The relative abundance of Onthophagus species in British assemblages of dung beetles as evidence for Holocene climate change

Abstract

The ratio between scarabaeid beetles of the genera Aphodius and Onthophagus in European dung faunas is influenced by summer climate, such that individuals of Aphodius species predominate in Northern Europe but are largely replaced by Onthophagus species in the Mediterranean region. Detailed study of insect assemblages from Neolithic to Saxon date showed a changing ratio between the genera with time. For the Neolithic and most of the Bronze Age, individuals of Onthophagus contributed around 16% of the sum of Aphodius and Onthophagus, but during the Iron Age the proportion of Onthophagus fell to around 3% and remained low. This decline of Onthophagus was probably the result of a slight cooling of mean summer temperature and agricultural intensification. However, the proportion of Onthophagus peaked at over 60% during the middle Bronze Age around 1450 BC. This is argued as reflecting a brief warm episode with mean July temperatures for Central Southern England at least 2°C warmer than at present.