The direct and indirect effects of fire on the assembly of insect herbivore communities: examples from the Florida scrub habitat |
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Authors: | Tania N Kim Robert D Holt |
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Institution: | (1) Department of Biology, University of Florida, PO Box 118525, Gainesville, FL 32611-8525, USA;(2) Department of Biological Sciences, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306-4295, USA |
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Abstract: | Disturbance is a major source of spatial and temporal heterogeneity. In fire-maintained systems, disturbance by fire is often
used as a management tool to increase biological diversity, restore degraded habitats, and reduce pest outbreaks. Much attention
has been given to how plant communities recover from fire, but relatively few studies have examined post-fire responses of
higher order species, such as insect herbivores. Because dynamic feedbacks occur between plants and their consumers, which
can in turn influence the response of the entire ecosystem, incorporating higher trophic level responses into our understanding
of the effects of fire is essential. In this study, we used structural equation modeling (SEM) to tease apart the direct and
indirect effects of fire on insect herbivore assemblages found on three common oak species in the Florida scrub (Quercus inopina, Q. chapmanii, and Q. geminata). We investigated how fire affected herbivore abundance, richness, and community composition both directly and indirectly
through environmental heterogeneity at different spatial scales (e.g., leaf quality, plant architecture, and habitat structure).
We also investigated how seasonality and landscape heterogeneity influenced post-fire responses of insect herbivores and whether
fire effects on herbivore assemblages varied among different host plants. Our general findings were that fire effects were
(1) largely indirect, mediated through habitat structure (although direct fire effects were observed on Q. inopina herbivores), (2) non-linear through time due to self-thinning processes occurring in the scrub habitat, and (3) varied according
to herbivore assemblage as a result of differences in the composition of species in each herbivore community. To the best
of our knowledge, this is the first comprehensive study to examine how fire influences the assembly of insect herbivore communities
through both direct and indirect pathways and at multiple spatial scales. |
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