common structure shared by the fauna and soil variable tables. The earthworm community was not deterministically structured by competition and co-occurrence of competing species was facilitated by soil environmental heterogeneity at small scales in the GF. Our results agreed with the coexistence aggregation model which suggests that spatial aggregation of competitors at patchily distributed resources (environment) can facilitate species coexistence., Local names for tree species of the gallery forest are those specifi cally used in the region. h anks are extended to Richard J. h omas, Idupulapati Rao and Edgar Am é zquita (CIAT) and Patrick Lavelle (IRD) for fi nancial and logistic support during fi eld work. We thank fi eld assistants Jose Garc í a, Salvador Rojas and Guillermo Murcia for sharing their knowledge and research assistant Jaumer Ricaute for root analysis at CIAT lab.

Evolution may improve the invasiveness of populations, but it often remains unclear whether key adaptation events occur after introduction into the recipient habitat (i.e. post-introduction adaptation scenario), or before introduction within the native range (i.e. prior-adaptation scenario) or at a primary site of invasion (i.e. bridgehead scenario). We used a multidisciplinary approach to determine which of these three scenarios underlies the invasion of the tropical ant Wasmannia auropunctata in a Mediterranean region (i.e. Israel). Species distribution models (SDM), phylogeographical analyses at a broad geographical scale and laboratory experiments on appropriate native and invasive populations indicated that Israeli populations followed an invasion scenario in which adaptation to cold occurred at the southern limit of the native range before dispersal to Israel. We discuss the usefulness of combining SDM, genetic and experimental approaches for unambiguous determination of eco-evolutionary invasion scenarios. Fil: Rey, Olivier. Institut National de la Recherche Agronomique; Francia Fil: Estoup, Arnaud. Institut National de la Recherche Agronomique; Francia Fil: Vonshak, Merav. Universidad de Tel Aviv; Israel Fil: Loiseau, Anne. Institut National de la Recherche Agronomique; Francia Fil: Blanchet, Simon. Centre National de la Recherche Scientifique; Francia Fil: Calcaterra, Luis Alberto. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Chifflet, Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Rossi, Jean Pierre. Institut National de la Recherche Agronomique; Francia Fil: Kergoat, Gaël J.. Institut National de la Recherche Agronomique; Francia Fil: Foucaud, Julien. Institut National de la Recherche Agronomique; Francia Fil: Orivel, Jérôme. Centre National de la Recherche Scientifique; Francia Fil: Leponce, Maurice. Royal Belgian Institute Of Natural Sciences; Bélgica Fil: Schultz, Ted. Smithsonian Institute Natural Museum Of Natural History; Estados Unidos Fil: Facon, Benoit. Institut National de la Recherche Agronomique; Francia

International audience; 1 Various factors such as climate and resource availability influence the geographical distributions of organisms. Species sensitive to small temperature variations are known to experience rapid distribution shifts as a result of current global warming, sometimes leading to new threats to agriculture and forests. Tomicus piniperda and Tomicus destruens (Coleoptera, Curculionidae, Scolytinae) cause economic damage to pines in Europe and around the Mediterranean Basin. However, their respective potential distributions have not yet been studied at a large scale. The present study aimed to investigate the influence of climatic and host factors on the geographical distributions of both Tomicus species in Europe and around the Mediterranean Sea, and to establish maps of suitable areas. 2 Using 114 published localities where the presence or absence of both species was unambiguously recorded, we gathered WorldClim meteorological records to correlate the occurrence of insects with bioclimatic variables and to build potential distribution maps. 3 The two studied Tomicus species presented parapatric distributions and opposite climate demands, with T. destruens occurring in locations with warmer temperatures, whereas T. piniperda occurs under a colder climate. Amongst the investigated climate variables, temperature appeared to be most correlated with both species distributions. 4 The potential ranges of both species were further restricted by the availability of pine hosts. It appeared that setting new pine plantations in regions where T. destruens or T. piniperda are still absent could favour a rapid expansion of their distributions. Our data will be useful when aiming to apply management strategies adapted to each species, and to forecast their potential range expansions/contractions as a result of climate warming.

