Sink strength and clone size of sympatric, gall-forming aphids

The supply of carbohydrates to growing galls of four species of aphids (Pemphigidae: Fordinae) that co-exist on Pistacia palaestina trees was studied. Using 14C labelling we compared the sink strength of the gall of each species for its ability to manipulate the normal phloem transport from different sources. The results indicated that none of the galls had net photosynthetic ability and all of them imported assimilates according to their specific sink strength. The data also demonstrated a correspondence between the ability of galls to draw assimilates from wider sources (sink strength) and aphid reproductive performance. Furthermore, preliminary observations indicated that species which are stronger sinks have a negative impact over other galling aphids on the same leaf or shoot through withdrawal of assimilates and nutrients.