LANDSCAPE-LEVEL PHENOLOGY OF A THREATENED BUTTERFLY - A GIS-BASED MODELING APPROACH

Phenology of organismal development varies between growing seasons acc ording to the weather and also varies within growing seasons across to poclimatic gradients. Combining these factors is necessary to predict landscape-level patterns of phenology and their consequences for popul ation dynamics. We developed a model on a Geographic Information Syste m (GIS) that predicts phenology of adult emergence of the threatened B ay checkerspot butterfly across complex terrain under variable weather . Physiological time was modeled by accumulated slope-specific direct insolation. Insolation sums through growing seasons were calculated fo r each cell of a digital terrain model (skipping over cloudy days) unt il a threshold for adult emergence was reached. Emergence times of adu lt butterflies for a given year were then mapped out across a 100-ha a rea. To generate predicted emergence curves for the population in a gi ven year, these maps of emergence times were then modified by incorpor ating microdistributions of postdiapause larvae. Differ ent larval mic rodistributions changed both the magnitude and shape of emergence curv es under the same yearly weather and could change mean population-wide emergence dates by 11 days. Reproductive success in this butterfly is strongly dependent on the timing of adult emergence, and these models provide insights into the effects of weather, topography and populati on history on population dynamics. Because adult emergence phenology i s often a key component of reproductive success for insects, understan ding the components of phenological variation in space and time in com plex terrain may provide insights into population dynamics for managem ent of pests and conservation of rare species.