Magali Deschamps-Cottin

Gardens in urbanizing rural areas reveal an unexpected floral diversity related to housing density

The increasing urbanization of rural areas leads to a strong development of horticultural flora, which is the main source of alien and invasive plants. In order to assess the pool of cultivated species under different urbanization pressures, the diversity and distribution of horticultural flora were studied in 120 Mediterranean gardens belonging to three housing density types. The results showed a great richness and heterogeneity of this flora, and similarities in species composition between gardens of the same housing density types. Twenty-four percent of the cultivated species are well adapted to the Mediterranean climate, and 21 species known to be invasive on the French territory have emanated from gardens. Inventorying areas adjoining gardens would be useful in identifying escaped garden plants and to assess the associated risks for biological diversity. The results also suggested a detailed analysis of the influence of social, economic and regional factors on planting practices, in order to identify the drivers of these original floral patterns.

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.

Valeur trophique des plantes nourricières et préférence de ponte chez Parnassius apollo L. (Lepidoptera, Papilionidae)

Resume Espece montagnarde, protegee par la Convention de Washington (Cites), Parnassius apollo , lApollon, est en regression ou eteint dans beaucoup de massifs montagneux europeens. La definition des facteurs ecologiques, en particulier trophiques, qui conditionnent son maintien est importante pour mettre au point des mesures de conservation. Oligophage, la chenille de lapollon consomme diverses especes de Crassulacees. Les resultats dobservations et dexperiences sur les preferences de ponte des femelles et la valeur trophique de diverses plantes sont exposes ici. Les deux especes les plus frequemment citees comme plantes nourricieres, Sedum album et S. maximum , se sont revelees les plus efficaces. Dautres especes de Crassulacees frequemment mentionnees ont ete refusees ; une autre, acceptee, a assure un succes mediocre a lelevage. Une comparaison avec dautres cas de specificite trophique chez les Lepidopteres est effectuee et les implications de ces resultats dans les mesures de conservation sont discutees.

Hybridation et introgression entre « bonnes espèces ». Le cas de Parnassius apollo et P. phoebus

Two butterfly species living in the Alps, Parnassius apollo and P. phoebus, frequently hybridize in certain localities of this region. The features of this phenomenon have been previously studied by biometry and starch gel electrophoresis, but some points remained obscure. We present them in a study combining results from cellulose acetate electrophoresis and wing pattern biometry with a determination of the mitochondrial haplotype by a PCR-RFLP analysis in a sample of butterflies from the southern French Alps. It was already known that the male hybrids are fecund and thus that interspecific gene exchange could take place via backcrosses with the parent species. In the present case, combining the identification of mtDNA with the analysis of nuclear genotypes allows us to demonstrate that hybridization can involve both sexes of both species. Moreover, it suggests that at least some female hybrids are not sterile. The impact of Haldanes rule is therefore not very strong in the present case. However, although the prerequisites for introgression between the concerned species are fulfilled, at the level of both nuclear and mitochondrial genomes, no indication of such a phenomenon could be gathered in the studied sample.

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 subpart 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.