Population dynamics and dispersal of a cultivated species escaped from fields :
feral oilseed as a case study
Simulation models, statistics and genetics


Aurélie Garnier
Laboratoire Ecologie, Systématique et Evolution
Bat 360, Université Paris Sud-11
91405 Orsay Cedex
FRANCE
Supervisor: Jane Lecomte

web page in English



Cultivated species escaped from fields

Understanding and quantifying gene flow at the landscape scale is a question of growing interest, especially in the case of farming landscapes. Gene flow arising among fields, wild/weed and feral populations is a much complex phenomenon and raises a large diversity of questions dealing with genetic pollution, long-distance dispersal, impact of human activities, changes in biodiversity... Due to the fragmentation of the habitat, especially pronounced in farming landscapes, population dynamics exhibit complex metapopulation patterns, especially in the case of cultivated species escaped from fields and established in field margins. These feral populations coexist with crops and exchange pollen and seeds. Crop-feral gene exchanges could lead to several environmental and economical issues:
- Advantageous genes (i.e. increasing plant fitness) could escape from fields into feral populations and increase the weediness of these populations. Such "super weeds" could be a problem for farmers and threaten the biodiversity within road verges by overcompeting local plants. This risk is particularly high in the case of herbicide tolerance and pest resistance (transgenic or conventional).
- feral populations could make less feasible farm isolation (GM, non-GM, organic farms...) by increasing feral-crop gene exchanges.

Feral oilseed rape as a case study

We chose oilseed rape as a model species to study gene flow at the landscape scale. Oilseed rape is indeed a high risk species: feral populations are abundant and transgenic cultivars have been developed for this species. This PhD divides into two main axes: Population dynamics and population genetics. I intend ti answer the following questions:
- What are the population abilities to persist and disperse?
- Which factors govern population dynamics and spread?
- What are the distance covered by seeds before establishment in a feral population

I use several different approaches: simulation models, statistical analyses of field data (demography and genetics - microsats), experiments in natural conditions.