Complexity of leaf miner-parasitoid food webs declines with canopy height in Patagonian beech forests

DEVOTO, M.; CHAIJ, J.; MAZÍA, C.N.; CHANETON, E.J.; OLEIRO, M.

ECOLOGICAL ENTOMOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 41 p. 599 - 610

0307-6946

1. Consumer-resource species interactions form complex, dynamic networks, which may exhibit structural heterogeneity at various scales. Here we asked whether host?parasitoid food web size and topology vary across forest canopy strata, and to what extent foliar resources and species abundances account for vertical patterns in network structure.2. The vertical stratification of leaf miner?parasitoid food webs was examined in two monotypic beech (Nothofagus pumilio) forests in northern Patagonia, Argentina. Quantitative food webs were constructed for separate canopy layers by sampling foliage from three tree-height classes at 0.5?1, 2?3 and 5?6 m above ground. 3. Leaf miner abundance per unit leaf mass and foliar damage (%) did not differ across strata, although foliage quality and quantity increased from understorey to upper canopy. Parasitism rates and food web complexity decreased with canopy height, as reflected by reduced linkage richness, linkage density, mean interaction strength, and host vulnerability. 4. Null model analyses revealed that food web metrics, especially in the upper canopy, were often lower than expected for networks only structured by random host?parasitoid encounters. Overall, these patterns held for two forests differing in vertical structure, and in dominant miner morphotype and parasitoid species. 5. Our results suggest that vertical declines in network complexity may be driven by the parasitoids? functional response to host abundance and limited dispersal from pupation sites in the forest floor. A broader constrain on food web structure seemed to be imposed by host?parasitoid trait matching, a reflection of large-scale assembly processes.