PARENT SESSION
Contributed Oral Session 15: Populations and Genetics: Succession; Reproduction
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 522 A, Level 5, Palais des congrès de Montréal
Dynamics of plant use of a pest insect in an agricultural landscape studied using isotopic and molecular analyses.
Vialatte, Aude1, 2, Rivot, Etienne1, Fabre, Frédéric1, Simon, Jean-Christophe1, Dedryver, Charles-Antoine1, Plantegenest, Manuel1, 1 Agrocampus, Rennes, France2 Makhteshim Agan, Paris, France
ABSTRACT- Agroecosystems are made of a mosaic of ephemeral habitats submitted to frequent disturbances that force pest species to colonise seasonally available crop habitats or wild margins. In this study, the dynamics of crop colonisation and the ecological specialisation of the grain aphid Sitobion avenae were studied using both stable carbon and nitrogen isotopes and genetic (microsatellites) markers. Wingless aphids were collected on eight cultivated and uncultivated host plant species (wheat, barley, oat, corn, Yorkshire fog, cocksfoot, couch grass and tall oatgrass) at a landscape scale and analysed individually for isotopes and microsatellites. Isotopic ratios differentiated aphids from C3 (majority of Poaceae) vs C4 (corn) host plants but unexpectedly also allowed to distinguish aphids from different host plant tribes (Triticeae, Aveneae, Poeae and Zeae). A bayesian model was then developed and used to identify the host plant tribe source of winged aphids colonizing wheat fields in spring and autumn. Results showed that aphids landing wheat in spring originated mainly from plants belonging to the Triticeae tribe, while corn contributed to a third of the sample in autumn. Beside, genetic analyses showed a high differentiation between populations living on uncultivated hosts and those on crops, suggesting a limited gene flow between these two types of habitats. A closer genetic relatedness was observed between populations living on plants belonging to the same tribe (Triticeae, Poeae and Aveneae tribes). Then, aphid populations appear to be differentiated at two levels: the host plant tribe and the character cultivated or not of the host. These findings evidenced the need for an integrated and ecological pest management at a large landscape and temporal scales.
Key words: host-plant specialisation, stable isotopes, landscape genetics, pest management