International audience; Planting exotic conifers offers indigenous forest insects an opportunity to extend their host range and eventually to become significant pests. Knowing the ecological and evolutionary modalities driving the colonisation of exotic tree species by indigenous insects is thus of primary importance. We compared the bark beetle communities (Coleoptera: Curculionidae, Scolytinae) associated with both native and introduced conifers in France. The aim of our study was to estimate the influence of both host- and insect-related factors on the beetles’ likelihood to shift onto new hosts. We considered the influence of host origin (i.e. native vs. exotic), host tree species identity, tree bark thickness and tree taxonomic proximity, as well as insects’ host specificity. A field inventory using trap trees was carried out in two regions in France (Limousin and Jura) during two consecutive years (2006 and 2007) on three European native conifer species [Norway spruce (Picea abies); Scots pine (Pinus sylvestris) and European Silver-fir (Abies alba)] and five North American [Sitka spruce (Picea sitchensis); Eastern white pine (Pinus strobus); Grand fir (Abies grandis); Douglas fir (Pseudotsuga menziesii) and Western red cedar (Thuja plicata)]. A total of 18 indigenous and 2 exotic bark beetle species were collected. All exotic conifer species were colonised by indigenous bark beetle species and no significant difference was observed of the cumulated species richness of the latter between native and exotic tree species (13 vs. 14, P < 0.05). The ability of indigenous bark beetles to shift onto exotic conifers appeared to strongly depend on host species (significantly structuring bark beetle assemblages), the presence of phylogenetically related native conifer species and that of similar resources, in combination with insect host specificity. Host tree species status (native or exotic) also seemed to be involved, but its effect did not seem as essential as that of the previous factors. These findings are discussed in terms of adaptation, plasticity and practical aspects of forest management.

International audience; Spatial genetic analyses can be used to infer dispersal processes in natural populations. For partially clonal species with alternating sexual and asexual reproduction, the repetition of genotypes must be taken into account in analyses. The methods currently employed to evaluate the relevance of the spatial scale used for the estimation of gene flow are not suitable for these species. We investigated recently developed methods for taking into account repeated genotypes and for determining whether the sampling scale is large enough to capture all the spatial genetic structure existing within a population. We applied these methods to a fungal plant pathogen species, Cryphonectria parasitica, which has caused the death of many American and European chestnut trees since its introduction from Asia at the beginning of the 20th century. These methods were found to be useful for unravelling the effects of clonality and historical gene flow on the spatial genetic structure, and indicated that dispersal processes have probably occurred over a larger spatial scale than previously assumed.

Aim To evaluate the joint and independent effects of spatial location, landscape composition and landscape structure on the distribution patterns of bird and carabid beetle assemblages in a mosaic landscape dominated by pine plantation forests. Location A continuous 3000-ha landscape mosaic with native maritime pine Pinus pinaster plantations of different ages, deciduous woodlands and open habitats, located in the Landes de Gascogne forest of south-western France. Methods We sampled breeding birds by 20-min point counts and carabid beetles by pitfall trapping using a systematic grid sampling of 200 points every 400 m over the whole landscape. Explanatory variables were composed of three data sets derived from GIS habitat mapping: (1) spatial variables (polynomial terms of geographical coordinates of samples), (2) landscape composition as the percentage cover of the six main habitats, and (3) landscape structure metrics including indices of fragmentation and spatial heterogeneity. We used canonical correspondence analysis with variance partitioning to evaluate the joint and independent effects of the three sets of variables on the ordination of species assemblages. Moran's I correlograms and Mantel tests were used to assess for spatial structure in species distribution and relationships with separate landscape attributes. Results Landscape composition was the main factor explaining the distribution patterns of birds and carabids at the mesoscale of 400 × 400 m. Independent effects of spatial variables and landscape structure were still significant for bird assemblages once landscape composition was controlled for, but not for carabid assemblages. Spatial distributions of birds and carabids were primarily influenced by the amount of heathlands, young pine plantations, herbaceous firebreaks and deciduous woodlands. Deciduous woodland species had positive responses to edge density, while open habitat species were positively associated with mean patch area. Main conclusions Forest birds were favoured by an increase in deciduous woodland cover and landscape heterogeneity, but there was no evidence for a similar effect on carabid beetles. Fragmentation of open habitats negatively affected both early-successional birds and carabids, specialist species being restricted to large heathlands and young plantations. Several birds of conservation concern were associated with mosaics of woodlands and grasslands, especially meadows and firebreaks. Conserving biodiversity in mosaic plantation landscapes could be achieved by the maintenance of a significant amount of early-successional habitats and deciduous woodland patches within a conifer plantation matrix.

