Oak Species Attributes and Host Size Influence Cynipine Wasp Species Richness

The number of kinds of cynipine wasp species associated with trees of different size were evaluated for five oak species endemic to the Pacific Slope to California. Species counts were taken on 357 trees during July and August of 1979, 1980, and 1981. Different oak species support significantly different numbers of cynipine species on tree of a given size. Within oak species, tree height and the number of cynipine species available to colonize trees explained 0.024—58% of total variation in cynipine richness among trees. Tree height was generally the strongest correlate with significant height—richness regressions for four of the five oak species examined, but cynipine species pools also made significant contributions on three oak species. The height—richness correlation was intensively examined over three seasons on one oak (Q. lobata) and remained stable even though species composition changed from year to year. There is no evidence of vertical or horizontal zonation in this system. Upper tree canopies ...