Metacommunity Dynamics: Decline of Functional Relationship along a Habitat Fragmentation Gradient

Background: The metacommunity framework is crucial to the study of functional relations along environmental gradients. Changes in resource grain associated with increasing habitat fragmentation should generate uncoupled responses of interacting species with contrasted dispersal abilities. Methodology/Principal Findings: Here we tested whether the intensity of parasitism was modified by increasing habitat fragmentation in the well know predator-prey system linking the parasitoid Cotesia glomerata (Hymenoptera: Braconidae) to its main host Pieris brassicae (Lepidoptera: Pieridae). We collected information on herbivorous abundance and parasitism rate along an urbanization gradient from the periphery to the centre of Paris. We showed that butterfly densities were not influenced by habitat fragmentation, whereas parasitism rate sharply decreased along this gradient. Conclusions/Significance: Our results provide novel insights into the mechanisms underlying the persistence of species in highly fragmented areas. They suggest that differential dispersal abilities could alter functional relationships between prey and predator, notably by a lack of natural predators

Coupling inter-patch movement models and landscape graph to assess functional connectivity

Landscape connectivity is a key process for the functioning and persistence of spatially-structured populations in fragmented landscapes. Butterflies are particularly sensitive to landscape change and are excellent model organisms to study landscape connectivity. Here, we infer functional connectivity from the assessment of the selection of different landscape elements in a highly fragmented landscape in the Île-de-France region (France). Firstly we measured the butterfly preferences of the Large White butterfly (Pieris brassicae) in different landscape elements using individual release experiments. Secondly, we used an inter-patch movement model based on butterfly choices to build the selection map of the landscape elements to moving butterflies. From this map, functional connectivity network of P. brassicae was modelled using landscape graph-based approach. In our study area, we identified nine components/groups of connected habitat patches, eight of them located in urbanized areas, whereas the last one covered the more rural areas. Eventually, we provided elements to validate the predictions of our model with independent experiments of mass release-recapture of butterflies. Our study shows (1) the efficiency of our inter-patch movement model based on species preferences in predicting complex ecological processes such as dispersal and (2) how inter-patch movement model results coupled to landscape graph can assess landscape functional connectivity at large spatial scale

Influence of discharge, hydraulics, water temperature, and dispersal on density synchrony in brown trout populations (Salmo trutta)

International audienceLes facteurs environnementaux peuvent causer des fluctuations synchrones de densités entre populations. Une meilleure compréhension des processus expliquant la synchronie est fondamentale pour prédire des pertes de résilience des métapopulations sujettes à des changements environnementaux. Nous étudions la synchronie des chroniques de densités de trois classes d’âge de la truite brune (Salmo trutta) (0+, 1+ et adultes) entre 36 tronçons de cours d’eau. Nous utilisons des tests de Mantel pour discriminer les effets relatifs de la proximité géographique, de la synchronie de variables environnementales clefs (débit, température de l’eau, conditions hydrauliques et mobilité du substrat) et de la dispersion densité-dépendante. La synchronie environnementale expliquait fortement la synchronie de la truite jusqu’à des distances de 75 km. Cet effet était dû en partie à l’influence négative sur les 0+ des hauts débits pendant l’émergence et une influence de la mobilité du substrat pendant la période de ponte. La dispersion entre tronçon influençait faiblement nos résultats. Les densités de juvéniles et d’adultes étaient fortement structurées par des processus de survie, mais n’étaient pas influencées par la synchronie des conditions environnementales. Les résultats suggèrent que l’environnement peut avoir des effets généraux sur la dynamique de population qui peuvent influencer la résilience des métapopulation

Are Amphipod invaders a threat to the regional biodiversity? Conservation prospects for the Loire River

The impact of invasions on local biodiversity is well established, but their impact on regional biodiversity has so far been only sketchily documented. To address this question, we studied the impact at various observation scales (ranging from the microhabitat to the whole catchment) of successive arrivals of non-native amphipods on the amphipod assemblage of the Loire River basin in France. Amphipod assemblages were studied at 225 sites covering the whole Loire catchment. Non-native species were dominant at all sites in the main channel of the Loire River, but native species were still present at most of the sites. We found that the invaders have failed to colonize most of tributaries of the Loire River. At the regional scale, we found that since the invaders first arrived 25 years ago, the global amphipod diversity has increased by 33% (from 8 to 12 species) due to the arrival of non-native species. We discuss the possibility that the lack of any loss of biodiversity may be directly linked to the presence of refuges at the microhabitat scale in the Loire channel and in the tributaries, which invasive species have been unable to colonize. The restoration of river quality could increase the number of refuges for native species, thus reducing the impact of invader

Triptans attenuate capsaicin-induced CREB phosphorylation within the trigeminal nucleus caudalis: a mechanism to prevent central sensitization?

