Persistence of butterfly populations in fragmented habitats along urban density gradients: motility helps

In a simulation study of genotypes conducted over 100 generations for more than 1600 butterfly’s individuals, we evaluate how the increase of anthropogenic fragmentation and reduction of habitat size along urbanisation gradients (from 7% to 59% of impervious land cover) influences genetic diversity and population persistence in butterfly species. We show that in areas characterised by a high urbanisation rate (> 56% impervious land cover), a large decrease of both genetic diversity (loss of 60-80% of initial observed heterozygosity) and population size (loss of 70-90% of individuals) is observed over time. This is confirmed by empirical data available for the mobile butterfly species Pieris rapae in a sub-part of the study area. Comparing simulated data for P. rapae with its normal dispersal ability and with a reduced dispersal ability, we also show that a higher dispersal ability can be an advantage to survive in an urban or highly fragmented environment. The results obtained here suggest that it is of high importance to account for population persistence, and confirm that it is crucial to maintain habitat size and connectivity in the context of land-use planning

Nested patterns in urban butterfly species assemblages : respective roles of plot management, park layout and landscape features

Increasing numbers of cities are currently developing sustainable policies aimed at promoting urban biodiversity and ecological dynamics through the planning of green networks and the implementation of more sustainable management practices. These human activities can strongly influence environmental factors on which the organization of ecological communities at different scales depends. Thus, it is of fundamental importance to understand the relative impact of local management, green space design and landscape features on the distribution and the abundance of species in urban areas. On the basis of 2 years of butterfly surveys in urban public parks within an extensive Mediterranean metropolitan area, Marseille (South-East France), the aim of this paper is to provide a better understanding of the effect of these three environmental scales (plot, park, landscape) on the composition and organization of species assemblages. Using variation partitioning and nestedness analysis on ecological data aggregated at plot-level and park-level respectively, we demonstrate the preponderant effect of landscape scale features on urban butterfly assemblages. Our results also highlight an important co-variation of plot management, park layout and urban landscape features, in their interaction with the community structure of urban butterflies. Although there is no significant species-area relationship, significantly nested patterns arise in species composition. Selective colonization appears as a driving force constraining the constitution of species assemblages within the city. However, a prospective study on adjacent more natural areas suggests that biotic limitations, interspecific competition and habitat filtering may play an important role if a larger portion of the urbanization gradient is explored, which remains to be investigated

Origin of the 26-25 Ma flood basalts from Mont Havergal, northernmost Kerguelen (South Indian Ocean)

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Origin of the 26-25 Ma flood basalts from Mont Havergal, northernmost Kerguelen (South Indian Ocean)

International audienc

How butterfly communities are structured and have changed in urbanized areas of Marseille: a 12-year monitoring survey

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Diversité de la flore cultivée des jardins privatifs du parc naturel régional du Luberon: le cas de la commune de Lauris (Vaucluse)