Classical predator–prey or host–parasitoid models often lead to spatial self-organization due to local interactions and limited dispersal ability of the resource (prey or host) and consumers (predator or parasitoid). We hypothesized that self-organization may also arise in soil organisms when the resource is passive and has a constant renewal rate. Earthworm density is correlated with soil properties, but soil heterogeneity only explains a small proportion of spatial variations in earthworm densities. We hypothesized that this could be partially due to self-organization. These two hypotheses were tested with an original model parameterized for a savannah earthworm population. The model simulates an earthworm population divided in 1 m2 cells. It is based on the assumption that fine soil aggregates constitute the only limiting resource influencing mortality, fecundity and dispersal and that this resource is renewed according to a constant rate independent of earthworm dynamics. Simulations lead to aggregated spatial distributions when the sensitivity of mortality or fecundity to the availability of the limiting resource is high, and when earthworm mobility is low. Such parameters values are consistent with what is known about earthworm biology. Applicability to different ecological systems and resulting population dynamical properties are discussed.

International audience; Earthworms often form spatially structured populations characterised by alternate clusters of either low or high density. This study compared various soil properties and herbaceous plant biomass between areas of high and low earthworm density (i.e. patches and gaps) in a tropical grassland (la Mancha, Veracruz, Mexico). We aimed at identifying those variables that might explain the observed spatial distribution or, conversely be explained by the community pattern. We examined the spatial aggregation by means of the Spatial Analysis by Distance IndicEs (SADIE) system and showed the presence of significant patches and gaps. Only a few variables significantly differed between patches and gaps. Areas corresponding to earthworm patches and gaps had more silt and clay, respectively, in the 10–30 cm soil layer. There was no difference in the C content in the different particle-size classes expressed in absolute values (mg C g−1 soil) but the proportion of C associated to > 200 μm particles was larger in the patches (0–10 cm layer) while there was more C associated to the fine particle (< 50 μm) in the gaps (10–30 cm soil layer). Patches and gaps did not differ significantly in terms of cation concentrations (K, Mg and Ca), pH, soil bulk density or herbaceous plant dry mass. The lack of clear relationships between earthworm distribution and soil parameters in this study suggest that earthworm populations and soil properties may occur at different spatial scales

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; A comparative study of the spatial distributions and the quantity of biogenic structures produced by earthworms and termites (Odontotermes nilensis and Ancistrotermes guineensis) has been conducted in a mango orchard at Thiès (Senegal).This study showed that surface biogenic structures may represent a large amount of modified soil (up to 536.5 g m−2) which vary depending upon the seasons and the species. Whilst the quantity of casts was independent on the season (178.6 g m−2), O. nilensis sheetings fluctuated with the seasons. In addition, we show that the spatial organisation of surface biogenic structures fluctuates with seasons. It displays patches ranging from 5 to 15 m. There is a link between the distribution of earthworm casts and the vegetation. In addition, spatial distribution was also linked to the biology of constructing species. We observed that the A. guineensis’ filling structures were mainly located under the mango trees during the dry season where the stems and the brushwoods were abundant. It appears that the spatio-temporal distribution of the biogenic structures under study depended upon two main factors: season and vegetation. However, depending upon the biology of the engineer, these two factors influenced the spatial distribution of structures in different ways

International audience; It is now attested that a large part of the Amazonian rain forest has been cultivated during Pre-Colombian times, using charcoal as an amendment. The incorporation of charcoal to the soil is a starting point for the formation of fertile Amazonian Dark Earths, still selected by Indian people for shifting cultivation. We showed that finely separated charcoal was commonly incorporated in the topsoil by Pontoscolex corethrurus, a tropical earthworm which thrives after burning and clearing of the rain forest, and that this natural process could be used to improve tropical soil fertility. Our paper is a contribution to the present debate about (i) the origin of black carbon in fertile Dark Earths, (ii) the detrimental vs favourable role of Pontoscolex corethrurus in tropical agriculture, (iii) natural processes which might be used to increase tropical soil fertility.

International audience; Soil macrofauna was surveyed in six sites characterised by different vegetation types on five occasions in the Western Ghats, India. Sampling sites included a primary forest, a weakly disturbed forest (slightly logged in the past), a highly disturbed forest (intensively logged), an Acacia auriculiformis plantation (8 years old), a pasture with high density of Phoenix humilis and a pasture without P. humilis. We showed that both land management and temporal variability induced significant changes in the soil macrofauna. Forest sites hosted larger densities of soil macroorganisms. The effect of seasons was apparent as some clear modifications in the fauna composition occurred. Some groups like earthwonns mainly exhibited temporal variability whereas others like millipedes were chiefly affected by land management options. The seasonal rhythms of soil macrofauna were poorly expressed in the pasture plots and the Acacia plantation, but were particularly clear in the forest sites. This interaction between land management and temporal patterns may be explained by some changes in the species composition associated with certain land-uses. Our approach was based on a between-within classes PCA that proved particularly useful by providing statistical tests and a hierarchy of land management and temporal rhythm effects

