Phylogenetic history of LINE-1 among arvicolid rodents

The extent of restriction fragment sharing among arvicolid rodents was examined following Southern blotting with a reverse transcriptase region probe from long interspersed nuclear element 1 (LINE-1 or L1). DNAs from 30 species belonging to nine genera were digested with 11 restriction endonucleases. Following hybridization discrete bands were scored with respect to their presence or absence and intensity, and both within- and between-species comparisons were conducted. Intraspecific analyses revealed low but detectable levels of variation. Interspecific comparisons revealed three groups of bands: those present in all 30 species (6 out of a total of 248 bands), those phylogenetically informative in two or more species (130 out of 248), and those unique to a single species (114 out of 248). A multistate data matrix consisting of species by codes representing the intensities of informative bands was analyzed by maximum parsimony. Further, distance values between species were converted to rates using estimated fossil divergence times. Both the parsimony and rate analyses revealed differences between species in the extent of band sharing and in the intensities of common bands, indicating that the amplification and movement of LINE elements has occurred in episodic bursts during the history of this group. Systematic interpretations of the evolutionary trees were concordant with those previously obtained using other data sets, suggesting that although the amplification of repetitive sequences may occur episodically in this taxonomic group, there do appear to be some constraints.