1. Affiliations (1) Dept. of Biology, Santa Clara Univ.; (2) Dept. of Biology, Sonoma State Univ., (3)Univ. of California White Mountain Research Station Elizabeth Dahlhoff (1), Nathan Rank (2), John Smiley (3) GENETICS, PHYSIOLOGY AND ECOLOGY OF SUBALPINE BEETLE POPULATIONS: RESPONSES TO CLIMATE CHANGE Beginning in 1981, we have studied changing populations of the leaf beetle Chrysomela aeneicollis, feeding on willow shrubs (Salix spp.) at 2375-3550m above sea level in the Eastern Sierra Nevada mountains, California. During 25 years of observation we have observed range expansion and contraction during at least two wet-dry cycles, along with other changes. In 1988 we began sampling beetles at sites in three drainages (Rock Creek, Bishop Creek and Big Pine Creek) which revealed genetic variation across temperature gradients and elevations. In 1998 we began continuous monitoring of Salix habitat temperatures and snowmelt dates in these same drainages. These long term data sets, along with numerous other studies of the beetles’ predators, ecology, behavior, physiology and genetics, have revealed a complex and unusually complete picture of changing insect populations in high mountain environments. Findings Drainage-dependent air temperature differences, superimposed on a complex altitudinal gradient. Summer air temperatures lethal to beetles, with corresponding differences in mortality. Expansion and contraction of beetle populations during wet/dry cycles Beetle populations shifted upwards in elevation in BPC, the warmest drainage, during recent warm dry years, but that this altitudinal shift did not occur in RC or BC. Beetle abundance is lower in RC, the coolest drainage, than BC or BPC. Populations of the specialist hunting wasp Symmorphus cristatus, one of the beetles’ principal predators, have shifted upwards in elevation. We have also measured temperature- related foraging success for this wasp. Elevation Gradient and Climate Change Air Temperatures and Snow Pack Genetics, Physiology and Evolution Big Pine Creek 1981-present Bishop Creek 1988-present Rock Creek 1988-present beetle abundance peaks at 3200m in BP and 3000m in BC and RC. wet drywetdrywet? beetle elevation range expands during wet periods and contracts during dry periods. has there been an upward expansion since 2000? Study site drainages (arrow points north) Predation S. cristatus hunting success (reduced hunting time) depends on prey abundance and air temperatures. Since 2000, wasp has colonized sites above 3100m (upper edge of green zone) in BPC. Plans for 2006-2015 Using the University of California White Mountain Research Station (WMRS) as a base of operations, we plan to continue and expand these studies for at least 10 more years, funding permitting: Monitor air temperatures and humidity along four elevation gradients (add North Lake-Piute Pass drainage) and relate them to fluctuations in abundance of C. aeneicollis and two specialist predators S. cristatus and P. melanderi. Quantify variation in physiological response to temperature in C. aeneicollis and its predators. Survey changes in frequency of phosphoglucose isomerase (PGI) in a drainage where PGI is polymorphic. Quantify effects of climate on S. cristatus ecology and behavior. Make weather and insect abundance data available on the WMRS web site www.wmrs.edu This work provides a unique opportunity to integrate studies of the mechanisms underlying population change with comprehensive data on climate, for native insect species in physically challenging environments. These graphs show how PGI frequencies evolve (selection coefficient) as a function of temperature, and how selection is reversed in the later stages Elevation color bands: 4000-4250m light gray 3750-4000m light blue 3500-3750m blue 3250-3500m blue-green 3000-3250m green 2750-3000m yellow-green 2500-2750m tan 2250-2500m light tan 2000-2250m yellow North Palisade Peak survival of beetle larvae improves if predators are excluded wasp: Symmorphus cristatus (Hymenoptera: Vespidae) Fly: Parasyrphus melanderi (Diptera: Syrphidae) beetle: Chrysomela aeneicollis Coleoptera: Chrysomelidae Rock Creek was the coolest drainage, and Big Pine Creek the warmest. The coolest drainages often had the longest-lasting snowpack. Willow foliage air temperature: After factoring out elevational differences using ANCOVA, mean daily minima increased through the summer. In all 3 drainages, June was the most likely month to experience sub-zero temperatures. Frequency of phosphoglucose isomerase (PGI) allele 1 declines with elevation in Bishop Creek, yet increased at all sites between 1988 and 1996. PGI-1 allele is associated with increased expression of heat shock proteins (HSP70), which protect against cold temperatures. PGI-4 confers increased tolerance to high temperatures (CT max critical thermal maximum) Some examples of our work… Some examples of our work…. yellow dots = Salix foliage air temperature loggers orange dots = loggers planned for 2006