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Canopy herbivore community structure: Large-scale geographical variation and relation to forest composition

par Franklin, Anne ;Liebhold, Andrew A.M.;Murray, Kathleen;Donahue, Charlene
Référence Ecological entomology, 28, 3, page (278-290)
Publication Publié, 2003-06

Article révisé par les pairs

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Résumé :

1. Geographical distributions of individual foliage-feeding forest herbivore species have been found to be aligned closely with the distribution of their host trees, however little is known about the extent to which broad herbivore communities are geographically associated with distinct host communities. 2. Large-scale geographic variation in canopy herbivore communities in a 80 000 km2 area (the state of Maine, U.S.A.) was characterised using historical insect survey data. Variation in insect communities was compared with corresponding variation in forest over-storey composition, which was quantified using data from a regional forest inventory survey. 3. Principal components analysis was used to characterise associations among herbivore and tree species. Analysis of the herbivore data identified three main insect groups: group A corresponded to a single species (Choristoneura fumiferana), group B corresponded to pine-feeding species including Semiothisa sp., and group C corresponded to the spruce-feeding species Gilpinia hercyniae and Pikonema alaskensis. Analysis of the forest inventory data characterised three important forest types: northern hardwoods, eastern white pine, and northern spruce-fir forest types. 4. Spatial analyses were carried out on the first two components of each of the principal components analyses. Factor 1 of the insect data showed a trend of decreasing values from south to north, while factor 2 of the forest inventory data showed an opposite trend. These inverse trends reflected the distribution of the main contributing species to the principal components analysis, C. fumiferana and Pinus strobus respectively. These distributions were highlighted further by the significant negative cross-correlations that were found between the two factors up to distances of 120 km. 5. Analyses indicated a parallel between the geographic variation in the insect guilds associated with conifers and the geographic pattern of their conifer hosts. Hardwood-feeding caterpillars, on the other hand, did not form well-defined guilds and showed varying geographical distributions. The survey data showed varying quality in defining large-scale associations in the structures of herbivore and host communities. 6. Implications for biodiversity management are discussed.