Spatial and temporal genetic variation in British field populations of the grain aphid Sitobion avenae (F.) (Hemiptera: Aphididae) studied using RAPD-PCR.

The grain aphid Sitobion avenae (F.) was collected from winter wheat and adjacent cocksfoot grass at two locations in southern England and at four times in the year (April-July). Genetic variation between individual aphids was then investigated using random amplified polymorphic DNA polymerase chain reaction. Individuals caught in wheat and cocksfoot during April provided very different and highly diagnostic banding patterns that were independent of location. This host-based genetic differentiability was less evident as the season progressed, largely as a result of genetic drift and local movement between adjacent host species, which appeared to be predominantely in the direction from cocksfoot to wheat. The diversity of putative clones fell significantly, the mean number of individuals per clone rose and clones became more exclusively associated with certain sites which suggests that long-distance migration may have less of a homogenizing effect than hitherto thought for this species.