Lateglacial and Early Holocene insect assemblages from sites at different altitudes in the Swiss Alps—implications on climate and environment

Insect analyses from four sites at different altitudes in the Swiss Alps are presented. The dominant insect group considered here is Coleoptera (beetles), though other insect orders are also recorded. The study includes the first detailed insect records dating to the Younger Dryas in Switzerland. The quantitative climatic reconstructions based on coleopteran assemblages were made using the MCR method. Mean temperatures of the warmest month similar to modern intensities are indicated at the end of Allerød interstadial (AL) and at the beginning of the Holocene (PB). The winters during the AL were rather colder, implying more continental conditions than at present. During the Younger Dryas stadial (YD), the mean temperatures of the warmest month were 5–8°C colder than those of the present day, and the mean temperatures of the coldest month were about 10–12°C colder than today. A rapid change in the faunal composition was found at the Gerzensee and Zeneggen sites during the transition YD/PB. The change is characterized by the disappearance of cold-adapted species between two contiguous samples (i.e. within 1.0 cm of sediment sampled). At Gerzensee, the cold-adapted species assemblage was immediately replaced by temperate species. The Coleoptera thus indicate extremely rapid and intense climatic oscillations at the Lateglacial–Holocene transition.