LEAF SIZE SELECTION BY LEAF-MINING INSECTS ON QUERCUS-EMORYI (FAGACEAE)

Leaf size selection by four species of leaf-mining insects on their host plant, Quercus emoryi, was studied in central Arizona, USA. Two species (Stigmella sp. and Tischeria sp.) that produced small mines also selected small leaves. One species, Stilbosis juvantis, which has an intermediate-sized mine, did not select larger or smaller leaves than the average leaf size available. Only one species, Cameraria sp. nov., showed a relationship between its survivorship and leaf size; it selected large leaves and experienced greater survivorship on large leaves. Survivorship of the other species was not related to leaf size. We experimentally investigated effects of density on leaf size selection by one species, Cameraria sp. nov. In previous work, density manipulations of this species resulted in density-dependent mortality and greater mortality at high density cages as a result of reduced leaf miner survivorship in singly-mined leaves. Here we show intraspecific competition was not related to size limitation of leaves; singly-mined leaves from high density cages were not smaller than those from low density cages. We suggest intrinsic variation in leaf nutritional and defensive chemistry may be important in density-dependent mortality found in Cameraria.