Refining mutual climatic range (MCR) quantitative estimates of palaeotemperature using ubiquity analysis

Abstract

The Mutual Climatic Range (MCR) method, originally developed in the early 1980s to derive quantified palaeotemperature estimates from fossil beetle assemblage data, is based on assessments of the relationships between the modern distributions of beetle species and instrumentally measured climatic gradients. However, the MCR approach is based on presence/absence beetle data only, with no information on the spatial variation in relative dominance/importance of beetle species within their present climate ranges. This means that beetle–climate relationships are more difficult to test using conventional, probabilistic statistical methods. It is also unlikely that beetles have a normal (Gaussian) distribution in climate space, and hence calibration methods developed for correcting MCR values for bias in raw data are also questionable. In this paper, the underlying statistical weaknesses in the MCR method are examined, while an alternative approach, Ubiquity Analysis, is introduced. It is concluded that this approach offers much potential for reducing the uncertainties associated with MCR estimates.