Date: 3/30/99

Time: 8:45

Type: Symposium

Number: 103

Effects of habitat patch size, isolation, and fire history on the Homopteran communities of 8 prairie remnants in south central Wisconsin

*R. Henderson, Wisconsin Department of Natural Resources, DNR Research Center, Monona, WI 53716
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There has been rising concern that the use of fire in managing small, isolated prairie remnants may adversely affect leafhoppers and other prairie specialist insects. In an attempt to address this issue, an analysis was made of a quantitative collection of Homoptera specimens that had been gathered during the course of a spider community study conducted in 1986-87 by UW-Madison graduate student Antje Lisken. The work was done on 8 dry prairie remnants in south central Wisconsin that ranged in size from 0.2 to 42 acres. The collections were made using standardized sweepnet, pitfall, and D-Vac methods. The data were analyzed for effects of remnant size, average fire-return-interval (1 to 5 years), time-since-last-fire (0 to 4 years), and fire extent (all or part of a site burned) on numbers of individuals, species richness, and species diversity. The analysis was done on all native species combined and on prairie specialist species as a sub-group. The more prevalent of the specialist species were also analyzed individually. The data set revealed no clear effects of fire history on numbers, species richness, or species diversity. Remnant size had no effect on numbers or species diversity, but species richness of prairie specialists was positively correlated with remnant size. Only two of the 9 prairie specialist leafhoppers analyzed (Flexamia albida and Scaphytopius cinereus) showed any indications of possibly being sensitive to remnant size and time-since-last-fire. They both tended to be more prevalent on larger sites and on areas that had gone the longest without fire, but they were still detected on some of the smaller sites and on the most recently burned sites. Average fire-return-interval seemed to have no effect on any specialist species. This data set, however, is limited. Had a larger sample been available that included sites with a wider range of sizes and burn histories, the results may have been different. Also, there are so many variables to control for in this type of analysis that a sample size of at least 40-50 sites would be needed to sort out interactions among variables that may be obscuring more subtle findings. However, if fire were exerting a strong and widespread adverse influence on the prairie Homoptera community, this data set is large enough that such an effect should have been detectable. Therefore, adverse effects, if they occur, are likely limited to a relatively small group of Homoptera species, some of which, however, may be of high conservation concern.

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