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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #169128
Title: Patch edges and insect populations

Author
item Olson, Dawn
item ANDOW, DAVID - UNIV. OF MINNESOTA

Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2007
Publication Date: 12/21/2007
Citation: Olson, D., Andow, D. 2008. Patch edges and insect populations. Oecologia. 155:549-558.

Interpretive Summary: Existing models attempting to elucidate the influence of landscape pattern on insect populations assume homogeneity of species within a particular patch. However, patch edges and patch centers differentially affect insect species, but it is not clear how these effects translate across species or propagate in community structure. We developed a model with three types of insect response to edges: no difference at the edge or the null model, reflecting edges and absorbing edges. We then investigated several insect species' response to edges and patch size within maize plots. Insects showed a variety of responses to patch size and edges. Coleomegilla maculata, and Trichogramma spp. were the only organisms that responded to patch size and edges as patch theory and the null edge model would predict. Ostrinia nubilalis larvae and possibly R. maidis and Chrysopa spp. responded to patch size and edges as predicted by an absorbing edge model. Estimation of predation rates suggested that the spatial distribution of these species might be structured by top-down factors. Several existing diffusion-reaction models may be useful in predicting species specific responses to landscape pattern.

Technical Abstract: We simulated edge effects on theoretical patches to illustrate how insect population density could respond to patch edges. We considered three kinds of edges: In the null model, the edges have similar probabilities of insect survival, movement, direction of movement, reproduction and survival as the center of the patch. In the second model, the edges reflect individuals back into the patch, or, the direction of movement is modified at edges, but the probabilities of survival, movement within the patch, and reproduction are the same as the center of the patch. In the third model, the edges absorb individuals that move into the edge, or, the probability of movement from an edge site is less than from a central site, but the probabilities of survival, direction of movement and reproduction are the same as the center of the patch. We tested the response of several insect species to patch size and the edge and center of maize plots. The species examined included Rhopalosiphum maidis, Hippodamia tredecimpuntata, Hippodamia convergens, Coleomegilla maculata, and eggs of Chrysopa spp., O. nubilalis larvae and predation on O. nubilalis eggs. Coleomegilla maculata, and Trichogramma spp. were the only organisms that responded to patch size and edges as patch theory and the null edge model would predict. Ostrinia nubilalis larvae and possibly R. maidis and Chrysopa spp. responded to patch size and edges as predicted by an absorbing edge model. Understanding how species respond to individual patches may aid in predicting species specific responses among patches in landscape.