Population sizes and within-dome movement of Trimerotropis saxatilis (Acrididae), a grasshopper with a fragmented distribution

Capture-mark-recapture studies were initiated in 1990 on four Missouri populations of the lichen grasshopper, Trimerotropis saxatilis. This grasshopper lives only on glade habitat, predominantly in the Ozark Mountains. Genetic data suggest that no gene flow occurs among T: saxatilis populations. Lichen grasshopper population size (both present and historical), and the likelihood of movement within and between glades, are the subjects of this study. Population sizes on all glades were found to be small (<280 individuals) and to vary from year to year. Inbreeding effective sizes were found to be much larger than census sizes. On one bf the sites, Graham Cave Glade, population size was calculated for 5 years; in 3 of those years (1991, 1993 and 1994) our studies of this population also tested for move,ment of T saxatilis individuals among different regions of the moderately subdivided glade. Maintenance of Graham Cave Glade (burning and clearing) was initiated after the 1991 capture-mark-recapture season. Comparisons of before-and after-burning intraglade movement probabilities did not show a significant difference. Grasshoppers more frequently remained in the part of the glade where they were previously captured, but were able to move about the moderately subdivided glade. The presence of a closed-canopy forest, rather than distance, appears to be an effective dispersal barrier.