A countrywide survey of colour morph frequencies in the spider Enoplognatha ovata (Glerck) (Araneae: Theridiidae): evidence for natural selection

Data on the frequencies of the main colour morphs ( lineata, redimita and ovata ) of Enoplognatha ovata have been collected from a total of 454 Ordnance Survey 10 km squares distributed throughout Great Britain. Only c. 0.5% of samples were monomorphic, for lineata in each case. Multiple regression analysis has been used to assess possible associations between morph frequencies and principal components derived from nine environmental variables. The distribution of morph frequencies is not random but shows weak clines associated with certain climatic factors. These large scale clines indicate the action of natural selection although very local variations in morph frequencies may result from selection and/or drift.