R-CHROMOSOME BANDING STUDY OF THE DARK FORM SOREX CORONATUS FROM WESTERN FRANCE MARSHES

The species of the genus Sorer belonging to the Sorer araneus group ar e morphologically rather similar. The extreme manifestation of the sim ilarity is the case of S. araneus and S. coronatus which can only be d istinguished unambiguously by chromosomal, electrophoretical or molecu lar analyses. The existence within some western French populations of S. coronatus of two colour forms, typical and dark, regarded as two su bspecies, stimulated the present study. The two forms occur in equal p roportions and seam to be sympatric in the western French marshes situ ated in the north of Rochefort city. A R-banding chromosome analysis r evealed that the karyotypes of these two sub-species are similar and c haracterised by 20 autosomes with identical arm combination and by sim ilar sex chromosomes. Our study casts doubts on the subspecific status of the dark form and indicates the necessity for caution when using c olour differences in the systematics of the S. araneus species group.