PARENT SESSION
Contributed Oral Session 8: Invertebrate Ecology: Butterflies; Soil Insects
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 518 C, Level 5, Palais des congrès de Montréal

Butterfly community phenology across an altitudinal transect.

Thorne, James^*,, Joshua, Obrien, Mathew, Forister, Arthur, Shapiro,

ABSTRACT- We modeled butterfly community phenology from a 33 year study at ten locations that form an altitudinal transect starting in the coast mountains of California and progressing over the Sierra Nevada. Our goal was to study species-specific differences in phenology and to develop a tool that would be useful for asking questions related to monitoring and management. Observations by species were regressed against a circular date that compiled all observation records from a site into 365 days. We used a quadratic logistic regression to generate a yearly cycle of rising, then falling probabilities of species occurrence (observation) for each species at a site. Daily probabilities were then summed for all species at a site to create a yearly potential species richness (PSR) curve. The maritime site had species with the longest flight periods, but only moderate PSR. PSR was highest at high elevation sites, where flight periods were shortest. Peak abundance generally occurred later at the coastal site and the high elevation sites than on the central valley floor or the Sierra Nevada foothills. Species with different numbers of broods per year, over-wintering life stages, and residency status contribute to PSR in significantly non-random ways over the course of a year. Date of first flight was significantly influenced by over-wintering stage, length of flight window was significantly influenced by number of broods. The model approach incorporates all years and all environmental variation. As such it could serve as a null model against which phenological records in unusual weather years can be contrasted.

Key words: Butterfly, Monitoring, Modeling