Determining connectivity within complex landscapes is difficult if habitats that facilitate dispersal differ from habitats where animals normally are found or enter. We addressed the question of how landscape features affect dispersal by quantifying two critical aspects of animal movement behavior that determine dispersal rates across complex landscapes: conductivity of major habitat types and behavior at boundaries between habitat types. Our tests consisted of behavioral experiments and observational surveys of a wetland butterfly, Satyrodes appalachia. Displacement rates varied among habitats, with the longest moves and straightest paths leading to greater displacement rate in open habitat and shortest moves and most sinuous paths causing the slowest displacement rate in riparian forest habitat. We found a strong negative relationship between the probability of entering a habitat and the speed of moving through it. Recognizing this central conflict between entering and moving through habitat is important for assessing the connectivity of complex landscapes.

Determining population viability of rare insects depends on precise, unbiased estimates of population size and other demographic parameters. We used data on the endangered St. Francis' satyr butterfly (Neonympha mitchellii francisci) to evaluate 2 approaches (mark-recapture and transect counts) for population analysis of rare butterflies. Mark-recapture analysis provided by far the greatest amount of demographic information, including estimates (and standard errors) of population size, detection, survival, and recruitment probabilities. Mark-recapture analysis can also be used to estimate dispersal and temporal variation in rates, although we did not do this here. Models of seasonal flight phenologies derived from transect counts (Insect Count Analyzer) provided an index of population size and estimates of survival and statistical uncertainty. Pollard-Yates population indices derived from transect counts did not provide estimates of demographic parameters. This index may be highly biased if detection and survival probabilities vary spatially and temporally. In terms of statistical performance, mark-recapture and Pollard-Yates indices were least variable. Mark-recapture estimates were less likely to fail than Insect Count Analyzer, but mark-recapture estimates became less precise as sampling intensity decreased. In general, count-based approaches are less costly and less likely to cause harm to rare insects than mark-recapture. The optimal monitoring approach must reconcile these trade-offs. Thus, mark-recapture should be favored when demographic estimates are needed, when financial resources enable frequent sampling, and when marking does not harm the insect populations. The optimal sampling strategy may use 2 sampling methods together in 1 overall sampling plan: limited mark-recapture sampling to estimate survival and detection probabilities and frequent but less expensive transect counts.

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Abstract. Experiments in ecology can have unintended side effects. Recently, it has been suggested that the act of visiting a plant, inherent to studying herbivory, may alter plant performance and interactions. To evaluate the generality of this inference, we examined plant performance and herbivory on 14 plant species in three geographic regions. Visitation did not significantly affect any of the variables that we measured, including leaf damage, height, biomass, or survivorship, for any species. However, rates of herbivory varied significantly among sites and regions. Thus, our data do not support the generality of visitation impacting estimates of herbivory. We propose that future studies of herbivory will gain more by evaluating spatial heterogeneity in interaction outcomes than by quantifying possible experimenter-caused variation.