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Oak Species Attributes and Host Size Influence Cynipine Wasp Species Richness
Author(s) -
Cornell Howard V.
Publication year - 1986
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1939089
Subject(s) - species richness , ecology , biology , fagaceae , lobata , body size and species richness , global biodiversity , biodiversity , species diversity , medicine , alternative medicine , pathology , pueraria
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 support the same species as the lower canopies, and only two species tend to associate exclusively with smaller trees. Instead, those species found in smaller trees are either random or nonrandom subsets of those in larger trees. The latter pattern I term hierarchical association. The total number of cynipine species associated with each oak species (regional richness) varies widely among the five oaks and correlates significantly with cynipine richness on individual trees in multiple regressions with tree size. Path analysis indicates that regional richness is correlated with richness on trees exclusively through increasing the species pool from which the assemblage on individual trees in drawn. This pattern represents a reversal of cause and effect from that predicted by vertical and horizontal zonation, and suggests that appropriate explanations for richness variation among host plants must address processes that occur over large geographic scales as well as local interactions on hosts.