International audience; This chapter synthesizes information on the effects of earthworms on soil systems at scales longer than 1 year, and earthworm behavior that may affect these processes is detailed

The spatiotemporal pattern of a tropical earthworm assemblage (Lamto, Cote d'Ivoire) was assessed using a Partial Triadic Analysis (PTA). The abundance of earthworm species was estimated on five occasions covering two years within a single plot sampled with 100 sampling locations. The results showed that the earthworm community was highly structured in space and that the spatial pattern was stable through time. The Partial Triadic Analysis allowed extracting the earthworm community pattern that was common to all the dates. It was possible to identify which dates differed from the common model and which species were responsible for these discrepancies. The main pattern revealed by PTA was also submitted to spatial statistics to assess its significance. The results showed that the earthworm community is structured as a juxtaposition of patches dominated by different species. This pattern appeared to be constant during our 2-year study. When species were grouped following their impact upon soil structure dynamics the surveyed area appeared to be made of adjacent patches dominated either by compacting or decompacting earthworm species. The functional implications of this pattern are discussed and the spatial structure of the earthworm community was compared to soil bulk density distribution. The Mantel tests revealed a very strong relationship between soil bulk density and earthworm community structure.

Populations of soil organisms and especially earthworms are spatially dependent at various scales. The present study was designed to assess the short-range spatial variability of different tropical earthworm populations in a savanna protected from fire for 15 years in the station d'Ecologie Tropicale of Lamto (Cote d'lvoire). Earthworms were sampled in 1995 and 1996 using 75 and 98 25 x 25 x 10 cm soil monoliths respectively. Sampling points were distributed along a transect with minimum inter-sample distance of 50 cm. The earthworms displayed clear spatial structures either when density or biomass were analysed. Some variograms displayed two plateaux thus indicating the presence of two distinct scales of spatial autocorrelation. However small the minimum sample spacing, the nugget variance remained high, which indicated the high value of residual, small-scale variability. SADIE analyses were used to test for statistical significance of the spatial aggregation and clusters description.

29 páginas, 4 figuras, 4 tablas., The horizontal spatial distribution of earthworms in a native savanna and in a 17 year introduced pasture from the area of Carimagua (Colombia) was assessed by means of aggregation indices and geostatistical analysis. Morisita’s index (Id) and Taylor’s index (b) were calculated from field data obtained through 1 m2 quadrats during a sampling period of 17 months and both semivariograms and contour maps were obtained at three different dates through a rapid sampling of 64, cm soil blocks, regularly distributed in the nodes of a 8×8 grid (i.e. m). Earthworms tended to exhibit contagious distribution in both land use systems and a multivariate relationship appeared between the size of the earthworm and aggregation indices employed. Land use had no significant effect on the spatial distribution of earthworms. Earthworms belonging to different ecological categories and from diverse sizes were spatially distributed in patches of several tens of meters. Semivariograms reflected, occasionally, the size of these patches, although, no spatial structure was perceived at some dates. This might be due to the intersample distance employed (10 m) so that changing the scale of observation could reflect unseen patterns. In this study our purpose was first to determine the strength of spatial aggregation in some Neotropical earthworm species and then to observe the movement of population patches at the scale of the studied area. The use of these types of spatial analyses in conjunction may be very useful to establish the dynamics of earthworm populations in the field., This study was included within the Macrofauna Project from the STD-2 EC. The first author wants to thank CIAT (International Center for Tropical Agriculture) for technical and human support during all the study period. The first author acknowledges T. Decaëns and two anonymous referees for their helpful comments on earlier versions of this paper.

The spatial pattern of four species of plant-parasitic nematodes in a sugarcane crop in Martinique was analysed using geostatistics. Aggregation of populations was first described with the variance to mean ratio and Morisita's index. The indices showed that nematodes had clumped distributions. Geostatistical analysis demonstrated that the nematode data were autocorrelated and allowed a fine description of the species density patterns. Correspondence analysis was used to ordinate the data and showed the presence of an antagonism between Criconemella onoensis and the other species. A cross semi-variogram indicated a negative cross correlation between the pattern of Criconemella onoensis and the pattern of the sum of the other species present at the study site.