The c-AMP-responsive element binding protein (CREB) and its phosphorylated product (P-CREB) are nuclear proteins expressed after stimulation of pain-producing areas of the spinal cord. There is evidence indicating that central sensitization within dorsal horn neurons is dependent on P-CREB transcriptional regulation. The objectives of the study were to investigate the expression of P-CREB in cells in rat trigeminal nucleus caudalis after noxious stimulation and to determine whether pre-treatment with specific anti-migraine agents modulate this expression. CREB and P-CREB labelling was investigated within the trigeminal caudalis by immunohistochemistry after capsaicin stimulation. Subsequently, the effect of i.v. pre-treatment with either sumatriptan (n = 5), or naratriptan (n = 7) on P-CREB expression was studied. Five animals pre-treated with i.v. normal saline were served as controls. CREB and P-CREB labelling was robust in all animal groups within Sp5C. Both naratriptan and sumatriptan decreased P-CREB expression (p = 0.0003 and 0.0013) within the Sp5C. Triptans attenuate activation of CREB within the central parts of the trigeminal system, thereby leading to potential inhibition of central sensitization. P-CREB may serve as a new marker for post-synaptic neuronal activation within Sp5C in animal models relevant to migraine

The Citizen Science Paradox

International audienceCitizen science (CS) is now very popular in ecology. The number of scientific publications referencing CS has increased steadily over the past 15 years, with more than 1150 publications today. However, the multiplicity of research involved suggests that this number is highly underestimated. Based on this paradox, a literature review on CS shows that while its formalization in 2009 facilitated its referencing, about 70% of the publications are not referenced using CS as keyword. To understand this under-representation, an analysis of 149 publications related to the famous Christmas Bird Count program shows that this underestimation is not mainly related to the diversity of keywords used to describe CS, but rather to the fact that CS is mainly considered as a method (four publications out of five). The results also show that taking into account the whole text of a publication would represent a substantial improvement for the analysis of scientific databases, whatever the field of research

Hydrological drivers of brown trout population dynamics in France

Alteration of natural river flow regimes is a major threat to freshwater biodiversity. Restoration of natural flow regimes requires an understanding of linked hydrological and ecological processes. In this study, we investigated how annual seasonal flow characteristics and physical habitat attributes could interact to explain yearly changes in brown trout population densities (for 0+ fish, corresponding to the young of the year, and for the >0+ age class) in 112 sites widespread in France. Using an information theoretic approach and general linear modeling, we identified the physical habitat attributes and seasonal hydrological variables which explained 0+ proportion, total, >0+ and 0+ brown trout density dynamics. A decrease in total and 0+ brown trout densities were mainly linked to high water levels in both high and low flows during the emergence period and to a lesser extent, to physical habitat attributes reflecting the river size. 0+ proportions were only linked to the level of low flows, and to a lesser extent to high flows, during the emergence period. Our study demonstrated that seasonality of flow is a main driver of brown trout population dynamics, especially magnitude of high and low flows for the 0+ age class, and should be considered in the definition of environmental flows

When local extinction and colonization of river fishes can be predicted by regional occupancy ::the role of spatial scales

Background : Predicting which species are likely to go extinct is perhaps one of the most fundamental yet challenging tasks for conservation biologists. This is particularly relevant for freshwater ecosystems which tend to have the highest proportion of species threatened with extinction. According to metapopulation theories, local extinction and colonization rates of freshwater subpopulations can depend on the degree of regional occupancy, notably due to rescue effects. However, relationships between extinction, colonization, regional occupancy and the spatial scales at which they operate are currently poorly known. Methods : And Findings: We used a large dataset of freshwater fish annual censuses in 325 stream reaches to analyse how annual extinction/colonization rates of subpopulations depend on the regional occupancy of species. For this purpose, we modelled the regional occupancy of 34 fish species over the whole French river network and we tested how extinction/colonization rates could be predicted by regional occupancy described at five nested spatial scales. Results show that extinction and colonization rates depend on regional occupancy, revealing existence a rescue effect. We also find that these effects are scale dependent and their absolute contribution to colonization and extinction tends to decrease from river section to larger basin scales. Conclusions : In terms of management, we show that regional occupancy quantification allows the evaluation of local species extinction/colonization dynamics and reduction of local extinction risks for freshwater fish species implies the preservation of suitable habitats at both local and drainage basin scales

Advances in landscape ecology in urban areas.

International audienc

Advances in landscape ecology in urban areas.

International audienc