Holocene mean temperatures derived from beetle studies in the Abisko area, N Sweden [email protected] [email protected] [email protected] This lecture • Insects respons to climate change • Mutual Climatic Range method (MCR) • Holocene MCR data from Lake Tibetanus, Abisko, N Sweden • Other climate records from the same area Green tiger beetle (Cicindela campestris) • Larvae and adults are exclusively carnivorous generalists • Cold-blooded • Habitat: sandy ground with sparse vegetation • Open, warm, sun exposed environments Insects and climate • Climate often limits insects geographical distribution • Arctic to temperate areas – Temperatures sets the limits • Stenothermic species – Species adapted to a narrow temperature span Where are insect remains found? Ca 5000 year old insect remains in peat from a bog in Småland • Preserve well in wet/moist environments • Natural deposits • lake and fluvial sediments • Carr and bog peat Beetles (Coleoptera) • Robust exoskeleton – Body parts of adults – Identification to species level • Diverse adaption to both terrestrial and aquatic habitats • Many stenothermic species – Predators, scavengers genaralists Climate reconstructions • Mean temperature reconstructions – Mutual Climatic Range method (MCR) • Mean temperature of the warmest month (TMAX) • Mean temperature of the coldest month (TMIN) • Difference summer/winter temperatures (TRANGE) • Changes in humidity Geographical distribution → Climatic range • Atkinson et al. 1987. Nature 352:587-592 • Data from metereological stations • Geographical space is translated to temperature range • Climate envelopes for each species • Data base of climate envelopes Elias 2007 Climate envelopes Elias 2007 • Stenothermic beetle species recorded in a sample • Envelopes stacked • Overlapping range represent the temperature reconstruction • This is the climate range were all species may coexist MCR results • Tests on modern beetle assemblages adjacent to weather stations – Acceptable accuracy of reconstructed temperatures • Slight underestimation of Tmax and Tmin of the coldest temperatures • Regression equations – Calibration of mean values • Jack knife method Abisko Lake Tibetanus 560 m a.s.l. Lake Njulla 999 m a.s.l. Barnekow 1999 MCR results from Lake Tibetanus Macroscopic plant remains from L Tibetanus Barnekow, L. 1999. The Holocene 9:253-265 Barnekow 1999 Lake Njulla 999 m a.s.l. • Diatom assemblages (July temp) • Chironomid assemblages July temp Bigler et al. 2003. J of Paleolimnology 23:13-29..