National audienceThe increasing urbanization of rural districts in the last thirty years led to a development of residential zones around village cores. Many exotic and local horticultural species are planted in the gardens and contribute to Flora diversity of urban and periurban areas. We described this flora in and around Lauris Town (Vaucluse, France) along a gradient of urbanization. Flora high diversity included 573 horticultural species on 21,5 ha of gardens. Most of the introduced species are from Asia, America and Europe. Those from the Mediterranean Basin accounted for 12 % of the species and are mainly Nerium oleander, Olea europea, Cupressus sempervirens, Lavandula angustifolia, Rosmarinus officinalis and Viburnum tinus. Twenty one among garden introduced species are at present considered as potentially invasive in Mediterranean regions. Variations of the Flora composition were observed along the urnunazation gradient. Gardens of the strong housing density area presented a dominance of chamephytes (28 %), a strong proportion of therophytes (11 %) and many South-African species. Areas with average and low building density have a higher proportion of ligneous shrubs and trees, between 2 and 30 m in height. In former agricultural areas, the canopy density increases and Pinus halepensis is replaced by introduced horticultural species. Urban density, horticultural practices and landscape must be taken into account to understand flora distribution and diversity in urban areas.L'urbanisation croissante des communes rurales dans les trente dernières années a conduit à un essor des zones résidentielles autour des noyaux villageois. Les jardins privatifs de ces zones constituent des lieux d'introduction d'espèces horticoles exotiques et locales qui contribuent fortement à la richesse floristique des zones urbanisées. Nous nous sommes attachés à décrire cette flore au niveau des jardins de la commune de Lauris (Vaucluse, France) selon un gradient d'urbanisation. Nos résultats montrent la forte richesse floristique de ces espaces puisque 573 taxa horticoles ont été inventoriés sur 21,5 ha de surface de jardin. La plupart des taxa introduits sont originaires d'Asie, d'Amérique et d'Europe. Les taxa du Bassin méditerranéen sont représentés à la hauteur de 12% et les plus fréquents sont Nerium oleander, Olea europea, Cupressus sempervirens, Lavandula angustifolia, Rosmarinus officinalis et Viburnum tinus. Vingt et un taxa introduits dans les jardins sont actuellement signalés comme invasifs avérés ou potentiels en région méditerranéenne, augmentant le risque d'invasions biologiques. Des variations de la composition floristique sont également observées le long du gradient d'urbanisation. Les jardins de la zone de forte densité de bâti présentent en effet une strate chaméphytique développée (28%), une forte proportion de thérophytes (11%) et un grand nombre d'espèces sud-africaines. Les zones de moyenne et de faible densité de bâti regroupent des jardins avec une strate arborée haute comprise entre 2 et 30 m. On observe ainsi une fermeture du milieu en zone agricole et une substitution de Pinus halepensis par des espèces arborées horticoles en zone forestière. Les facteurs structuraux du jardin, les pratiques horticoles et les éléments paysagers apparaissent déterminants dans l'explication de ces variations et méritent donc un intérêt tout particulier pour la compréhension des mécanismes de répartition des patrons floristiques existants

Relative importance of habitat and landscape scales on butterfly communities of urbanizing areas

Agricultural decline and urbanization entail rapid alterations of the patterns of organization of rural landscapes in Europe. The spread of the urban footprint to the adjacent countryside contributes to the development of new anthropogenic ecosystems in formerly rural hinterlands. In this study, butterflies are considered as biological indicators of these rapid environmental changes. Our purpose is to better understand changes in biodiversity related to the evolution of available habitats in a mutating landscape. In this study, we investigate butterfly communities of four land-use types (fallow lands, gardens, vineyards, woodlands) within different landscape contexts. Our results reveal that variations in structure and functional composition of these communities are related to different levels of human disturbance at both landscape scale and habitat scale

The 28 Ma Mont-Havergal flood basalts sequence : insight into old flood basalt genesis on the Kerguelen Archipelago (South Indian Ocean)

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Biodiversité et périurbanisation dans le parc naturel régional du Luberon

One of the goals of the Long Term Ecological Research Site "Mediterranean back country" is to deal with the impact on biodiversity of changes in land development and management. Urbanization of rural areas in Luberon regional Park creates complex and fast moving interfaces between agriculture, urban areas and forest. New landscape patterns are created, including natural forest remainders fragmented by housing developments, agricultural land, fallows and natural afforestation due to agricultural land abandonment, private and public gardens linked to scattered houses and urban cores. In this region, urbanization favours the development of a serious disease, leishmaniasis: it increases vector insect breeding and resting places, and bridges vector and hosts. This project is original because it studies biodiversity (plants, lepidopterans~) in the whole habitats of the periurban complex (forests, agricultural areas, fallows, gardens~) and not only in the remainders of natural or forest habitats.La Zone Atelier "Arrière Pays méditerranéen" s`intéresse à l`impact des changements de gestion et d`occupation du territoire sur la biodiversité. L`urbanisation des communes rurales dans le parc naturel régional du Luberon crée des interfaces complexes agriculture-urbain-forêt, en évolution rapide. On observe une nouvelle mosaïque paysagère regroupant: -des forêts fragmentées et éclaircies liées au "mitage" par les maisons, -des friches agricoles et des boisements spontanés liés à la déprise agricole, -des espaces verts très artificialisés privés et publics liés à l`urbanisation dense. Dans cette région, l`urbanisation favorise le développement d`une maladie grave, la leishmaniose: multiplication des gîtes d`insectes vecteurs, mise en contact des vecteurs et hôtes. Ce projet a l`originalité d`étudier la biodiversité (végétaux, lépidoptères) dans l`ensemble des habitats du complexe périurbain (forêts, zones agricoles, friches, jardins,~) et pas seulement dans les reliques de milieux naturels ou forestiers