Genomic nucleotide variation in the ITS1 rDNA spacer of land snails.

摘要

This paper presents the results of a study aiming to analyse the extent of ITS1 variation of 4 taxonomically robust species of land snail of different family categories, i.e. Acanthinula aculeata (Valloniidae sensu lato), Arianta arbustorum (Helicoidea), Cochlodina fimbriata (Clausiliidae) and Vallonia costata (Valloniidae sensu stricto). It is shown that one species (Acanthinula aculeata) exhibits a high level of ITS1 variation, whilst another species (V. costata) displays nearly no variation. The other 2 taxa display moderate variation. The results of investigations of ITS1 rDNA for highly conserved sequence motifs and of extent of nucleotide variation within such motifs are also presented. Evolutionary conserved regions in ribosomal spacers are suspected to be involved in the maturation of the precursor rRNA. The possible occurrence of rDNA pseudogenes in PCR amplicons and genome databases is discussed..