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Impact du processus d'urbanisation sur la connectivité fonctionnelle et la diversité génétique dans les agglomérations genevoise et marseillaise
| Content Provider | Semantic Scholar |
|---|---|
| Author | Rochat, Estelle |
| Copyright Year | 2014 |
| Abstract | Over the past few decades, population growth, urbanization and intensified agricultural practices have led to the degradation of (semi-) natural areas. These landscape changes lead to fragmentation, degradation or loss of habitats. These processes reduce functional connectivity, species diversity, population size and genetic diversity and thus have an adverse effect on biodiversity in urban areas. In this context, this project aimed to study the impact of urbanization processes on functional connectivity and genetic diversity in two densely populated areas in Switzerland and France. The first part focused on the Grand Geneva area and aimed to make an assessment of the current connectivity between green spaces, for the plant Plantago major (Broadleaf plantain) and for the butterfly Pieris rapae (Small white), two frequent species in urban areas and selected as biological model for this study. The aim was also to estimate the impact of future urbanization projects planned until 2030 in the Grand Geneva area (constructions and road projects) on the functional connectivity network. The analyses were based on land cover data to create resistance maps and compute leastcost paths, in order to model the movement of individuals based on these landscape features. Landscape networks (i.e. functional links between habitat areas), were calculated in order to identify regions with reduced connectivity and thus potentially isolated green spaces. Potential dispersal barriers for the study species were identified to be mainly buildings, roads, but also large areas of forests, crops and vineyards. In addition, this study showed that the connectivity between small green spaces in the urban centers and larger ones in peripheral areas is fragile and unstable. Therefore it is important to preserve or recreate species dispersal corridors with the aim to maintain or improve the connectivity among these green spaces. Finally, it has been shown that future construction and road projects will lead to additional degradation and fragmentation of (semi-) natural habitats and partially resulting in a decreased functional connectivity for the study species. The second part of this project aimed to analyze the impact of urbanization on the spatio-temporal evolution of the genetic diversity of the butterfly P. rapae in the region of Marseille. Four transects leading from the periphery to the center of Marseille were defined and used to delineate areas with different urban densities. The evolution of populations and genotypes over time was simulated based on species-specific dispersal, mating, mutation and mortality parameters. Genetic diversity was then calculated along the transects and compared among areas with different urban densities. Two scenarios were considered for this study : 1) Individuals of P. rapae were homogeneously spread throughout the study area when starting the simulations ; 2) Individuals of P. rapae were not present in central urban habitats in order to simulate migration from the periphery towards the city center. For both scenarios, the results showed a decrease in genetic diversity in areas with a high urban density (i.e towards the city center), but the difference was more pronounced in the second scenario (migration of individuals). Simulations were also performed for butterfly species with lower dispersal abilities, and taking into account the effect of future intensification of urbanization. For both cases, simulations resulted in a reduced number of P. rapae individuals and in a decline of genetic diversity in areas characterized by medium to high urban densities. In order to conserve and promote genetically stable and diverse populations, it is therefore important to maintain or increase landscape connectivity, especially between green spaces in dense urban centers and those in more natural peripheral areas. These considerations should be taken into account when planning new urbanization projects in order to promote a sustainable urbanization process. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://documents.epfl.ch/groups/l/la/lasig-unit/www/pdm/ERochat_PDM2014.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
