Phylogenetic affinities of tarsier in the context of primate Alu repeats

Related genomes tend to be colonized by the same or similar repetitive sequ ence elements. Analysis of these elements provides useful taxonomic informa tion. We have sequenced Alu repeats from tarsier and compared them with tho se from strepsirhine prosimians (lemurs, sifaka, and galago) and the human genome. Tarsier elements cluster with Alu subfamilies from the human lineag e. The oldest subfamily in tarsier and the most abundant human subfamilies share an RNA secondary structure motif which is absent both in the earliest dimeric Alu do and in the strepsirhine elements. These findings are consis tent with the view that tarsiers form a sister clade with anthropoides rath er than with other prosimians. Alu repeats in tarsier genome are relatively old, which indicates a dramatic slowdown or even an arrest of these elemen ts' amplification about 20 Myr ago.. (C) 1999 Academic Press.